Basal Cell Carcinoma With Matrical Differentiation: A Case Report and Literature Review.

Basal cell carcinoma (BCC) with matrical differentiation is an extremely rare subtype of basal cell carcinoma. We present an example of BCC with matrical differentiation and review the relevant literature. A 75-year-old man presented with a rapidly enlarging nodule on his forehead, with the clinical diagnosis of squamous cell carcinoma. Given atypical matrical proliferation on initial biopsy, there was concern for pilomatrix carcinoma. However, a repeat biopsy confirmed a diagnosis of BCC with matrical differentiation. Immunohistochemically, the BCC lobules expressed BCL2 and BER-EP4, while the areas of matrical differentiation showed nuclear β-catenin expression. The tumor cells were negative for keratin 7. BCC with matrical differentiation predominantly affects men, with a mean age of 70 years. Most tumors occur in the head and neck area, and lesions are often slow-growing or asymptomatic. Differential diagnosis includes pilomatrix carcinoma. Outcomes are generally favorable following surgical excision, although 2 instances of lymph node metastasis have been reported.