The American Journal of dermatopathology
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Granular cell tumors (GCTs), especially if atypical or malignant, may share cytomorphologic and architectural features with malignant melanoma, when the latter shows granular cell change. In many cases, these neoplasms can be differentiated from each other on histologic grounds, but distinction may sometimes be challenging. By immunohistochemistry, both tumors are strongly positive for S-100 protein and frequently express other nonspecific markers such as CD68, NSE, and NKIC3. ⋯ Melan-A is slightly less specific, with rare cases of GCT showing focal positivity. MITF is not useful in this differential-93% of the GCTs in our series showed nuclear reactivity for this marker. The latter finding highlights the limited specificity of this antibody in the diagnosis of melanocytic tumors.
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Subcutaneous panniculitis-like T-cell lymphoma (SPTCL) is a rare cytotoxic T-cell lymphoma of the skin presenting with histopathologic features simulating those of a lobular panniculitis. The presence of neoplastic T-lymphocytes forming a rim around the individual fat cells in the subcutaneous lobules, so-called "rimming" of adipocytes, is considered a characteristic morphologic feature of this type of cutaneous lymphoma. ⋯ Precise classification of cases with prominent involvement of the subcutaneous tissues can only be achieved upon precise correlation of clinicopathologic and phenotypic features. Rimming of adipocytes should not be considered specific of subcutaneous panniculitis-like T-cell lymphoma.
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Case Reports
Pseudoangiosarcomatous squamous cell carcinoma of skin arising adjacent to decubitus ulcers.
Pseudoangiosarcomatous, or pseudovascular, squamous cell carcinoma of skin is an unusual form of acantholytic (adenoid, pseudoglandular) squamous cell carcinoma that mimics the histolopathologic appearance of angiosarcoma. We report a case of pseudoangiosarcomatous squamous cell carcinoma arising adjacent to decubitus ulcers. ⋯ Because of metastatic disease, palliative measures were undertaken and the patient died four months later. To our knowledge, our patient is the first with pseudoangiosarcomatous squamous cell carcinoma of skin developing within decubitus ulcer.
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Comparative Study
Melan-A: not a helpful marker in distinction between melanoma in situ on sun-damaged skin and pigmented actinic keratosis.
Pigmented actinic keratosis is one of the simulators of early melanoma in situ from severely sun-damaged skin. Close scrutiny of the hematoxylin and eosin stained section does not always allow an unequivocal diagnosis, because it is sometimes difficult to distinguish pigmented keratinocytes from melanocytes. Immunohistochemical stains, such as S-100 and HMB-45, are used routinely to address this problem. ⋯ We therefore believe that Melan-A is a more sensitive marker for intraepidermal melanocytes than S-100, HMB-45, and tyrosinase. In addition there may be expression of Melan-A in keratinocytes and nonmelanocytic cells. To avoid an erroneous diagnosis of malignant melanoma one should therefore interpret results obtained from Melan-A stained slides carefully and in the context with other melanocytic markers.
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As body piercing is increasingly en vogue, complications are on the rise as well. Biopsies of such lesions can impose special problems to the reviewing dermatopathologist. We present two patients who developed papulonodular lesions at the sites of ear piercings. ⋯ These findings suggest that the lesions represent allergic contact granulomas. When confronted with this special type of tissue reaction in skin biopsies of piercing sites, the reviewing dermatopathologist should consider the possibility of an allergic reaction. Careful history and thorough diagnostic procedures, including biopsy of the patch test site can establish the diagnosis of contact allergic granuloma.