Cutaneous Basal Cell Carcinoma In Situ: A Review of the World Literature.

Cutaneous basal cell carcinoma (BCC) in situ is a recently recognized subtype of the skin neoplasm in which the abnormal cells are confined to the epidermis. BCC in situ of the skin was previously referred to as a superficial BCC. A review of the world literature has revealed 10 cutaneous BCCs in situ that have been described in nine patients but likely reflect a more general phenomenon. The neoplasm typically presents as an asymptomatic red plaque on the abdomen, upper extremity, back, and chest. Pathologic changes frequently show confluent tumor cells along the epidermal basal layer or superficial aggregates of neoplastic cells that are contiguous with the epidermis and extend into the dermis. Genomic evaluation has been performed in neoplasms from one individual with cutaneous BCC in situ and metastatic BCC; like other variants of BCC, an aberration of the gene was observed. In contrast to his liver metastasis, the in situ carcinoma had a lower tumor mutational burden, lacked programmed death-ligand 1 and programmed death-ligand 2 amplification and had a distinct mutation, suggesting that the in situ BCC of his skin and the metastatic BCC of his liver were derived from different clones of cells.