Anti-CTNNB1 (mutation D32Y) Monoclonal Antibody, clone XH024

Background Cutaneous pilomatrical carcinosarcoma (CS) is a very rare biphasic tumor composed of admixed epithelial and mesenchymal malignant cells, with limited information on its pathogenesis. We report a case of pilomatrical CS of the scalp with comparative immunohistochemical and molecular analysis together with a review of the literature. Case presentation A 74-year-old woman presented with a rapidly growing long-standing tumor of the scalp. The tumor was surgically resected. Histologically, the tumor was 25 mm in diameter, and was composed of carcinoma showing a clear pilomatrical differentiation and sarcoma with pleomorphic spindle cells and giant cells. Both epithelial and mesenchymal components shared focal cytoplasmic and/or nuclear accumulation of beta-catenin based on immunohistochemical analysis, although a mutation of exon 3 of the CTNNB1 gene was not detected. Fluorescence in situ hybridization analysis revealed gains of chromosomes 9p21, 3, and 7 in both the epithelial and sarcomatous components. Conclusions The current case demonstrated characteristic findings of pilomatricoma and further evidence of partial clonality between the carcinomatous and sarcomatous component, suggesting the possibility of malignant transformation of pilomatricoma. Rapid growth of a pilomatrical tumor should warrant the development of a malignant tumor, including CS.

Pilomatrixoma, an uncommon, usually benign cutaneous appendageal tumor, shows differentiation toward the hair follicle matrix cell. It undergoes various histopathologic stages, early on displaying epithelial and shadow cells along with granulomatous inflammation. In later stages, illustrated by this unusual case, epithelial cells disappear and are replaced by calcification and ossification. Immunohistochemistry in the current case showed transitional cell reactivity for beta-catenin, probably linking the tumor to a mutation in the beta-catenin gene CTNNB1. There was also transitional cell positivity for cyclin D1, a marker found in matrical cells of the human hair follicle. While pilomatrixoma occurs occasionally in the eyelid, the ossified eyelid variant in the current case is very rare, with only one preceding description in the literature.