Pathologists' integration of prior biopsies of women with germline PTEN mutations may expedite the identification of this rare cancer predisposition syndrome.

PTEN hamartoma tumour syndrome (PHTS) is a rare cancer predisposition syndrome, caused chiefly by pathogenic and likely pathogenic (P/LP) variants in in the PTEN gene. Carriers have substantially elevated risks of various malignancies and develop benign lesions in multiple organ systems. The rarity of this disease, the decades-long unfolding of its clinical features, involvement of multiple sites and the absence of distinguishing features of each lesion hamper the identification of this condition, limiting opportunities for screening of affected individuals and their families. Given laboratory information systems are the repositories of patients' biopsies, we are interested in whether PHTS patients' prior biopsies may serve as clues to the possibility of this syndrome. With ethics committee approval, through a collaboration amongst our state-wide Adult Genetics Unit and all pathology laboratories in our state, we have undertaken a 28-year longitudinal survey (1990-2018) of the biopsy histories of 12 women known to have P/LP PTEN variants. Only one woman had a family history of Cowden syndrome, with the remaining 11 patients' mutations being discovered later. The earliest biopsy was at age 19. The most common finding was the development of multiple benign mucocutaneous lesions, with 10 women presenting with these, including a range of benign vascular lesions (eight patients), various fibromatous lesions of the skin and mucosal sites (six patients), a ganglioneuroma and a juvenile polyp. Ten women developed breast cancer, only four before the age of 40. Seven women developed a second breast cancer, two synchronously and five at intervals of 3-11 years. Other neoplasms included endometrial carcinoma (two patients) and dysplastic cerebellar gangliocytoma (three patients). Integrating the biopsy histories of PTEN P/LP variant carriers over time may assist in raising the possibility of an underlying cancer susceptibility syndrome, so appropriate clinical and genetic counselling and evaluation may be considered.