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These are very rare variants of amelanotic or virtually amelanotic melanoma where a primary melanoma or a metastasis shows partial (DN) or complete loss (UN) of recognizable histological and immunohistochemical features. The histology may lead the pathologists to consider lymphoma, sarcoma, anaplastic carcinoma or a small cell tumor. Some examples of rhabdoid melanoma & melanoma…
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The term is used when 2 or more nevus subtypes are present in a a single lesion (phenotypic heterogeneity). It is mostly seen in commmon nevi, less often in congenital nevus, dysplastic nevus & Spitz nevus. The most commonly encountered combination is with deep penetrating nevus but combinations with blue & cellular blue nevi &…
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An exceedingly rare collision tumor composed of an admixture of squamous cell carcinoma/basal cell carcinoma/trichoblastoma respectively and melanoma. Although most appear to have behaved in a benign fashion, a malignant basomelanocytic tumor is illustrated below. More cases will be need to be stidies/published before the true biological behavior of this group of tumors can be…
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This is a very rare tumor with only 31 cases documented in the literature. It consists of an admixture of matricial cells & usually, heavily pigmented dendritic cells although in some cases, eithelioid melanocytes may also be present. Clinical features •Purple-black papulonodule (O.2-2.5 (mean 0.8 cm) •Elderly (28-92 (median age 70) •M>F •Sun damaged skin…
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Clear cells may be intermingled with balloon cells in balloon cell melanoma. Only very exceptionally is a melanoma be composed of an almost pure cell population- clear cell melanoma. The clear cells differ from balloon cells in that they contain excessive amounts of glycogen which can be confirmed with a PAS stain. Clear cell melanoma…
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All of these lesions are thought to arise as a consequence of impaired migration of melanomcytes from the neural crest to the epidermis. Lumbosacral congenital dermal melanocytosis (Mongolian blue spot, slate gray nevus) Congenital dermal melanocytosis presents as an often large, slate blue colored lesion most often affecting the lumbar & sacral-gluteal region but can…
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Halo nevus, also known as regressing nevus, Sutton’s nevus and leukoderma acquisitum centrifugum represents regression and in usually associated with a common/banal nevus. However it may also be seen with congenital nevus, dysplastic nevus, Spitz nevus, blue nevus and importantly with melanoma. A halo phenomenon may also be seen with a banal/common nevus in the…
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Balloon cell nevus represents the benign counterpart of balloon cell melanoma. Clinical features . Most common in first 3 decades . Head & neck > trunk & extremities although any site may be affected including the mucosae . No sex predilection Histological features .Balloon cell change is most often seen in banal melanocytic nevi but…
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Clinical features •Fairly common affecting 0.6-1.6% of the population •Classified into small (1.5 cm or less in diameter, medium (1.5-20 cm) & large/giant/bathing trunk (>20 cm) •Present at birth & sometimes multiple (satellite lesions) .May be associated with hypertrichosis •Trunk & legs>head & neck, feet & hands . Development of a halo may be associated with spontaneous…
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This is a rare, intraepidermal variant of Spitz nevus. It presents more commonly on the extremities of females as a <6.0 mm, pigmented maculopapule. Age distibution ranges from 15-57 years (mean 34) Histological features •Variable acanthosis •Intraepidermal proliferation of epithelioid Pagetoid cells with plentiful eosinophilic cytoplasm & vesicular nuclei with conspicuous eosinophilic cytoplasm .Retraction artifact…
McKee Derm 