Scalp pilomatrix carcinoma as an extra-axial mass.

We report the CT, MRI, and angiographic findings in a case of pilomatrix carcinoma that had invaded the temporal bone and presented itself as an extra-axial mass. Even though bone destruction was better shown with CT, the tumor mass with its meningeal and tentorial extension was seen more clearly with MRI. The arteriogram demonstrated a unique vascular supply from the external carotid artery.

Flow cytometric DNA content analysis of a case of pilomatrix carcinoma showing multiple recurrences and invasion of the cranial vault.

Pilomatrix carcinomas are rare neoplasms of the skin that may be locally aggressive or metastatic. The differentiation of these tumors from benign pilomatrixomas depends on a constellation of microscopic features, some of which may be equivocal or absent in individual biopsy specimens. We encountered a tumor with distinct pilomatrix differentiation (lobulated nests of basaloid cells, ghost cells, focal calcification) that recurred multiple times and ultimately invaded the cranial vault. Despite this aggressive behavior, the tumor was difficult to separate from benign pilomatrixoma on morphologic grounds. Because DNA content flow cytometry has proved useful in the prediction of aggressive behavior in various solid tumors, we analyzed this neoplasm by flow cytometry. Neither aneuploid peaks nor a high proliferative fraction were seen in this example of pilomatrix carcinoma.