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Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a distinct type of peripheral T-cell lymphoma, which has gained recognition over the past decade. The disease presents complex clinical, pathologic, and immunohistochemical features, which warrant awareness by dermatologists, dermatopathologists, hematopathologists, hematologists, oncologists, and internists. SPTCL was initially included as a provisional entity in the Revised European-American Lymphoma classification, followed by the European Organization for Research and Treatment of Cancer classification as a primary cutaneous lymphoma, and subsequently as a distinct entity by the World Health Organization classification. It is known that patients diagnosed with SPTCL usually respond poorly to therapy, and the tumor progresses aggressively. Data from recent studies in a series of cases of SPTCL by the European Organization for Research and Treatment of Cancer Cutaneous Lymphoma Group have further identified SPTCL as a heterogeneous disease entity, which comprises an alpha/beta subtype (SPTCL-AB) and a gamma/delta subtype (SPTCL-GD). The latter has recently been included in the entity of "cutaneous gamma/delta T-cell lymphoma" by the World Health Organization, Pathology and Genetics of Skin Tumours. The clinical, histologic, and immunophenotypic data, treatment, and prognosis, appear different in the 2 subtypes of SPTCL. We report a case of fatal SPTCL-GD (cutaneous gamma/delta T-cell lymphoma), with detailed clinicopathologic features, immunohistochemical studies, treatment, and clinical course. In view of its aggressive behavior, identification of this disease is critical for proper management and treatment.

Keratoacanthomas are benign skin tumors that grow rapidly but eventually regress. They occur most commonly in sun-exposed skin and are histologically remarkably similar to squamous cancers. Since mutations of the p53 tumor suppressor gene are found frequently in cutaneous squamous cell carcinomas, we hypothesized that p53 mutations might contribute to the development of keratoacanthomas. To address this question, we did p53 immunohistochemistry with a polyclonal rabbit antiserum, CM-1, that binds both mutant and wild-type p53 proteins. Although wild-type p53 protein degrades rapidly and is generally undetected by immunohistochemistry, mutant p53 protein has a longer half-life and accumulates to detectable levels. We tested 26 formalin-fixed keratoacanthomas and 4 normal skin biopsies. Positive nuclear staining was detected in 20 of 26 (77%) of the keratoacanthomas and in none of the normal skin samples. Nuclear staining occurred in the outermost layer of the neoplasms and not in the keratin-filled central cores. Since nuclear p53 protein within a cutaneous squamous cell carcinoma usually correlates with missense mutation, these data suggest that p53 mutations contribute to the development of this benign neoplasm. The histologic similarity to squamous cell carcinoma and the accumulation of p53 protein suggest progression toward malignancy, but the invariable regression of these tumors suggests an arrest at some point in multistage carcinogenesis. If this model is correct, then genetic analysis of keratoacanthomas may provide clues to the later stages of squamous carcinogenesis including local invasion and metastasis.

We present a rare case of metastatic adenocarcinoma of the parotid gland to the skin. Reviewing the histologic features of the primary parotid gland and comparing the microscopic sections and immunohistochemical studies, we concluded the skin tumor to be metastases from the parotid adenocarcinoma. By histologic examination alone, it is difficult to distinguish an eccrine sweat gland carcinoma from a metastatic carcinoma of the salivary gland. Immunohistochemical analysis may not be conclusive. Therefore, clinical history and clinicopathologic correlation are essential in arriving at an accurate diagnosis in these cases.

The clinical, morphological and immunohistochemical features of 27 patients with anaplastic large cell lymphoma (ALCL) of CD30-positivc type, with cutaneous lesions as the sole initial clinical manifestation, were analyzed. The neoplasm presented as solitary or multiple, usually ulcerated skin lesions, affecting predominantly elderly patients (median age: 67 years) with a male preponderance (male to female ratio of 6:1). In most patients, there was an excellent response to chemotherapy. The cardinal histological features included diffuse dermal and sub-cutaneous infiltration by large, anaplastic tumor cells, all or nearly all of which showed diffuse, strong membrane staining and frequently a paranuclear, dot-like reaction with the CD30 marker (Ber-H2). Epidermal ulceration, pseudo-epitheliomatous hyperplasia and dermal vascular proliferation were also ob-served.

Background: Nephrogenic fibrosing dermopathy (NFD) has emerged as a clinicopathologic entity since 1997 and recently renamed as nephrogenic systemic fibrosis (NSF). The etiology and pathogenesis remain uncertain. Characteristic clinical presentation is described as diffuse thickening and hardening of the skin occurring in patients with renal insufficiency. Typical histological features include proliferation of CD34 positive fibrocytes, increased thick collagen bundles and mucin deposition, without significant inflammatory infiltrate. Variations in clinical presentations have been reported, including papular and plaque-like skin lesions, focal lesion only, as well as systemic involvement. Histological changes can be subtle and non-specific, overlapping with other disease processes and harboring features including calcification and osteoclast-like giant cells with osseous metaplasia. Methods: We reviewed patients with NSF that presented to our dermatology clinic by chart review, clinical examination and histological examination. Skin biopsy specimens were obtained from all cases. Histopathology evaluations were carried out by three dermatopathologists (AD, BS and GK) independently and the features were compared among all the cases. Special stains and immunohistochemistry study were also performed to highlight the histological features. Results: Seven cases of NSF presented with a spectrum of clinical manifestations, from classic diffuse hardening of the skin to localized linear plaques. On histological examination, proliferation of CD34-positive fibrocytes ranged from sparse to dense, collagen bundles ranged from thin to thick, and the interstitial dermal mucin accumulation ranged from scant-patchy to abundant. In addition, the lesion displayed various degrees of vascular proliferation, inflammatory infiltrates and intensities of CD68 and Factor XIIIa staining. Two cases showed extensive dermal calcification and ossification. Conclusion: NSF may present with a spectrum of clinical abnormalities, and exhibit overlapping histopathological features resembling cicatrix and other dermal reparative/regenerative processes. NSF may in fact to be a disorder of aberrant extracellular matrix remodeling in patients with renal insufficiency. Deng A, Bilu Martin D, Spillane A, Chwalek J, St. Surin-Lord S, Brooks S, Petrali J, Sina B, Gaspari A, Kao G. Nephrogenic systemic fibrosis with a spectrum of clinical and histopathological presentation: a disorder of aberrant dermal remodeling.

The diagnosis of skin diseases, particularly inflammatory dermatoses, is based primarily on clinical information. Pathologic examination of the biopsied specimen often serves as a complementary or confirmative part of the diagnosis. However, the clinical diagnosis of skin diseases may be challenging, as the clinical information and appearance of skin lesions invariably overlap. Evidence for a correct diagnosis may be lacking without histopathologic examination of skin biopsies. It is well known that the histologic diagnosis of inflammatory and other skin diseases requires clinicopathologic correlation, and there is evolution of skin lesions into different stages as the diseases progress. Other factors important for accurate dermatopathologic diagnosis are optimum time, best location and preferred techniques of skin biopsy. In searching for available information concerning when, where and how to take skin biopsies, it is noted that there are only limited practical guidelines currently available. We present this review article in hopes that our collective dermatopathologic and dermatologic experience can provide a quick reference for accurate diagnosis and proper management of skin diseases.

The dermatologic diagnosis of Rocky Mountain spotted fever (RMSF) is often presumptive; the clinical presentation includes skin rash and febrile illness with or without a clear history of tick bite. The characteristic cutaneous manifestations include a generalized skin eruption with purpuric, blanching or non-blanching macules and papules usually involving the extremities. Although skin biopsies are often performed to confirm the diagnosis, the spectrum of cutaneous histopathology in RMSF has not been well described. We studied a series of 26 cases of RMSF, of which 10 were surgical specimens and 16 were autopsies. The microscopic changes were correlated with the duration of illness. The main histopathologic feature was lymphohistiocytic capillaritis and venulitis with extravasation of erythrocytes, edema, predominantly perivascular and some interstitial infiltrate. Leukocytoclastic vasculitis (LCV) with neutrophilic infiltrate and nuclear dust was seen in 11 of 15 (73%) specimens from involved skin. These lesions with LCV also showed notable epidermal change including basal layer vacuolar degeneration with mild dermoepidermal interface lymphocytic exocytosis. Six lesions with LCV displayed focal fibrin thrombi and capillary wall necrosis. Apoptotic keratinocytes were noted in 3 lesions with LCV. Subepidermal blister was observed in the skin lesion of an autopsied patient with LCV changes. Another lesion of a fatal case with LCV also contained features of acute neutrophilic eccrine hidradenitis. Focal small nerve twig inflammation was noted in a third autopsy case with LCV. Plasma cells were seen in 6 of 34 specimens (18%); and eosinophils were observed in 3 (9%). The subcutaneous fat contained a mild perivascular inflammation and one case revealed focal lobular neutrophilic inflammation. Immunohistologic (IH) staining using polyclonal rabbit anti-Rickettsia rickettsii demonstrated positive staining of the organisms in the affected endothelial cells in all 12 cases tested. The cutaneous histopathology of RMSF is caused by endothelial damage by the rickettsial organisms which elicit an initial lymphohistiocytic small vessel vasculitis with progression to LCV. The vasculitis in RMSF is, therefore, considered to be a form of septic vasculitis.

Eccrine spiradenoma (ES) rarely (less than 1%) occurs in infancy. These tumors differ from the conventional ES by the presence of superficial dermal nodules which display a less distinct two-cell pattern of immature adnexal epithelial cells and rarely ductule formation. These tumors may be mistaken for mesenchymal neoplasms involving the skin and subcutis of infants and young adults. Recognition of the histopathologic features and immunostains are required to make a definite diagnosis. We describe 2 cases of ES occurring in patients younger than one year. Detailed histopathologic and histochemical differential features of these tumors and mesenchymal neoplasms of the skin and subcutis commonly occurring in infants and young adults are discussed. The biologic behavior of infantile ES is benign, but complete excision is recommended to prevent recurrence. We speculate that these tumors may represent congenital hamartomatous growths.

Ultrastructural studies of Kaposi's sarcoma (KS) from skin biopsies of 24 patients (eight with acquired immunodeficiency syndrome (AIDS) and 16 without) were performed to delineate the nature of hyaline globules and vascular slits. These structures have been regarded as one of the important criteria for the recognition of KS under light microscopy. Histochemical and immunochemical studies were also performed to correlate with the electron microscopic (EM) observations. The most remarkable EM findings of KS were the intracytoplasmic lumen formation and erythrophagocytic activities of the neoplastic cells, particularly in the mature nodular, or neoplastic stage. The spindle-shaped or ovoid neoplastic cells frequently contained one to several intact and fragmented red blood cells. The intracellular and extravasated erythrocytes were often arranged in single files, giving these vascular slits an elongated appearance on longitudinal sections. The phagocytic activities of the neoplastic cells were demonstrated by the presence of membrane-bound lysosomes containing phagocytized erythrocytes and their partially digested forms (erythrophagosomes) adjacent to pinocytotic vesicles, prominent rough endoplasmic reticulum, and Golgi apparatus, as well as scattered, small, membrane-bound lysosomal granules, some of which were attached to the erythrophagosomes. The erythrophagosomes underwent various stages of disintegration. The partially digested red cells varied from 0.4 to 10 microns in diameter. The results of histochemical and immunochemical findings also strongly suggested that erythrophagosomes were most likely the hyaline globules (bodies) seen in light microscopy. The exact mechanism of erythrophagocytosis is uncertain. However, its consequences, erythrophagosomes, and intracytoplasmic lumen formation, particularly in the nodular or neoplastic stage in patients with and without AIDS, are among the important histologic features of KS.

Squamous-cell carcinoma may arise in scars of chronic discoid lupus erythematosus. Although there have been 19 cases reported previously, detailed histopathologic features of this entity have not been recorded. We report a patient with extensive chronic discoid lupus erythematosus involving the scalp with subsequent development of multiple squamous-cell carcinomas. The tumors were locally aggressive with recurrences and invasion into the underlying skull and dura. The patient died of respiratory failure 4 1/2 years after initial surgical treatment. There was no clinical evidence of metastasis. Squamous carcinoma arising in discoid lupus erythematosus can be regarded as a low-grade carcinoma. Although about 20% of patients developed local recurrences and metastasis developed in about 30%, fatality occurred in only two patients (10.5%). Pertinent literature is reviewed, and the histopathologic findings, differential diagnosis, and biologic behavior of this tumor are discussed.

Epithelial atypia is rarely encountered in ovarian cystadenofibromas. Ten examples are reported with cytological features identical to serous tumors with low malignant potential. In two neoplasms the epithelium resembled an atypical endometrial hyperplasia, and one of these had squamous metaplasia. These two neoplasms probably qualify as endometrioid tumors of low malignant potential. None of the 10 patients had recurrence following excision of their neoplasm, and no similar patients have been encountered with neoplasms in more advanced stages. Even though aggressive behavior has not yet been established, the histologic features suggest a low degree of malignant potential and long-term follow-up of patients is warranted. Cystadenofibromas iwth epithelial atypia probably have less malignant potential than serous tumors of low malignant potential possessing the same epithelial characteristics because cystadenofibromas with atypia have less epithelial surface area and the epithelium is enveloped by connective tissue more than it is in serous tumors of low malignant potential.

Paget's disease may occur at mammary and extramammary sites. Mammary Paget's disease typically involves the nipple and adjacent skin. Almost all such cases are associated with an underlying ductal carcinoma of the breast. A case of Paget's disease occurring at the site of an ectopic breast adjacent to a supernumerary nipple and associated with an underlying intraductal carcinoma is described. A search of the literature revealed no previous report of such cases. Detailed clinical history and histopathologic, histochemical, and follow-up information on this case are presented. The literature on mammary and extramammary Paget's disease is reviewed.

Fifty-seven examples of a rare eccrine sweat gland tumor (aggressive digital papillary adenoma and adenocarcinoma) were studied by means of light microscopy, electron microscopy, and immunoperoxidase techniques. The neoplasm occurred as a single, painless mass, almost exclusively on the fingers, toes, and adjacent skin of the palms and soles. Microscopic features were distinct from those of other eccrine sweat gland tumors and often led to the diagnosis of such metastatic carcinoma as that of the breast. The characteristic histologic features included tubuloalveolar and ductal structures with areas of papillary projections protruding into cystic lumina. The stroma varied from thin, fibrous septae to areas of dense, hyalinized collagen. Forty tumors were classified as adenoma (ADPA) and 17 as adenocarcinoma (ADPAca). Histologically, ADPAca was distinguished from ADPA by its poor glandular differentiation and by necrosis, cellular atypia and pleomorphism, invasion of soft tissue and bone, and invasion of blood vessels. Eighteen (50%) patients with ADPA and 8 (47.0%) who had ADPAca developed recurrent lesions (2 months to 9 years) after surgical removal of the tumor. Seven (41.2%) patients with ADPAca developed metastases, of which 5 involved the lung. Three patients died of metastases, 5 to 20 years after surgical treatment of the primary tumor. The histologic malignant features in ADPAca are indicative of potential for distant metastasis and fatality. The recognition of aggressive digital papillary adenoma and adenocarcinoma as a distinct clinicopathological eccrine sweat gland neoplasm is important because of the potential for aggressive local growth and distant metastasis.

Focal acantholytic dyskeratosis (FAD) is a distinctive histologic pattern characterized by suprabasilar clefts surrounding dermal papillae (villi), acantholytic and dyskeratotic cells at all levels of the epidermis, hyperkeratosis, and parakeratosis. The features of FAD are typically seen in Darier's disease, warty dyskeratoma, and transient acantholytic dermatosis; they are also present in a variety of cutaneous neoplastic and nonneoplastic lesions. FAD, however, has not been previously described in lesions of inflammatory dermatoses. We report a case of FAD occurring in lesions of pityriasis rubra pilaris (PRP). To the best of our knowledge, this is the first reported case of this kind. We also review the pertinent literature.