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Commonly seen on the head/neck area of
elderly patients. Tumor often consists of infiltrative spindle cells
that mimic spindle cell melanoma, atypical fibroxanthoma or
leomyosarcoma. A very important hint is that the spindle cells may
continue with the dysplastic epidermis.
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IPX: CK5/6+, but may be
negative
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DDX:
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Spindle cell melanoma
has to be ruled out. Tumor cells may show deep dermal infiltration
with formation of vague fibrotic nodules and lymphocytic aggregation.
Perineural invasion in common. S100+, other malanoma markers not very
helpful.
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Leiomyosarcoma: more
broad, pink cytoplasm, blunt nuclei with perinuclear clearing, SMA+
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Atypical fibroxanthoma:
CD68+, S100-, CK-
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