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Abstract: Apocrine hidrocystomas are benign, cystic neoplastic lesions resulting from the apocrine secretory component of the sweat gland. They most commonly occur on the head and neck, with predilection to the periorbital area. Less frequent sites include the axilla, nipple, external auditory canal, foreskin, conjunctiva, lower lip, and fingers, among others. The authors report a unique case of a nail bed hidrocystoma in a 55-year-old woman, a site not previously described., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2024 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Hidradenocarcinoma (HAC) is a rare adnexal tumor associated with the potential for locoregional recurrence and systemic metastasis. The clinical appearance of HAC is nonspecific, frequently presenting as a solitary firm subcutaneous nodule or plaque on the head and neck region or distal extremities. These tumors show histomorphologic heterogeneity, as they can be low and high grade. Distinguishing HAC from hidradenoma, especially the low-grade variant of HAC, can be challenging as both tumors can show histologic overlapping features. In this article, we describe a case of a 33-year-old patient presenting with a low-grade HAC of the plantar foot who was subsequently found to have lymph node metastasis., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: A 43-year-old woman presented with a palpable, pruritic, minimally painful right vulvar lesion. Physical examination revealed approximately 2.0-cm tender nodule at 70' clock in the right labia majora. Histological sections of the excision specimen showed an unremarkable epidermis with large, well-circumscribed dermal proliferation with extension to the reticular dermis. Within this proliferation are small solid and ductal structures relatively evenly distributed in the sclerotic stroma. The epithelial elements consisted of monomorphous cuboidal cells and assumed round, oval, curvilinear, or have other peculiar geometric shapes, including "comma-like" or "tadpole"-like configurations. The tumor cells were positive for CEA, EMA, and estrogen receptor and negative for progesterone receptor. The clinical presentation and the deep extension of the tumor were similar to the microcystic adnexal carcinoma. Although a syringoma generally presents with multiple lesions and usually involves the superficial dermis, a syringoma with deep extension was favored based on the lack of follicular differentiation, atypia, mitoses, and perineural invasion. Microcystic adnexal carcinoma and syringoma have a morphologic overlap and are misdiagnosed in 30% of the cases. Thus, it is exceptionally important for pathologists to be aware of and be able to distinguish these entities. To the best of our knowledge, this is the first case of a solitary, painful vulvar syringoma with deep extension., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Eccrine syringofibroadenoma (ESFA) is a rare benign skin adnexal lesion of the acrosyringium of eccrine sweat ducts. Reactive ESFA, a subtype of ESFA, is usually associated with non-neoplastic cutaneous dermatoses or neoplastic skin tumors. Clinically, the lesions can be solitary or multiple, pink, or skin-colored coalescing papules or nodules of variable sizes. Histopathologically, this tumor is composed of numerous anastomosing cords of monomorphic cuboidal epithelial cells with eccrine duct formation. The association of reactive ESFA with benign conditions, such as psoriasis, diabetic polyneuropathy, scars, and leprosy, has been reported. However, the association of reactive ESFA with malignant tumors is extremely rare, with very few cases reported in the literature. We present a case of a 72-year-old woman who developed reactive ESFA associated with Merkel cell carcinoma excision scar. The ESFA tumors developed in the area of the surgical graft 10 months after the Merkel cell carcinoma had been excised. New ESFA tumors have continued to appear in the scar on a yearly basis while, so far, has been no recurrence of the original tumor. However, the presence of new tumor growths in the area suggested the possibility of recurrence of the Merkel cell carcinoma. That possibility was enhanced by the fact that PET scans revealed hypermetabolic activity in the ESFA papules., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Sweat gland carcinoma with neuroendocrine differentiation (SCAND) is a newly proposed tumor entity of primary cutaneous apocrine/eccrine adnexal tumor with neuroendocrine differentiation. The histopathologic variations are not yet well known. In this article, we present a case of SCAND mimicking male breast cancer and syringocystadenocarcinoma papilliferum. A 68-year-old man presented with a reddish 12-mm nodule on his left areola. No lymph node or distant metastases were observed. The patient was disease free 1 year and 9 months after the tumor was surgically resected but died of cerebral hemorrhage. Histopathological examination revealed a predominantly intradermal tumor with marked syringotropism, mimicking a component of mammary ductal carcinoma in situ. In addition, another tissue section displayed a cup-shaped papillated tumor with syringocystadenocarcinoma papilliferum-like features, which were also seen because of marked syringotropism. Diffuse immunoexpression of cytokeratin 7, cytokeratin 19, chromogranin A, synaptophysin, INSM1, estrogen receptor, carcinoembryonic antigen, epithelial membrane antigen, and GATA3 was observed in the tumor, but no BRAF immunoexpression was seen. The present case would help us to understand the histopathological variation and differential diagnosis of SCAND. The histopathological diagnosis of male breast cancer or syringocystadenocarcinoma papilliferum should be made by ruling out SCAND., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Digital papillary adenocarcinoma is a malignant adnexal tumor with a predilection for acral sites. Hidradenoma is a benign solid and cystic sweat gland neoplasm with focal ductal and glandular differentiation and good outcomes. Hidradenomas can occur at acral sites and show papillary structures; for this reason, they are included in the differential diagnosis of digital papillary adenocarcinoma, and immunohistochemistry is a valuable tool in this scenario. We described a case of a 43-year-old man with an epithelial tumor showing papillary structures in the intermediate phalanx of the fourth finger. There was diffuse positivity for p63 and negativity for S100 protein, suggesting that this tumor was an acral hidradenoma with papillary structures., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Moll gland is a modified tubular-shaped apocrine sweat gland, which is located on the margin of the eyelid. Moll glands are also known as ciliary glands. The function of these glands was not well known for a long time. However, based on the different studies, it was proved that Moll glands are active from birth and have local immunologic function producing immunoglobulin A. We present a case of Moll adenocarcinoma, a type of apocrine carcinoma, arising from the right upper eyelid of a 57-year-old man. Although Moll gland cysts are frequently seen, this type of adnexal malignancy is extremely uncommon. These tumors can have variable presentation and behavior from less invasive forms to highly malignant metastatic recurrent lesions., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: A 76-year-old female patient presented with a peculiar new exophytic-appearing, flesh-colored skin lesion on her left hallux. Owing to its atypical appearance, the neoplasm was biopsied. Histologic sections demonstrated numerous thickened, anastomosing cord-like structures composed of bland appearing adnexal keratinocytes attached to the epidermis and extending into the superficial dermis. Nearby areas exhibited papillomatosis, epidermal acanthosis, dense hyperparakeratosis, hypergranulosis, and superficial koilocytes, findings consistent with a verruca plantaris. A p16 stain was positive in many of the superficial epidermal keratinocytes. Human papillomavirus typing by in situ hybridization for the most common low-risk and high-risk types was also performed and was negative for these. We herein present an unusual case of a skin lesion which combines features of a poroma with a verruca plantaris. We further review what is known of the relationship between human papillomavirus and poroid neoplasms., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Background: Squamoid eccrine ductal carcinoma (SEDC) represents a subtype of eccrine carcinomas that are diagnostically challenging for both clinicians and dermatopathologists., Objective: To provide an updated review of SEDC and examine patient outcomes with different treatment modalities., Methods: A review of Ovid MEDLINE was performed to review the English language medical literature of SEDC., Results: A comprehensive review of clinical presentation, histologic findings, rates of lymphovascular and metastatic disease, treatment modalities and recurrence rates are reviewed., Limitations: There is a limitation on available data because of the rare incidence., Conclusions: SEDC is a rare adnexal neoplasm with a relatively high rate of local recurrence, lymphovascular invasion, perineural invasion, and metastases. Clinicians should be aware of this entity as close follow-up is essential to detect recurrence and metastatic disease. Mohs micrographic surgery seems to result in superior patient outcomes., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Eccrine porocarcinoma (EPC) is a rare sweat gland malignancy. Recognition of histologic features is challenging, and specific pathologic features correlate with risk of poor outcome. This single-center retrospective review and case series of 58 EPC cases from 2000 to 2016 elucidates epidemiologic and pathologic characteristics of EPC. Pathology slides from 52 cases were analyzed by a dermatopathologist for standardized variable characteristics, including previously determined high-risk features (HRF) associated with poor prognosis. The incidence of EPC increased over the study period with 3 times more cases diagnosed in the last 4 years than in the first 4 years. Most cases were in the elderly males (mean age 75 years), and 50% were located in the head and neck region. Although 38% of tumors exhibited one histologic HRF, only 10% exhibited more than one. Of the HRF, a greater tumor depth was associated with both increased age (P = 0.04) and clear cell differentiation (P = 0.02). This study elucidates epidemiologic and pathologic features of EPC and highlights how age and clear cell differentiation can be associated with greater tumor depth, although further research is needed to determine whether clear cell differentiation is associated with poor clinical outcome., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2021 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: A 91-year-old man presented with a tumor on the left temporal area, clinically suspicious of basal cell carcinoma. The histopathologic study showed a central solid-cystic tumor composed by 3 different types of cells (clear or finely granular cells, polygonal cells, and squamoid cells). It had a sclerotic stroma. At the periphery, another tumor composed by smaller interconnected nests was evident. Some nests were separated from the stroma by clefts. The stroma of this second tumor was highly cellular. There was a sharp delimitation between both tumors, with no transitional area. Immunochemistry demonstrated they are different tumor. A diagnosis of clear cell hidradenoma-basal cell carcinoma collision was performed. To the best of our knowledge, this is the first description of this challenging association., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Abstract: Papillary digital adenocarcinoma (PDA) is a rare eccrine tumor that is most often found on the digits. Few case reports have described PDAs located on atypical sites. It is now accepted that PDAs cannot be distinguished from benign adenomas based on histological features, and it is recommended to excise all of these lesions. Even with excision, recurrence and metastasis rates are high. Only limited genomic analyses have been performed to date, and no driver mutations have been identified. We report a case of a 63-year-old woman with a PDA on the right forearm. Biopsy showed moderate cytologic atypia and mitotic figures. Next-generation DNA sequencing of the tumor showed a BRAFV600E mutation and high tumor mutational burden (5.51 mutations/Mb). This mutation is known for its response to small molecular inhibitors of BRAF and Mitogen-activated protein kinase kinase. Such therapy may be a consideration should our patient develop recurrent unresectable disease., Competing Interests: The authors declare no conflicts of interest., (Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.)

Solid carcinoma, probably the solid variant of microcystic adnexal carcinoma, is an apocrine adnexal tumor first described in 1998. The authors report an additional new case of the tumor at an unusual localization. A 78-year-old man presented with an asymptomatic firm plaque on his right thigh that had been present for 15 years. A biopsy was taken, and then, the lesion was removed. A pathological study showed a huge number of islands made up of aggregations of neoplastic epithelial cells. The epithelial islands showed variable sizes and shapes at scanning magnification, arranged columns, cords, and strands at the basis of the tumor. The neoplastic cells were embedded within a fibrotic stroma. Ductal differentiation, cystic structures, and neurotropism were also observed. Immunohistochemically, the neoplastic cells expressed high-molecular-weight keratin (cytokeratin 5/6), broad-spectrum keratin (AE1/AE3), p40, and p63. No immunoreactivity was found for BerEP4, cytokeratin 7, cytokeratin 19, cytokeratin 20, chromogranin A, carcinoembryonic antigen, and S-100. The lesion was completely removed with slow-Mohs micrographic surgery. Two stages and previous debulking were necessary to obtain free margins. The second stage included the muscular fascia. The patient remains free of tumor after a year of follow-up. Solid microcystic adnexal carcinoma is a rare skin tumor that seems to occur more frequently in the scalp than in the face, but no area of the body can be excluded, as reported in our case. Differential diagnosis should include sclerosing and clear-cell basal cell carcinoma, clear-cell dermal duct tumor, or desmoplastic trichoepithelioma. Mohs micrographic surgery is the treatment of choice.

Endocrine mucin-producing sweat gland carcinoma (EMPSGC) and primary cutaneous mucinous carcinoma (PCMC) are both uncommon low-grade cutaneous adnexal tumors with predilection for the eyelids of elderly women. Their clinical appearance is nonspecific, typically presenting as a slowly growing poorly circumscribed papule, nodule, plaque, or swelling. Histological features of EMPSGC include a lobulated dermal neoplasm with bland cytology and an invasive mucinous component in up to half of the cases. PCMC exhibits tumor nests suspended in abundant pools of mucin with focal strands or nests of tumor cells infiltrating the dermis. Because of their rarity and banal cytological features, both entities pose a risk for misdiagnosis with other benign/malignant cutaneous adnexal neoplasms. Histomorphological features can suggest a diagnosis of EMPSGC or PCMC, but immunohistochemistry is necessary for confirmation. A review of the literature showed variable results of antigens present in EMPSGC, and many of the positive markers only show sparse or focal immunoreactivity of tumor cells. As a result, diffusely positive markers play a crucial role in identification of these tumors, particularly with initial superficial biopsies. We present 9 cases of EMPSGC and 5 cases of PCMC with strong and diffuse immunoreactivity to renal cell carcinoma antigen. This novel finding can be useful in the diagnosis of EMPSGC and PCMC in combination with other known positive markers to differentiate them from other cutaneous neoplasms. In addition, it provides further evidence that EMPSGC could be a precursor lesion to PCMC with both existing on a spectrum.

We present a case of cutaneous apocrine carcinoma arising in the axilla of a 71-year-old man. The tumor had a significant component of histiocytoid and signet-ring cells as well as in situ carcinoma within the apocrine glands. The cells expressed GATA3, gross cystic disease fluid protein 15, androgen receptor, and E-cadherin. Estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 were negative. Clinical correlation was required to rule out a metastasis from the breast or the gastrointestinal tract. Although most cutaneous apocrine carcinomas do not behave aggressively, our patient developed bone metastases and eventually died of his disease. It is debated whether histiocytoid and signet-ring cell cutaneous carcinomas should be classified as apocrine neoplasm. The presence of in situ carcinoma associated with this kind of tumor has been reported only once in the literature. This characteristic and the immunohistochemical profile are in favor of apocrine differentiation.

The authors report 11 cases of extramammary Paget disease (EMPD), all of which also demonstrated a combination of histological changes highly reminiscent of syringocystadenocarcinoma papilliferum in situ. In addition to the classical features of EMPD, characterized by the intraepidermal spread of individually dispersed neoplastic cells with ample cytoplasm, many of which contained mucin, there were areas of acanthosis with the substitution of spinous layer keratinocytes by neoplastic cells, whereas the native basal cell layer was intact. In addition to acanthosis (and sometimes papillomatosis), the dermal papillae showed a prominent infiltrate of plasma cells, completing the resemblance to syringocystadenocarcinoma papilliferum in situ; this similarity was further enhanced in 2 cases, which showed conspicuous gland formation. One additional case showed multifocal dermal proliferations compatible with eccrine syringofibroadenoma (syringofibroadenomatous hyperplasia). The changes described herein seem to be relatively rare in EMPD, and they can represent a diagnostic pitfall, as evidenced by 2 cases that were originally misinterpreted as syringocystadenocarcinoma papilliferum in situ. Clinically, these microscopic changes sometimes corresponded to nodular lesions, which were specifically noted to have a papillated erosive surface.

Aggressive digital papillary adenocarcinoma (ADPA) is a rare sweat gland neoplasm with a high recurrence rate and metastatic potential. In this study, the authors describe a case that originally appeared to benign spiradenoma, but took an ominous course eventually resulting in the diagnosis of ADPA. A 73-year-old woman developed a gradually growing nodule on the second toe of her left foot, which she had first noticed 4 years previously. An excisional biopsy was performed followed by histological examination. The authors initially considered the tumor to be a benign spiradenoma and did not perform reexcision. However, she experienced local recurrence 24 months later, and multiple pulmonary metastasis 31 months later. On histological examination, both the primary and locally recurrent tumors were found to be composed of discrete and well-circumscribed solid nodules, lacking cystic space. All tumors (the primary tumor, locally recurrent tumor, and lung metastases) presented with a pattern of fused back-to-back tubular structures and myoepithelial differentiation confirmed by immunohistochemical examination. On the basis of these findings, the authors finally diagnosed ADPA with multiple pulmonary metastases. The patient underwent chemotherapy, but died of disease 49 months later. This case highlights the importance of high clinical suspicion of ADPA when digital lesions present., Competing Interests: The authors declare no conflicts of interest.

Primary cutaneous sweat gland carcinomas (SGCs) are rare tumors that commonly involve axillae, have a high local recurrence rate, and rarely show sarcomatoid transformation. A 68-year-old man presented with rapid enlargement of a previously stable, asymptomatic pea-sized nodule in the left axilla. Initial excision (with positive surgical margins) at another institution showed characteristic histologic features of a high-grade osteosarcoma and molecular analysis using a 92-gene real-time quantitative reverse transcription-polymerase chain reaction assay confirmed a diagnosis of osteosarcoma with 96% certainty. Notably, the molecular assay demonstrated consistently high relative expression of pannexin 3 (PANX3), a gene involved in normal osteoblast differentiation which, when highly expressed, strongly predicts osteosarcoma per the assay's algorithm. However, on further histologic review, the tumor also contained focal cystic areas, nests, and ducts composed of malignant epithelial cells reminiscent of SGC; these areas directly transitioned into the osteosarcomatous component and were strongly positive for pancytokeratin, CK7, and p63. Within 2 weeks, the lesion recurred and grew rapidly, prompting complete resection, histologic sections of which showed high-grade osteosarcoma without residual epithelial elements. This is the fifth report, to our knowledge, of osteosarcomatous transformation in a SGC, and the only report to date including molecular data. This case demonstrates that osteosarcoma arising from a SGC has a similar molecular profile to de novo primary osteosarcoma of bone. It also emphasizes the importance of histopathologic findings as the established diagnostic gold standard and the need to interpret molecular results within the clinical context.

Adenomyoepithelioma (AME) is a biphasic neoplasm of epithelial and myoepithelial cells. It is most commonly found in the breast, although rare cases have been reported from the lung, salivary glands, and skin. There are 5 well-documented cases of cutaneous AME in the literature. We report a new case of cutaneous AME. Our case was commingled with apocrine hidrocystoma. This is the first report of cutaneous AME in a male patient and the first to describe SOX10 immunostaining in cutaneous AME. We review the literature on cutaneous AME and note the greater than chance colocalization with other adnexal tumors. We speculate that AME may represent localized overgrowth of myoepithelial cells within a pre-existent sweat gland tumor. Histopathologists should be aware of the potential of SOX10-positive myoepithelial neoplasms to mimic nodular melanocytic proliferations.

Spiradenocarcinoma is a very rare malignant tumor. In situ adenocarcinoma has recently been observed and defined by the preservation of a peripheral myoepithelial cell layer. The pathway for this phenomenon has been hypothesized to involve a sequence of adenomatous changes followed by atypical adenomatous changes, adenocarcinoma in situ, and invasive adenocarcinoma. However, there are no clearly defined morphological distinctions between atypical adenomatous changes and adenocarcinoma in situ. The authors present a case of spiradenocarcinoma in a preexisting spiradenoma in the left inguinal area of a 71-year-old woman. Adenomatous changes, atypical adenomatous changes, adenocarcinoma in situ, and invasive adenocarcinoma were found within the same lesion. The majority of the malignant component was an in situ adenocarcinoma. Although a loss of the myoepithelial cell layer and coalescing, irregular, glandular nests were present in several discrete foci, this case did not show infiltrative growth beyond the fibrous connective tissue. The authors speculate that this case represents a very early invasive spiradenocarcinoma lesion. We present this case to discuss the histological and/or immunohistochemical criteria of atypical adenomatous changes and to discuss the optimal treatment in cases with a disparity between the preservation of the whole architecture and the loss of the myoepithelial cell layer, which may be associated with favorable biological behavior.

The progressive calcification and fragmentation of elastic fibers, primarily affecting the skin, are histopathologic features typically associated with pseudoxanthoma elasticum (PXE), pseudo-pseudo PXE, or even acquired PXE. We present a case of a 65-year-old woman, with a known history of breast carcinoma, status after wide excision (T1N0Mx) in 2010, who presented with a 0.6 × 0.5-cm, nontender pink nodule in the right inferior axilla of 1 week duration on the same side as her mastectomy. Histopathologically, the lesion revealed a circumscribed, nonencapsulated bland dermal tumor with poroid and clear cells and foci of ductal differentiation-features diagnostic for hidradenoma. Of note, immediately adjacent to the hidradenoma, the specimen also exhibited short, frayed elastic tissue fibers (positive for EVG and Von Kossa stains)-features reminiscent of PXE. With this case, we expand the spectrum of reaction patterns observed in the skin to include a PXE-like change, a reaction pattern that, to the best of our knowledge, has not been previously reported in association with a benign cutaneous tumor.

Microcystic adnexal carcinoma (MAC) is an uncommon, locally aggressive, malignant cutaneous tumor with pilar and eccrine differentiation. Mohs micrographic surgery is the treatment of choice for this condition, but specific histological findings can complicate MAC removal and leave doubt as to whether the tumor has been completely removed. Here we describe the clinical and pathological characteristics of a case in which a patient with an MAC underwent multiple reexcisions because of the presence of benign subclinical syringomatous proliferations adjacent to the primary lesion. Our case raises awareness of syringomatous proliferation, a benign process histologically similar but behaviorally distinct from a primary MAC. This experience highlights the importance of continued communication between dermatopathologists and dermatologic surgeons in providing quality patient care.

Malignant chondroid syringoma is a very rare type of malignant sweat gland tumor. Diagnosis is based on pathologic features but is complicated by the low frequency of this tumor. The authors report a new case of malignant chondroid syringoma, initially misdiagnosed as basal cell carcinoma, that exhibited very aggressive local behavior and was located on the face, a rare site for this tumor. The authors describe its histopathologic appearance and highlight the importance of including adenoid cystic carcinoma in the differential diagnosis.

Endocrine mucin-producing sweat gland carcinoma (EMPSGC) is a rare low-grade sweat gland carcinoma with a strong predilection to the eyelid region. It is histologically analogous to endocrine ductal carcinoma/solid papillary carcinoma of the breast and is characterized by a multinodular solid cystic mucinous tumor with immunoreactivity to neuroendocrine markers. Only 20 cases of this unusual tumor have been reported. We present the clinical and histopathologic findings of 2 new cases of EMPSGC and review the relevant literature. The histological differential diagnosis is discussed and attention drawn to the role of immunohistochemistry in clarifying the nosological position of EMPSGC within the spectrum of cutaneous mucinous neoplasms.

Apocrine carcinoma (AC) is an extremely rare skin appendage tumor, which is located at lower dermal and subcutaneous tissue. We report a case of an anal AC arising from an apocrine adenoma in the anal region, which is only the second case reported in this region. A 71-year-old male presented to clinic with soreness in the anal region for 6 weeks. An excisional biopsy was performed. Histologically, the lesion was poorly circumscribed, infiltrative, and was composed of small to medium sized glands extending to the surgical margins. There were centrally dilated large glands with duct-like openings into the mucosal surface. The larger central glands contain periodic acid-Schiff-positive eosinophilic acellular secretions. At the periphery, there were smaller glands with significant cytologic atypia and numerous mitoses. A diagnosis of AC was made making it the second case report of this very rare malignancy in this region. Although ACs usually do not have a fatal outcome, there have been case reports of distant metastases and even death from this disease, making histologic distinction of this malignancy from a benign apocrine adenoma important. Wide local excision is typically the treatment of choice, although Mohs micrographic surgery has also been used with similar success.

Apocrine nevus is a rare tumor composed of increased mature apocrine glands and ductal structures within a fibrous stroma, located predominantly in the reticular dermis. They have been reported in association with apocrine carcinoma, extramammary Paget disease, and syringocystadenoma papilliferum; less commonly a pure apocrine nevus is identified, unassociated with another apocrine proliferation. Clinically apocrine nevi may appear as solitary or multiple nodules or plaques on the scalp, presternal skin, though they are seen most commonly in the axillae. We describe 4 cases of pure apocrine nevus, all of which appeared clinically as painless or mildly tender skin-colored axillary masses, 2 of which were bilateral. In each case, the lesions appeared in adulthood, and patients denied knowledge of congenital or childhood presence. Patients denied pruritis, discharge, bleeding, or antecedent trauma. Grossly, the specimens consisted of subcutaneous, multicystic ill-defined nodules. Biopsy showed prominent apocrine glands composed of irregularly columnar luminal cells with eosinophilic cytoplasm arranged in a somewhat organoid pattern filling the reticular dermis and extending into the subcutaneous adipose tissue. The glandular luminal cells displayed decapitation secretion. There was a paucity of pilosebaceous units. In one case, the overlying epidermis was papillomatous. The deepest portion of one specimen had lactational change simulating a lactational adenoma. No atypia was seen in either the glandular structures or the stroma. The adjacent sebaceous and eccrine structures were normal. The histologic features and immunohistochemical profile in relation to other apocrine lesions will be reviewed.

Cutaneous pseudocarcinomatous hyperplasia is a benign proliferation that can be associated with many nontumoral and tumoral conditions. In the literature, squamous proliferations of different types have been associated with several types of adnexal adenomas. However, we found no reported case of association of hidradenoma papilliferum with pseudocarcinomatous hyperplasia. We had the opportunity of studying this type of an association in a 38-year-old man. The hidradenoma was located deep in the corion of the biopsy and the uppermost squamous epithelium showed a pseudocarcinomatous hyperplasia that focally contacted with the hidradenoma. No atypia was noted in the squamous proliferation. E-cadherin was diffusely expressed by the squamous nests, whereas p53 and Ki-67 were restricted to the basal layer. Cyclin D-1 was expressed in the parabasal layer. Immunohistochemistry of the squamous proliferation was negative for human papillomavirus.

Hidradenoma papilliferum of the anogenital region was previously believed to originate from apocrine glands but has recently been accepted as originating from anogenital mammary-like glands. We describe a case of hidradenoma papilliferum with mixed features of syringocystadenoma papilliferum and mammary-like glands from the left labia majora of a 25-year-old woman. Histopathologically, the lesion showed an epithelial lining with apocrine secretion, and like syringocystadenoma papilliferum, the lesion extended from the epithelium as invaginations into the dermis. Adjacent to this lesion were ductal and glandular structures resembling normal mammary tissue. This review of the literature highlights the heterogeneity and complexity of lesions arising from anogenital mammary-like glands, and this case serves as further documentation of the association between anogenital mammary-like glands and hidradenoma papilliferum.

We recently observed atypical adenomatous metaplasia of eccrine glands in an excisional biopsy of squamous cell carcinoma (SCC). This led us to this study in an effort to ascertain whether this reaction pattern is common to all excisional biopsies and, depending on its presence in association with residual tumor, whether it is lineage specific. We performed a retrospective review of 201 excisional biopsies and noted that adenomatous metaplasia was present in 35 of 201 (17%) of the cases, of which 19 had residual tumor. Adenomatous metaplasia seemed to be more frequent in epithelial neoplasms such as basal cell carcinomas 15 of 94 (16%) and SCCs 13 of 61 (21%) although only (3 of 41) 7% of nevomelanocytic proliferations exhibited this change. Residual tumor was noted in association with adenomatous metaplasia, in 11 of 15 cases (73%) in the basal cell carcinoma subgroup, in 8 of 13 cases (62%) in the SCC subgroup, and in none from the nevomelanocytic subgroup. Comparing frequencies of adenomatous metaplasia across groups, only SCC specimens with residual tumor demonstrated a statistically significant increase compared with nevomelanocytic neoplasm (35% vs. 7%, P = 0.01). Findings from the current study expand the spectrum of metaplastic change involving eccrine glands to include adenomatous metaplasia. Given that it seems to be more common to epithelial malignancies, it seems reasonable to posit that this reaction pattern is the consequence of hitherto undefined proteins induced by epithelial tumor cells resulting in exuberant stimulation of eccrine glands, although immunohistochemical and molecular studies are required to define the precise cause.

Eccrine ductal carcinoma is a rare adnexal tumor. Squamoid eccrine ductal carcinoma (SEDC) represents an exceptionally rare variant with only 6 cases reported to date. This neoplasm is deeply infiltrative and may provide a diagnostic challenge in superficial shave biopsies of skin. We present a case of SEDC in an immunocompromised patient, who, after an initial shave biopsy for diagnostic purposes, underwent a complete excision of his tumor by Mohs micrographic surgery. A combined histologic and immunohistochemical approach is necessary to identify and confirm the unique characteristics of SEDC. Because this cancer is very rare and little is known about its biologic behavior, optimal diagnostic and treatment guidelines need to be developed.

Syringoma exclusively located to the penis is an extraordinary rare dermatological condition, and only 6 patients with syringoma exclusively located to the penis have been published previously. Light microscopical examination of routine hematoxylin and eosin-stained sections from punch biopsies with adequate depth from 2 patients was performed. Classical syringoma was diagnosed. The lesions occurred in an eruptive fashion in both patients on the dorsal and lateral aspects of the penis shaft. There was a variation in clinical appearances ranging from yellow-white papules, a few millimeter in size to, in one of the patients, formation of several slightly elevated plaques, 10 mm in size, with a brownish-red color. We describe clinicopathological features of 2 patients with syringoma exclusively located to the penis. These are compared with all the previously published cases. Clinical and histopathological differential diagnoses are discussed, and a literature review is presented.

Apocrine fibroadenoma (AFA), considered a counterpart of fibroadenoma of breast, is a rare cutaneous apocrine neoplasm occurring almost exclusively in women. We describe a 75-year-old man who presented with a red dome-shaped papule near the nasal bridge. The tumor was composed of numerous tubular, cystic, and partially branching lumina and struts of epithelial cells oriented perpendicular to the skin surface, with which it connected through infundibula. The epithelial strands were embedded in fibrocollagenous stroma. These histopathological features are consistent with AFA. The cytokeratin profiles of our case were similar to those of apocrine or eccrine neoplasms. Progesterone and estrogen receptors (PR/ER) were not expressed. The stroma cells were stained strongly positive for vimentin, but nonreactive for alpha-smooth muscle actin, S-100 protein, or glial fibrillary acidic protein. To the best of our knowledge, this is the first report of facial AFA in man. Different from a more common anogenital AFA, this neoplasm might represent a second type of AFA with unique histopathologic and immunopathological features.

Basal cell carcinoma (BCC) has many histologic variants. These variants may show differentiation toward benign and malignant tumors of cutaneous appendages, especially hair follicles. Herein we describe a lesion that was clinically thought to be a BCC, but a superficial biopsy showed histologic features suggestive of an apocrine hidrocystoma. Because of some cytologic atypia, complete excision was recommended. The excision specimen revealed a cystic BCC. The importance of examining the entire neoplasm before reaching a final pathologic diagnosis is emphasized.

Malignant eccrine spiradenoma (MES) is a very rare tumor. Tumors can be low grade or high grade. There are nine cases in the literature with systemic metastases. Of these, only one was low grade; the others had obvious features of high-grade malignancy such as pleomorphism, increased mitoses, and abnormal mitoses. Low grade MESs are more difficult to diagnose and are said to have a better prognosis. We report an additional case of low-grade MES with systemic metastases. It had a monotonous appearance with few mitotic figures and minimal pleomorphism. Vascular invasion was seen in both cases of low-grade MES and may be an important prognostic feature.

Syringoid eccrine carcinoma is an extremely rare cutaneous malignant tumor, thought to be derived from eccrine sweat apparatus. We report a case of syringoid eccrine carcinoma occurring on the scalp of a 66-year-old woman and analyzed its cytokeratin expression immunohistochemically to clarify its histogenesis. The tumor consisted mainly of numerous small cords and nests extending from the reticular dermis to the subcutaneous tissue, which formed luminal or tubular structures mimicking the nests of syringoma. Immunohistochemical analysis revealed that most tumor cells expressed simple epithelial cytokeratins (CKs 7, 8, 18, 19) suggesting their sweat secretory differentiation, and that a small number of tumor cells showed an expression of stratified epithelial cytokeratins (CKs 5, 14) suggesting their ductal differentiation. We believe that the syringoid eccrine carcinoma of our case may differentiate mainly toward the sweat secretory cells rather than toward the dermal ductal cells.

We present the case of a 9-year-old girl with a perianal skin tag. This asymptomatic lesion was removed for cosmetic reasons and demonstrated a polypoid lesion with a slightly acanthotic epidermis. The dermis was filled with mature-appearing eccrine ducts and glands but with no other cutaneous appendages, adipocytes, or abnormal vascularity. We believe this to represent a polypoid eccrine nevus and that its presentation is unique.

Poromas are benign neoplasms composed of poroid and cuticular cells. Four histopathologic variants of poromas are accepted, according to the architectural features of the neoplasm: hidroacanthoma simplex or intraepidermal poroma; eccrine poroma, which is a poroma connected to the epidermis that extends to superficial dermis; dermal duct tumor, which develops when the neoplasm is composed of small, solid aggregations of poroid and cuticular cells confined to the dermis with little or no connection with the epidermis; and poroid hidradenoma, which is a solid-cystic, dermal poroma. The malignant counterpart of hidroacanthoma simplex is named malignant hidroacanthoma simplex or porocarcinoma in situ. This report describes an example of clear-cell malignant hidroacanthoma simplex, a cytologic variant of porocarcinoma in situ, which, to our knowledge, has not been previously reported. In contrast with other clear-cell neoplasms, a relation with diabetes mellitus could not be clearly established in this case.

We report a case of an aggressive digital papillary adenocarcinoma (ADPA) on the right thumb of a 48-year-old white man. Histologic evaluation of the initial biopsy demonstrated features consistent with those proposed for aggressive digital papillary adenoma; however, re-excision of the remaining lesion revealed histologic features consistent with aggressive digital papillary adenocarcinoma. These tumors have a high rate of local recurrence and can metastasize, occasionally resulting in mortality. Our case demonstrates that even if the histologic criteria of aggressive digital papillary adenocarcinoma are met, the lesion may still represent an aggressive digital papillary adenocarcinoma (ADPAca). In agreement with a recent study by Duke et al., this case supports the idea that aggressive digital papillary lesions should be classified as aggressive digital papillary adenocarcinoma.

Malignant eccrine spiradenoma is a very rare tumor. The clinicopathologic features of 12 cases are reported herein. Six patients were men, six were women, and the average patient age was 62 years. Seven tumors were located on the trunk, three on the extremities, and two in the head and neck region. All tumors were large (average size-7.5 cm). Lesions had been present from 7 months to 30 years before surgical removal. In all cases, continuity between benign eccrine spiradenoma and areas with malignant change was observed. Malignancy was evidenced by increased mitotic rate, necrosis, nuclear atypia, pleomorphism, and hyperchromasia, loss of nested and trabecular growth patterns, and absence of a dual cell population. In most cases (8 of 12), the malignant component comprised the bulk of the lesion. Two distinctive histologic patterns were observed. Five of 12 tumors exhibited abrupt transition between a benign eccrine spiradenoma and a high-grade carcinoma component. The others lacked a clear-cut transition between benign and malignant components and were diagnostically challenging. Diagnosis in such cases was established based on the loss of two cell populations, increased nuclear to cytoplasmic ratio, hyperchromasia, and marked mitotic activity. Two tumors showed focal squamous differentiation. Five of seven patients on whom there was follow-up information were free of disease (average duration of follow-up = 3.4 years). One patient developed metastases to local lymph nodes 5 years after the primary tumor was resected. This patient had no evidence of disease 16 months after resection of her lymph node metastases.

Primary mucinous carcinomas of the skin are very rare. To date, 120 cases have been described in the literature. This tumor is a histologic subtype of sweat gland carcinoma. Because of the histopathologic appearance, primary mucinous carcinoma of the skin can be mistaken for metastasis from extracutaneous sites. We report on the cases of two elderly women with mucinous carcinomas arising in the scalp. Immunohistochemical staining of both tumors was positive for low-molecular-weight cytokeratin and epithelial membrane antigen. Carcinoembryonic antigen was positive in Case 2. Neuroendocrine features represented by neuron-enolase-specific positivity were also observed in both cases, and Grimelius and chromogranin A positivity were observed in Case 2. In both cases, there was strong positivity for estrogen receptor and progesterone receptor. Image analysis cytometry showed a diploid DNA content with a low rate of proliferative cells and negativity for p53 and c-erbB-2 proteins in agreement with the low aggressiveness of these neoplasms.

p53 protein is a nuclear 53-kDa phosphoprotein that acts as a suppressor protein. There are several studies on the expression of p53 in skin tumors, but few deal with adnexal malignant tumors because of their rarity. We performed immunohistochemistry for the detection of p53 and Ki-67 in two cases of malignant spiradenomas and six cases of spiradenomas retrieved from our files. In our cases, p53 was expressed only in the malignant areas of the lesions, whereas the benign areas of the spiradenocarcinomas and all the spiradenomas were negative (nuclear positivity <10%). These results seem to support the idea that p53 is implicated in the malignant transformation of adnexal tumors.