Cbfa1/Runx2 expression in an ossifying basal cell carcinoma of the eyelid

A case of basal cell carcinoma (BCC) with intratumoural bone formation affecting the eyelid of a 77-year-old lady is described. Bone formation in BCCs is an uncommon event. We revised the 23 cases described in the literature: most of them occurred on the face. The pathophysiological mechanism responsible for ossification in cutaneous lesions remains unclear. The bone often develops adjacent to, or within hair follicles. We evaluated the immunohistochemical expression in the present case of Cbfa1/Runx2, an early marker for osteoblastic progenitor cells. A well-developed lamellar bone with adipose bone marrow was observed both in the superficial stroma and intratumourally. Cbfa1/Runx2 was localised in the osteocytes of the heterotopic bone and in the keratin cysts of the BCC. The expression of Cbfa1/Runx2 in the present BCC suggests a possible role of this protein in the induction of the heterotopic bone.