Pathology of Pilomatrixoma
Syn: Pilomatricoma ; Calcifying epithelioma of Malherbe
Pilomatrixoma is a very common benign adnexal tumour with matrical differentiation.
Both ultrastructurally and histochemically these are similar to hair matrix.
Most cases are associated with beta-catenin gene mutations.
Solitary and rarely multiple rubbery nodules (usually 5mm to 2cm in diameter).
The tumour usually occurs in the first two decades of life. Often diagnosed as epidermoid/pilar cysts.
May be associated with Gardner's syndrome or myotonic dystrophy. Usually multiple lesions are present.
A distinctive proliferative variant of pilomatrixoma ;
This is a relatively large lesion in the dermis which sometimes extend to the subcutis ;
Composed of lobular proliferation of basaloid cells in association with adjacent focal areas containing eosinophilic, cornified material with shadow cells ;
In some cases there are relatively large areas of shadow cells whereas, in others there are only small foci of shadows cells ;
Basaloid cells show variable nuclear atypia and mitotic figures ;
Architectural pattern of the neoplasms is different from that of a large fully developed pilomatrixoma with a cystic character and basaloid cells predominantly aligned at the periphery.
diagnosis: Matricoma, basal-cell carcinoma with matrical
differentiation, and matrical carcinoma (pilomatrical carcinoma).
Related post: Pilomatrix Carcinoma
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