BAP1: case report and insight into a novel tumor suppressor.

Background: BRCA1-Associated-Protein 1 (BAP1) is a dynamic tumor suppressor which, when mutated, has been associated with an increased risk of uveal melanoma, cutaneous melanoma, mesothelioma, and several other cancers. Germline BAP1 mutations have been extensively studied, where they have been found to cause hereditary cancer susceptibility. However, their sporadic counterparts, tumors that display a loss of BAP1 expression due to somatically arising mutations in the BAP1 gene, remain a poorly described entity.

Case presentation: Here we present the case of a 49-year-old female who presented with an asymptomatic dome-shaped pink papule on the dorsal foot which was found on biopsy to be deficient in the BAP1 tumor suppressor. While the patient's family history did not suggest the presence of a familial cancer syndrome, germline genetic testing was performed and was negative. The patient underwent surgical excision of this sporadically appearing "BAPoma" by Mohs surgery.

Conclusions: Given the relatively banal clinical appearance of these dome-shaped neoplasms, sporadic BAPomas may often be overlooked by clinicians and dermatologists. In addition to providing a representative case, here we also provide a synopsis of the current understanding of these neoplasms, both in terms of the histopathological features, as well as the molecular mechanisms underlying BAP1 function and its ability to prevent tumorigenesis.