Malignant transformation in a solitary dermal cylindroma

We describe a case of a solitary dermal cylindroma with focal malignant transformation. The scalp tumor measured 3 cm in greatest dimension and was successfully surgically excised. The patient has been followed up for the last two years with no recurrences. Changes of malignant transformation included loss of peripheral palisading, destruction of the hyaline sheath, areas of necrosis, and pleomorphism of nuclei with frequent mitosis. We reviewed data on 12 other reported cases of dermal cylindromas with malignant transformation. Morphologic features of both benign cylindromas and their malignant counterparts are described. The literature was reviewed regarding the controversy of the cell of origin.