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.

Forty‐six examples of carcinoma cuniculatum, a rare variant of squamous cell carcinoma of the skin, were studied by means of light and electron microscopy and immunoperoxidase techniques. The tumors usually presented as ulcerated, fungating, and polypoid masses with openings of sinus tracts onto the skin surface that exuded foul‐smelling greasy material when pressure was applied. On microscopic examination the tumors were seen to be composed mainly of mature squamous keratinocytes with foci of cellular atypia. Electron microscopic studies revealed features of well‐differentiated squamous cell carcinoma. The tumor may affect any cutaneous area of the body, and there is a predilection for the feet, particularly the soles. The cause must still be determined, but trauma, chronic irritation, and/or viral infection may play a role. The neoplasm is a low‐grade carcinoma capable of local invasion, extension into bone, and rare metastasis to the regional lymph node. Although immunoperoxidase studies revealed no inclusions, infection by human papilloma virus (HPV) remains a possibility.

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Background: Trichodysplasia spinulosa (TS) is a rare, disfiguring skin condition that affects immunosuppressed patients, universally involving the central face. New data point to the recently discovered TS-associated polyomavirus (TSPyV) as the causative agent. Observations:We report a case of TS in a 48-year-old African American man after renal transplant; via polymerase chain reaction and sequencing, confirm the detection of TSPyV in lesional skin; and report the novel detection of TSPyV DNA in renal allograft tissue. Results of polymerase chain reaction analysis were negative for Merkel cell polyomavirus in lesional skin. Fifteen months later, urine cytologic findings showed morphologic evidence of a urinary tract polyomavirus infection. Results of SV40 immunohistochemical analysis were negative in lesional skin, renal allograft, and urine specimens. Conclusions:To our knowledge, this is the first reported case in which TSPyV DNA has been detected in extracutaneous tissues and the third with combined ultrastructural and molecular confirmation of the presence of TSPyV in lesional skin. Lack of detection of other pathogenic human polyomaviruses in this patient's skin supports the specific role of this polyomavirus in the genesis of TS. Further basic science studies are needed to determine the exact pathomechanisms of this polyomavirus and to explore possible tumorigenic roles in other skin diseases.

Eccrine angiomatous hamartoma (nevus) is a rare form of congenital tumorous malformation with proliferation of eccrine secretory coils and ducts, surrounding capillary angiomatous channels and occasionally other minor elements. To date, there have been only about 24 cases reported in the literature. We report an additional case with more detailed description of the microscopic findings, including immunohistochemical observations. The patient was a 28-year-old female who presented with painless, flesh- to reddish brown-colored, violaceous or bluish subcutaneous nodules on the extremities and trunk. The tumors did not show sweating following exertion. The histologic features were comparable to the previously reported cases. The hamartomatous eccrine sweat glands and ducts and a few apocrine glands demonstrated qualitatively diminished antigens commonly found in the eccrine sweat apparatuses, such as carcinoembryonic antigen (CEA) and S-100 protein. The findings of CD34, CD44, human nerve growth factor receptor and Ulex europaeus antigens have not been previously reported. The histologic features suggested a "hamartomatous" growth rather than a true neoplastic process.

Journal of Cutaneous PathologySkin biopsy for inflammatory and common neoplastic skin diseases: optimum time, best location and preferred techniques. A critical reviewThe 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. Sina B, Kao GF, Deng AC, Gaspari AA. Skin biopsy for inflammatory and common neoplastic skin diseases: optimum time, best location and preferred techniques. A critical review.

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