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Mostly located in
the skin of the face, neck and scalp;
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Multifocal tumors
may associate with turban tumor, an autosomal dominant familial
cylindromatosis, may also develop trichoepitheliomas, gene name
CYLD, chromosome 16p;
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"Jigsaw puzzle"
growth pattern, angular cell nests are molded to each other;
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Prominent fibrous
matrix with deposits of eosinophilic, hyaline basement membrane
material surrounding the tumor nests;
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Two cell
populations in each tumor cluster: a compact basaloid cell in
the periphery and a polygonal cell with more amphophilic
cytoplasm in the center. Tumor cells have dispersed chromatin
with inconspicuous nucleoli and sparse mitoses. Hyalinized
globules are common in the tumor clusters.
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