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Fibrous histiocytoma (FH) or dermatofibroma is a common cutaneous lesion mostly seen in adults and rare in the first two years of life. Two hundred sixty-seven patients younger than 18 years with a diagnosis of FH or dermatomyofibroma, a lesion with morphologic overlap with FH, were identified from the files of a single institution, with only 13 (4.8%) occurring in patients younger than 5 years. Ten patients had either underlying neurologic, autoimmune, or metabolic disorders or a family history of autoimmune conditions. Histologic review of hematoxylin and eosin staining and immunostaining on 75 FHs and dermatomyofibroma in 70 patients showed the following results: 33 classic FHs, 8 classic FHs characterized by a peculiar retiform morphology with thin fascicles of elongated cells forming a network reminiscent of the eruptive variant of FH, 19 deep/cellular variants, 5 aneurysmal variants, 3 lipidized variants (including two lesions in a patient affected by mucopolysaccharidosis IV), 3 dermatomyofibromas, and 4 isolated cases of hemosiderotic, granular cell atypical, and epithelioid FH. Immunostaining for factor XIIIa highlighted a dense network of dendritic cells in FH, which was significantly reduced in the FH with retiform morphology. Smooth muscle actin staining was positive in a high percentage of FHs (85.3%). The current series demonstrates that FH in children may show unique clinical and morphologic features. The retiform pattern with decreased dendritic cells found in congenital lesions and in two older patients with lesions in two locations might have a different pathogenesis, probably related to an altered immune response in very young patients., (Copyright © 2020 Elsevier Inc. All rights reserved.)

In the 2018 World Health Organization Classification of Skin Tumors, a wide range of predominantly benign mesenchymal neoplasms are included in the fibroblastic, myofibroblastic, and "fibrohistiocytic" categories. By far the most common of these tumors is dermatofibroma (fibrous histiocytoma). There are many histologic variants of dermatofibroma, some of which (cellular, aneurysmal, and atypical) are associated with a higher risk of local recurrence; these variants may be mistaken for more aggressive tumor types, including sarcomas. Furthermore, distinguishing among the fibrous and "fibrohistiocytic" tumors can be a diagnostic challenge, given their sometimes-similar histologic appearances and confusing nomenclature. Immunohistochemistry and molecular genetic assays play a relatively limited role in the diagnosis of these tumor types, with notable exceptions (i.e., epithelioid fibrous histiocytoma and dermatofibrosarcoma protuberans). Proper recognition of dermatofibrosarcoma protuberans is critical, since this tumor type is associated with locally aggressive behavior; transformation to the fibrosarcomatous variant brings metastatic potential. In recent years, understanding of the molecular pathogenetic basis for cutaneous mesenchymal neoplasms has increased dramatically, with the discovery of gene rearrangements in some of these tumor types. In this review, the histologic features of the most common fibrous and "fibrohistiocytic" cutaneous mesenchymal neoplasms will be discussed, as well as recently identified molecular genetic alterations.

Epithelioid fibrous histiocytoma (EFH) is a rare lesion believed to arise from dermal microvascular unit fibroblasts and dendritic histiocytes. EFH has long been considered a morphologic variant of benign fibrous histiocytoma (dermatofibroma), with prominent epithelioid cytomorphology that can mimic both vascular and melanocytic neoplasms. The molecular basis for the relationship between EFH and benign fibrous histiocytoma has remained largely unknown, with some authors suggesting that EFH represents an entity that is biologically distinct from benign fibrous histiocytoma. Recent molecular studies have identified the presence of recurrent anaplastic lymphoma kinase (ALK) gene rearrangements, a phenomenon that has not been described in benign fibrous histiocytoma. These new molecular findings highlight the uniqueness of this rare tumor and may prove useful as a diagnostic tool for differentiation from other histologic mimics.

Langerhans cell (LC) histiocytoma is a neonatal tumor that often consists of a single, ulcerated nodule. Systemic involvement is rare, and LC histiocytoma is considered to be a variant of congenital, self-healing LC histiocytosis (also referred to as Hashimoto-Pritzker disease). In view of its low prevalence, LC histiocytoma is not always diagnosed in a clinical examination and requires histological confirmation. Furthermore, the histological and molecular features of LC histiocytoma have not been well characterized. Here, we report on 6 cases of this rare disease and review the corresponding literature. LC histiocytoma differs from classical self-healing LC histiocytosis with regard to the pathological features; we found that LC histiocytoma was associated with massive infiltration by histiocytes of various sizes and shapes (although often large) throughout the dermis and the superficial subcutis. Epidermotropism was rare, mitotic figures were not inconspicuous, and necrotic or calcified areas were often present. Immunohistochemical assessment revealed a mixture of different types of histiocytes (with CD1a CD207, CD1a CD207, and CD1a CD207 CD163 cells). Genetic testing was performed in 5 cases; it revealed a BRAF mutation (p.V600E and p.485_490delinsF) in 2 cases, a HRAS mutation (p.T58I) in 1 case, a combination of 2 PTEN mutations in another case (p.I224M and p. R234W), and no mutations in the fifth case. All the lesions regressed spontaneously, and none recurred during follow-up.

Atypical fibroxanthoma is considered to be a low-grade sarcoma, characterized by a proliferation of bizarre spindled cells. A case of a rare variant of this tumor, a clear-cell atypical fibroxanthoma, presenting with rapid growth on a 63-year-old female, is reported. The differential diagnosis of a clear cell proliferation and a review of the immunohistochemistry markers used in the diagnosis of atypical fibroxanthoma are discussed. In particular, the usefulness of markers such as CD10, procollagen 1, CD68, CD163, CD99, and S100A6, and the importance of negative markers such as S100, cytokeratin, and desmin are emphasized. Furthermore, the development of a keratoacanthoma at the site of previous Mohs surgery is recounted.

Alterations in dermal collagen are noted in dermatofibroma, dermatofibrosarcoma protuberans, morphea, lichen sclerosus et atrophicus, hypertrophic scars, and keloids. The authors sought to determine whether variations in birefringence of collagen by polarized microscopy could be of help in diagnosing such conditions. Representative hematoxylin and eosin sections of 400 cases, including dermatofibroma, dermatofibrosarcoma protuberans, hypertrophic scars, keloid, morphea, and lichen sclerosus, were examined under polarized microscopy. Distinct patterns of birefringence of collagen for each disease were noted under polarized microscopy. This study highlights the use of polarized microscopy as adjunctive tool in differentiating different diseases with collagen alteration.

Sclerosing angiomatoid nodular transformation (SANT) is a relatively new entity in the spleen, which usually presents in the form of single nodule. Only 5 multifocal SANT cases have been reported in English literature. The present case is the first report of a 38-years-old male patient with SANT in the form of multiple nodules, who has been cured via laparoscope. In comparison to solitary SANT, multifocal SANT occurs more likely in males than females and association with malignant neoplasm has not been described yet. Multifocal SANT as well as solitary SANT show some relationships with IgG4-related sclerosing disease.

Dermatofibroma is a common benign fibrohistiocytic tumor with many clinicopathological variants. Myxoid dermatofibroma is one of these variants, which is characterized by marked stromal mucin deposition. This report presents a case of myxoid dermatofibroma on a great toe that had been slowly growing for two years. Histopathologically, the relatively well-circumscribed dermal tumor was separated from the epidermis by a small grenz zone. The tumor tissue consisted of oval to spindle-shaped cells with well-defined cell borders and spindly condensed nuclei. No cytologic atypia or mitotic figures were found. Although most of the tumor cells were embedded in a prominently myxoid stroma, typical features of classic dermatofibroma including a storiform growth pattern and more densely packed collagen were observed at the periphery. Immunohistochemically, the tumor cells showed positive staining for CD68 and CD99, and negative staining for CD34 and S-100. Histopathological differential diagnoses of myxoid dermatofibroma include soft tissue neoplasms with myxoid tumor stroma, such as superficial acral fibromyxoma, cellular digital fibroma, superficial angiomyxoma, myxoid dermatofibrosarcoma protuberans and low-grade fibromyxoid sarcoma. Immunohistochemical staining can be useful in the differential diagnosis of these tumors. This case highlights the challenges encountered in the histopathological interpretation of myxoid dermatofibroma. Pathologists should keep in mind the diagnosis of myxoid dermatofibroma when dealing with myxoid neoplastic lesions arising on acral sites.

Sclerosing angiomatoid nodular transformation of the spleen (SANT) is a benign, extremely rare vascular lesion of the spleen with unknown pathogenesis. SANT is often discovered incidentally, and can sometimes be found in patients with a history of cancer. Based on absent definitive radiological signs and varying growth patterns, distinction from malignant processes such as metastasis can be very difficult. Therefore, surgical resection of the spleen is indicated in most cases of patients with history of cancer. We report a case of a bifocal manifestation of SANT in the spleen in a patient with history of colon cancer and newly-diagnosed metachronous liver metastases.

Objectives: While useful in diagnosing angiosarcomas, CD31 can also highlight histiocytes within soft tissue tumors and lead to errors in diagnosis. We sought to determine how often CD31 highlights cutaneous histiocytomas and histiocytoma mimics., Methods: We examined eight epithelioid cell histiocytomas (ECHs), 12 xanthogranulomas (XGs), nine cases of Langerhans cell histiocytosis (LCH), eight reticulohistiocytomas, 11 xanthomas, 29 atypical fibroxanthomas, nine granular cell tumors, four cases of angiolymphoid hyperplasia with eosinophilia, nine intradermal Spitz nevi, and nine angiosarcomas with antibodies directed against CD31, CD34, CD163, and factor VIII., Results: CD31 marked cells in three of 12 XGs, four of nine cases of LCH, one of eight reticulohistiocytomas, one of 11 xanthomas, 10 of 29 atypical fibroxanthomas, four of four cases of angiolymphoid hyperplasia with eosinophilia, nine of nine angiosarcomas, zero of nine granular cell tumors, and zero of eight ECHs. CD34 and factor VIII were negative in all nonvascular cases., Conclusions: Our results indicate that CD31 can mark lesional cells and imitate vascular tumors in cutaneous histiocytomas and histiocytoma mimics, an error that can be avoided by using a panel of antibodies., (Copyright© by the American Society for Clinical Pathology.)

Multinucleate cell angiohistiocytoma (MCA) is a benign fibrohistiocytic and vascular proliferation usually located on the extremities. It may be underdiagnosed owing to lack of recognition by clinicians and pathologists. We report a 48-year-old man with asymptomatic grouped reddish papules on the dorsum of his right hand for 8 years. Histopathological and immunohistochemical examinations revealed features of MCA with a fibrohistiocytic cell infiltrate in the dermis and multinucleate cells in the stroma. Recently, the dermoscopy aspects of MCA have been described. We add another observation of this useful tool and correlate it with clinical evolution.

Previously unrecognized but clinicopathologically (and often molecularly) distinct types of soft tissue tumor continue to be characterized, allowing wider recognition, more consistent application of diagnostic criteria, more reliable prediction of tumor behavior and enhancement of existing classification schemes. Examples of such 'entities' that have become much better understood over the past decade or so include deep 'benign' fibrous histiocytoma, hemosiderotic fibrolipomatous tumor, PEComa, spindle cell liposarcoma, myoepithelial tumors of soft tissue and spindle cell/sclerosing rhabdomyosarcoma. These tumor types, as well as the insights which they have engendered, are briefly reviewed here.

Dermatofibromas (DFs) are common benign fibrohistiocytic lesions, mostly affecting young adults. Many types of DF have been described, depending on architectural, cellular, and stromal peculiarities. Recently, a peculiar type of benign cutaneous tumor showing hemosiderotic DF-like stroma and apocrine glands has been described. We report 2 additional cases of DF without hemosiderotic changes showing entrapped apocrine glandular structures. We speculate about the origin of the glandular component and propose the term adenodermatofibroma for this type of lesions.

Orbital lesions include a broad spectrum of tumors, vascular abnormalities, and inflammatory conditions. High-resolution imaging has become an invaluable tool toward formulating an accurate diagnosis, and facilitates proper counseling regarding appropriate interventions. Imaging may guide whether partial excision to minimize damage to orbital structures, or en bloc removal to prevent potential recurrence, as seen in mesenchymal tumors, is indicated., Recently, dynamic contrast-enhanced magnetic resonance angiography (MRA) has demonstrated use in helping differentiate orbital vascular lesions. This imaging modality uses rapid MRI acquisition to provide noninvasive, dynamic flow information with high spatial resolution. However, even with modern imaging, reaching a diagnosis prior to histopathological analysis can be challenging. We present a case of orbital fibrous histiocytoma that appeared nearly identical to cavernous hemangioma on dynamic contrast-enhanced MRA.

Purpose: Atypical fibroxanthoma is a cutaneous dermal malignancy that presents on the sun-damaged skin of elderly people. It requires a definitive diagnosis, from a high-grade sarcoma to a nonmesenchymal neoplasm. The recommended treatment protocol differs from similar histologically related tumors; thus, a diagnosis of atypical fibroxanthoma should fulfill strict histologic and immunohistochemical stain criteria. The use of these standards will exclude other skin malignancies, including malignant fibrous histiocytoma, angiosarcoma, malignant melanoma, and squamous cell carcinoma. This study was performed with the aim of identifying key immunostains to develop diagnostic criteria., Materials and Methods: Forty-two cases were studied retrospectively over a 10-year period using a panel of immunostains., Results: The average age at presentation was 78 years, with a male predominance. The scalp was found to be the most common site of occurrence, although other investigators have found the forehead, cheeks, nose, and ears as the prevailing sites of presentation., Conclusions: An extensive panel of immunohistochemical stains can be used to prove a diagnosis of atypical fibroxanthoma., (Copyright © 2012 American Association of Oral and Maxillofacial Surgeons. Published by Elsevier Inc. All rights reserved.)

A heterogeneous group of benign fibrohistiocytic lesions has been assembled under the umbrella term, dermatofibroma. These lesions share a morphology of bland spindled cells encompassed by and intercalating through thick dermal collagen; unique variants have been described based on secondary histologic features, some of which include aneurysmal, myxoid, lipidized, signet ring, angiomatous, and keloidal. Here, we present a distinct dermatofibroma variant henceforth known as collapsing angiokeloidal dermatofibroma identified in 2 patients with slowly growing nodules of the buttock and the arm. Microscopically, the lesions have a characteristic dermatofibroma appearance but are accompanied by unusual diffuse small caliber vessels whose walls are collapsed by a thick, eosinophilic, keloid-like substance. The eosinophilic material resembles the adjacent dermal collagen; however, it does not stain for type-4 collagen or type-1 procollagen, amyloid, or glycogen. Although the exact composition of the keloidal material remains ambiguous, the architectural novelty of collapsing angiokeloidal dermatofibroma serves to further expand the morphologic spectrum of benign fibrous histiocytomas, although highlighting the difficulty in distinguishing between it and similar lesions.

Background: Biodegradable interference screws in anterior cruciate ligament (ACL) reconstruction have gained popularity because of their similar or superior fixation strength in comparison to metallic interference screws and because they do not cause imaging artifacts and do not need to be removed., Case Description: We report the case of a 23-year-old man who presented with slowly progressive firm swelling of 2 months' duration at the site of the tibial tunnel 3 years after ACL reconstruction using a biodegradable interference screw. After curettage and débridement, the material was sent for histopathologic examination, which was reported as a fibroxanthoma., Literature Review: Reported complications are osteolysis around the screw, allergic reaction, sterile abscess formation, ganglion cyst formation, and intraarticular migration. A fibroxanthoma consists of fibroblasts and mononuclear or multinucleated cells with large lipid-filled histiocytes (foam cells). The cells are negative for S-100 and keratin and positive for anti-human macrophage marker HAM-56., Purposes and Clinical Relevance: Use of biodegradable screws is associated with high healing rates and low complication rates; however, awareness of their potential complications may help in early recognition and prevention of associated morbidity.

CD163, a hemoglobin scavenger receptor, is expressed in monocytes and macrophages. Recent work has shown that this marker is specific for neoplasms of histiocytic differentiation. Our aim was to test the ability of CD163 to separate cutaneous histiocytomas from their morphologic mimics. We tested the expression of CD163 in 78 cases, including 19 xanthogranulomas, 16 atypical fibroxanthomas, 6 reticulohistiocytomas, 8 epithelioid cell histiocytomas, 9 cases of Langerhans cell histiocytosis, 10 xanthomas, and 10 intradermal Spitz nevi. CD163 expression was seen in all xanthogranulomas and reticulohistiocytomas, 4 epithelioid cell histiocytomas, 2 cases of Langerhans cell histiocytosis, and 8 xanthomas but was absent in atypical fibroxanthomas and Spitz nevi. CD163 is an excellent marker for confirming histiocytic differentiation and is useful in eliminating morphologic mimics such as Spitz nevi from the differential diagnosis. The lack of CD163 in atypical fibroxanthomas argues against a histiocytic origin for this tumor.

The distinction between dermatofibroma, particularly cellular variant, and dermatofibrosarcoma protuberans in excisional biopsies is usually straightforward. However, a separation between the two may be sometimes challenging, especially in superficial biopsies. Although factor XIIIa and CD34 immunostains are useful in differentiating dermatofibroma and dermatofibrosarcoma protuberans in most instances, focal CD34 positivity may be seen in cellular fibrous histiocytoma. Some cases reveal overlapping immunostain results. D2-40 identifies a 40-kDa O-linked sialoglycoprotein present on a variety of tissues including testicular germ cell tumors as well as lymphatic endothelium. In this study, we investigated the utility of D2-40 in separating dermatofibroma from dermatofibrosarcoma protuberans and compared the results with other commonly used immunostains. Fifty-six cases of dermatofibroma (including six cellular variant) and 29 cases of dermatofibrosarcoma protuberans were retrieved from the archives of Department of Anatomic Pathology at Sunnybrook Health Sciences Center in University of Toronto. We applied factor XIIIa, CD34, and monoclonal mouse anti-D2-40 immunostains to formalin-fixed, paraffin-embedded tissue sections. All 56 (100%) cases of dermatofibroma demonstrated strong and diffuse immunoreactivity to D2-40 in the spindle cells and stroma. Similarly, factor XIIIa showed strong and diffuse positivity in the spindle cells. Nearly all dermatofibromas were negative for CD34 except one case revealing focal positivity. None of dermatofibrosarcoma protuberans cases were labeled by D2-40, although four cases showed weak and patchy background staining in contrary to diffuse, strong, and crisp staining seen in dermatofibromas. Our results indicate that D2-40 seems to be a sensitive immunohistochemical marker for dermatofibromas, including cellular variant. Focal and faint D2-40 staining may be seen in the stroma of dermatofibrosarcoma protuberans. Our findings suggest that D2-40 can be used as a complementary immunostain to factor XIIIa and CD34 in problematic and challenging cases on superficial biopsies.

Angiomatoid fibrous histiocytoma is a neoplasm of uncertain histogenesis, which most commonly arises in the subcutaneous tissue of the extremities of children and young adults. We report the first case of a calcifying sclerosing variant of this entity. This case arose in bone-a site where there has been just 1 previously published case of typical (nonsclerosing/mineralizing) angiomatoid fibrous histiocytoma. The patient presented with the classical paraneoplastic syndrome that can occur with this tumor type and, apart from the described extracellular matrical features, displayed typical histologic features. Due to the rarity of angiomatoid fibrous histiocytoma at this site and the presence of matrical sclerosis/mineralization, this case raised the important differential diagnosis of osteosarcoma, both histologically and radiologically. The diagnosis was confirmed by molecular analysis; fluorescence in situ hybridization for EWSR1 gene disruption, and reverse transcription-polymerase chain reaction using newly designed primers on both frozen and decalcified, paraffin-embedded tissue samples showing an EWSR1-ATF1 translocation. It is important to recognize that this relatively indolent tumor can arise in bone and that it can contain focally mineralized hyalinized sclerotic matrix to avoid making the serious misdiagnosis of high-grade osteosarcoma and administering aggressive systemic chemotherapeutic treatment.

Background: We report a case of atypical fibroxanthoma that developed in the palpebral conjunctiva., Case: A 94-year-old woman had a hemorrhagic tumor in the right lower palpebral conjunctiva that was resected, and adjunctive cryotherapy was applied to the surgical bed., Observations: The tumor was bleeding and appeared as a pale red, elastic but firm nodule approximately 15x16x8 mm in size. It was composed mainly of fibroblast-like cells and pleomorphic histiocyte-like cells. A storiform pattern was observed in the fibroblast-like cells. The tumor stained positive for vimentin, CD68, and CD10, weakly for CD74 and CD99, and was negative for keratin (wide), KL-1, alpha-fetoprotein, myoglobin, S-100, alpha-smooth muscle actin, desmin, leukocyte common antigen, and glial fibrillary acidic protein immunohistochemically. The MIB-1 index was about 10%. From these findings, we diagnosed the tumor as an atypical fibroxanthoma. There has been no recurrence in the 2 years since the resection., Conclusions: An atypical fibroxanthoma in the palpebral conjunctiva is very rare. The clinical presentation and histological and immunohistochemical studies are helpful in distinguishing between an atypical fibroxanthoma and a malignant fibrous histiocytoma.

Atypical fibroxanthoma (AFX) (dermal pleomorphic sarcoma) remains a somewhat controversial entity. Some authors have averred that AFX is a fiction, suggesting that such lesions merely represent misclassified examples of spindled squamous cell carcinoma. In addition, the immunoperoxidase confirmation of AFX has been less than straightforward and has historically been approached as a diagnosis of exclusion because of the lack of sensitivity and specificity of available "positive" reagents. Procollagen 1 (PC1) and CD10 represent recently developed immunoperoxidase reagents that have been forwarded as useful in this setting, and we sought to characterize our experience, both to confirm the utility of these antibodies and to compare them. Our investigation included 3 separate data sets. Group 1 consisted of a retrospective review of 98 consecutive cases in which PC1 was used in the evaluation of dermatopathology specimens in routine practice during a 13-month interval. Group 2 consisted of a direct comparison of 11 AFX, 11 dermatofibroma (DF), and 7 epithelioid dermatofibroma (EDF) using the CD10 reagent on cases identified by database search. Group 3 consisted of a retrospective review of 47 cases in which CD10 was used in routine practice during a 10-month interval. Group 1 included 47 AFX, 13 carcinomas, and 6 melanomas. PC1 expression was observed in 45 of 47 AFX (96%), with a strong reaction in 78% of cases. Among a comparison group of carcinomas, 13 of 13 displayed strong keratin immunopositivity and 11 of 13 (85%) lacked PC1 expression whereas 2 showed focal weak labeling. Six of six melanomas exhibited avid S100 expression and none labeled with PC1. In group 2, strong CD10 immunoreactivity was present in 11 of 11 AFX. Similarly, 11 of 11 DFs were also positive. In contrast, 6 of 7 cases of EDF lacked CD10 expression. Group 3 included 38 AFX and 9 miscellaneous spindle cell proliferations. Of the 38 AFX, 37 (97%) labeled with CD10 and in 34 (92%) the reaction was strong. PC1 immunostaining was also completed in 34 of 38 AFX from group 3 and 27 (79%) cases showed positive labeling. Our results confirm that both PC1 and CD10 can be used as positive markers of AFX. We believe that CD10 and PC1 immunostaining can be used as a useful adjunct to supplement the diagnosis of AFX, within the context of an immunoperoxidase panel. Not surprisingly, CD10 expression is also common in DF, a benign analog of AFX, with the exception of its epithelioid variant. In direct head-to-head comparison, our experience indicates that the staining of AFX with CD10 is more avid than that observed with PC1. Lastly, out data includes over 80 examples of AFX, <5% of which showed keratin labeling. Given a general lack of keratin expression, it seems unlikely that AFX merely represents poorly differentiated squamous carcinoma.

A 48-year-old man was referred for investigation of an asymptomatic radiolucent lesion in the mandible. The margin was partly irregular, and there was no peripheral sclerosis. The tumour was composed of histiocytic cells, spindle cells, and fibrous tissue. Immunohistochemical analysis showed that the tumour cells stained for CD68 and vimentin, and not for cytokeratin, smooth muscle actin, S-100 protein, or CD34. The tumour was therefore diagnosed as a benign fibrous histiocytoma.

More recent techniques to characterize the genetic profile of soft-tissue tumors include the use of gene arrays. Using this technique, Apolipoprotein D (Apo D), a 33-kDa glycoprotein component of high-density lipoprotein, has been found to be highly expressed in dermatofibrosarcoma protuberans. To corroborate these results, we sought to ascertain the utility of Apo D by investigating its sensitivity and specificity in a variety of CD34-positive and CD34-negative cutaneous neoplasms including superficial acral fibromyxoma, sclerotic fibromas, and cellular dermatofibromas. Of interest, we found absence of Apo D expression in all four cases of superficial acral fibromyxoma. Of the remaining CD34-positive lesions, Apo D expression was noted in 35/36 (97%) cases of dermatofibrosarcoma protuberans, 3/5 (60%) giant-cell fibroblastomas, 4/4 (100%) sclerotic fibromas, 8/8 (100%) neurofibromas, and 1/1 (100%) solitary fibrous tumor. Of the CD34-negative lesions, Apo D expression was noted in 2/22 (9%) regular dermatofibroma, 23/45 (51%) cellular dermatofibroma, 10/10 (100%) malignant fibrous histiocytoma, 9/10 (90%) atypical fibroxanthoma, 7/8 (86%) cellular neurothekeoma, 9/9 (100%) malignant melanoma, 8/8 (100%) melanocytic nevi (100%), 0/2 superficial angiomyxoma, 0/15 fibromatosis, 0/1 nodular fasciitis, and 1/2 (50%) desmoplastic fibroblastomas. In summary, our findings indicate that Apo D expression is not specific to dermatofibrosarcoma protuberans. Its principal use as an immunohistochemical adjunct lies in its utility in differentiating superficial acral fibromyxoma from dermatofibrosarcoma protuberans. Although strong positive staining of Apo D in a markedly atypical fibrohistiocytic lesion is suggestive of atypical fibroxanthoma and/or malignant fibrous histiocytoma, further studies with the inclusion of other atypical spindled cell neoplasms are required to conclusively prove the same.

Multiple eruptive dermatofibromas are a rare presentation of dermatofibroma which are frequently associated with underlying diseases such as human immunodeficiency virus infection or lupus erythematosus. Eruptive dermatofibromas generally present a characteristic histology with a poorly circumscribed lesion showing hyperplasia of the epidermis, prominent bundles of collagen and a diffuse proliferation of fibrocytes. We report an unusual case of multiple eruptive dermatofibromas showing massive depositions of mucin within the dermis. A 20-year-old woman presented with nearly 100 red to yellowish papules and nodules distributed symmetrically all over the integument which developed over a period of 9 years. Comprehensive clinical and laboratory diagnostics showed no signs indicating any underlying disease. To our knowledge this is the first report of multiple eruptive myxoid dermatofibromas. We consider this case to be a unique presentation of multiple eruptive dermatofibroma showing massive deposition of mucin.

Dermatofibroma (DF) or cutaneous fibrous histiocytoma is a common benign skin tumor that exhibits multiple, distinct histologic variants. Although clear cell DF has been described in the literature, balloon cell degeneration causing a clear cell DF phenotype has been not been reported to date. Herein, we describe the clinicopathologic findings of balloon cell DF arising on the heel of a 43-year-old man. Clinically, it presented as enlarging tan-white, ulcerated, firm 1.5 cm nodule, clinically suspected to be pyogenic granuloma. Excisional biopsy revealed a circumscribed fibrous tumor populated by mostly clear and spindle cells. A zonal arrangement separated the varied tumor cells where the most superficial, polypoid area showed large, clear polygonal balloon cells; the mid-dermal zone demonstrated a transition between balloon cells, epithelioid cells, and spindle cells; and the deep dermal zone had storiform arrangement of spindle cells, with the fascicles separated by coarse collagen bundles. A CD10+ > CD68+ > Factor XIIIa+ immunophenotype was identified with negative immunolabeling for S-100 protein, HMB-45, cytokeratin AE1/AE3, desmin, smooth muscle actin, lysozyme, and leukocyte common antigen (LCA). Ultrastructurally, the clear tumor cells were filled with multiple, empty, nonmembrane bound vacuoles of varying size. No recurrence has been described after complete excision and 7 months of follow up. DF with balloon cell change, likely secondary to persistent irritation, should be added to the differential diagnosis of cutaneous primary and metastatic neoplasms showing balloon cell degeneration such as balloon cell melanocytic nevi and renal cell carcinoma, respectively.

Fibrous histiocytoma, a primary mesenchymal tumor of the orbit, is known to arise from various ocular and adnexal tissues. We are unable to find a published report of this tumor originating from the lacrimal gland. We report a case of a benign fibrous histiocytoma of the lacrimal gland in an 11 year old girl who presented with painless, progressive eyelid swelling and mild proptosis. Imaging studies revealed a discrete mass in the lacrimal gland region. The tumor was completely excised by anterolateral orbitotomy. Light microscopy showed a spindle cell tumor arising from the lacrimal gland. The tumor cells were arranged in a characteristic storiform (cartwheel) pattern with no pleomorphism or mitotic figures. Immunohistochemically, the tumor cells were focally positive for CD-68 and negative for S-100, smooth muscle actin, vimentin, and CD-34, which ruled out neurofibroma, leiomyoma, solitary fibrous tumor, and hemangiopericytoma. Based on these features, a diagnosis of benign fibrous histiocytoma was made.

Sclerosing hemangioma (SH) with endobronchial growth (SH-EG) is an extremely unusual form of SH. A case of SH-EG in a 47-year-old female is described. She suffered from a productive cough for 4 months. A chest CT scan revealed a well-circumscribed, parenchymal mass with endobronchial lesions continuously extending to the right main bronchus. Right upper sleeve lobectomy was carried out. The tumor was 4.8 x 3.5 cm in size, tan-brown, and elastically soft. It was located in the pulmonary parenchyma of the right upper lobe and continuously extended to the right upper bronchus. Furthermore, the main tumor also spread into segmental bronchi and peripheral bronchioles. Microscopically, the tumor consisted of round to cuboidal cells with papillary and solid patterns, partly showing sclerosis and hemorrhage. For 2.5 years after surgery, the patient has been well without recurrence or metastasis. Florid intrabronchial extension as seen in this case has never been documented in SH. To form an endobronchial component, it seems to be crucial that the parenchymal SH is located adjacent to the bronchus and involves it, followed by the destruction of the bronchial cartilage.

Purpose: To review the clinical features and course of six patients with fibrous histiocytoma (FH) of the conjunctiva., Design: Retrospective, observational clinical case series., Methods: Chart review of six consecutive patients with unilateral cases of conjunctival FH was conducted. Clinical presentation, treatment, histopathologic condition, and follow-up information were recorded., Results: The mean patient age was 37 years (median, 38 years; range, 12 to 72 years). There were five white patients, one black patient, five male patients, and one female patient. The tumor was present for a mean of three months (median, five months; range, one to 12 months) and was unilateral (one right eye, five left eyes). In all cases, the tumor was a tan, dome-shaped limbal mass in the conjunctival stroma with visible intrinsic vessels. The mean tumor basal dimension was 7 mm (median, 5 mm; range, 4 to 11 mm). Surgical resection was performed in all cases, and histopathologic study demonstrated benign FH in four cases and malignant FH in two cases. Those cases with benign FH showed no recurrence over nine months (median, eight months; range, three to 18 months). One patient with malignant FH showed recurrence and required repeat excision. The other patient with malignant FH was treated with plaque radiotherapy to maintain control. There was no evidence of orbital invasion or remote metastasis in any case over the mean follow-up period of 21 months (median, 10 months; range, three to 80 months)., Conclusion: FH is a rare conjunctival tumor that can show benign or malignant features. Complete resection is advised. Malignant FH can demonstrate recurrence that necessitates wide resection and radiotherapy.

We report the case of a 19-year-old pregnant woman who presented with a nipple tumor. The lesion consisted in a spindle-cell proliferation with histologic features similar to those of fibrous histiocytoma, with a highly vascularized stroma. Although it showed low mitotic activity, scattered marked atypical cells with prominent nucleoli were identified, thus raising concern about the benign nature of the tumor. Immunohistochemical evaluation revealed that the spindle cells were diffusely positive for vimentin, focally positive for CD68, and negative for all the other tested antibodies. The patient had a total excision of the lesion and she is free of disease after 30 months. To our knowledge this is the first reported case of a lesion of this type in the nipple after body-piercing., (Int J Surg Pathol 14(1):89-93, 2006.)

Background: Plexiform fibrohistiocytic tumor is a soft-tissue tumor of intermediate malignancy occurring in children and young adults but is only rarely found in infants. The tumor usually involves the upper limbs and is slow growing and painless. Recurrence rate is high. Lymph node and systemic metastases can occur, but have never been reported in infants. Clinical behavior in infancy is not known. Histologically, the tumor is characterized by nodules of histiocyte-like and multinucleated cells and fascicles of spindle cells arranged in a plexiform pattern. Mitosis, atypia, and nuclear pleomorphism are common but not pronounced., Methods and Results: We report three cases in infants, one of which is congenital, having an unusual topography and a broad histological spectrum., Conclusion: In infants, wide excision with large safety margins should be performed as the behaviour of this tumor remains uncertain. Leclerc S, Hamel-Teillac D, Oger P, Brousse N, Fraitag S. Plexiform fibrohistiocytic tumor: three unusual cases occurring in infancy.

Background: Basaloid epidermal proliferations (BEP), morphologically resembling basal cell carcinoma (BCC), have been described overlying dermatofibromas. Distinguishing the two is important because of non-aggressiveness of BEP and local aggressiveness of BCC. The aim of this study is to determine whether CK20 antibody staining for Merkel cells can be used as an adjunct method to differentiate BEP from BCC., Methods: Ten cases of BEP overlying dermatofibromas were selected. Ten cases of BCC were used as control. The two groups were stained with CK20 antibody. Numerical density of CK20 stained Merkel cells in peri-lesional epidermis, BEP and BCC was determined by examining 300 cells at 400X in two separate areas by three independent pathologists. To determine statistical significance, the results were compared using t-test method., Results: Density of Merkel cells in peri-lesional epidermis was 0.2-0.3%. No merkel cells were detected in the BCC. BEP overlying dermatofibromas showed an obvious increase in CK 20 stained Merkel cells. The difference was statistically significant (P < 0.02) CONCLUSIONS: We report a significant increase in CK20 stained Merkel cells in BEP overlying dermatofibromas as compared to BCC. CK20 antibody staining for Merkel cells can be used as an adjunct method to differentiate BEP overlying dermatofibromas from BCC. Mahmoodi M, Asad H, Salim S, Kantor G, Minimo C. Anti-CK20 staining of Merkel cells helps differentiate basaloid proliferations overlying dermatofibromas from basal cell carcinoma.

Myxofibrosarcoma or myxoid malignant fibrous histiocytoma is one of the most common fibroblastic sarcomas in older patients. It is characterized by a tendency for predominantly subcutaneous, multinodular, diffusely infiltrative growth, which may extend to the overlying dermis and present as a cutaneous lesion. Histologically, it comprises a spectrum ranging from hypocellular low-grade myxoid to high-grade pleomorphic sarcoma. Because the dermal presentation usually appears relatively banal, accurate diagnosis is sometimes challenging. In this report, we present two cases of myxofibrosarcoma with dermal involvement.

The epithelioid cell histiocytoma (ECH) is a polypoidal benign tumor of superficial connective tissue that is often diagnosed as a pyogenic granuloma. ECHs are speculated to originate from dermal dendritic subunits and are composed of 2 primary cell populations, ie, CD34+ primitive fibroblastic dendrocytes and factor XIIIa+ histiocytes. Although dendritic subunits are distributed throughout most collagenous tissues inclusive of oral mucosa, to date, all reported cases of ECH have been cutaneous lesions. ECHs' putative pathogenesis entails activation of CD34+ "sentinel" reserve dendrocytes, followed by an influx of histiocytes and mast cells. Juxtacrine communication increases release of wound healing factors; suggesting a reactive etiologic component. In this current case, the location (ventral tongue) and history (recent increase in size) suggest the possibility that trauma could have initiated the dendritic subunit "wound healing" cascade. Consistent with its benign course, the ECH is managed by local excision, and has an excellent prognosis.

We report on two patients with granular cell atypical fibroxanthoma. Both neoplasms were solitary, light-tan, dome-shaped papules on sun-exposed areas of the head in two elderly white men. Microscopically, these neoplasms showed a dermal proliferation of pleomorphic granular cells with irregular hyperchromatic nuclei, multinucleated cells, and scattered mitoses. Immunohistochemical stains were positive for CD68 and vimentin and negative for Melan-A or human melanoma black (HMB)-45, S-100 protein, pancytokeratin, and actin, consistent with atypical fibroxanthoma. The differential diagnosis of granular cells in neoplasms containing cytological pleomorphism is challenging in view of the many different neoplasms that may present with granular cytoplasm. These include the conventional granular cell tumor and its malignant form, leiomyoma, leiomyosarcoma, dermatofibroma, dermatofibrosarcoma protuberans, and angiosarcoma.