Uterine endometrioid adenocarcinoma with extensive pilomatrixoma-like areas. A case report.

Shadow cells are typical features of pilomatrixoma, although they have been described in other benign cutaneous tumours with characteristics of differentiation toward the hair matrix. The finding of extensive shadow cell differentiation in visceral carcinomas is otherwise unusual. We report herein a case of uterine adenocarcinoma with extensive pilomatrixoma-like areas in a 74-year-old woman. The endometrial tumour showed an invasive poorly differentiated growth with squamous differentiation deeply extending into the myometrium intermixed with lobules of empty squamoid polyhedral cells with clear shadow like nuclei, focally exhibiting a 'ghost' appearance. The cervix, salpinges, ovaries and pelvic lymph nodes were free of disease and, taking all evidence into account, the tumour was diagnosed as poorly differentiated endometrial endometrioid adenocarcinoma (FIGO stage IB). The recognition of an extensive pilomatrixoma-like component in a high- grade endometrioid adenocarcinoma may be important to avoid diagnostic misinterpretation with uterine metastases of malignant cutaneous pilomatrical tumours, such as pilomatrix carcinomas.