Basal-Cell Carcinoma With Matrical Differentiation: Report of a New Case in a Renal-Transplant Recipient and Literature Review.

Basal-cell carcinoma with matrical differentiation (BCC-MD) is one of the rarest pathologic variants of basal-cell carcinoma, of which 41 cases have been so far reported in detail. One of them developed in a heart-transplant recipient. We report a new case of BCC-MD occurring in a renal-transplant recipient and review the relevant literature. A 75-year-old white man who had received a renal allograft 7 years ago developed a tumor on the left temple clinically suggestive of basal-cell carcinoma. Microscopically, the tumor associated features typical of basal-cell carcinoma (basaloid lobules with peripheral palisading and clefting) and pilomatricoma (presence of shadow/ghost cells). The 2 tumor components expressed variably beta-catenin, HEA/Ber-EP4, CD10, PHLDA-1, MIB-1/Ki67, calretinin, and bcl-2. BCC-MD has no distinctive clinical features. It affects predominantly male patients with a mean age of 69 years. More than half of cases appear on the head/neck area. Some cases harbor CTNNB1 mutations. Differential diagnosis includes tumors with matrical differentiation, namely pilomatrix carcinoma. The outcome is usually favorable after surgical excision, although regional lymph node metastases developed in 2 patients.