Large Cell Calcifying Sertoli Cell Tumour: A Contemporary Multi-Institutional Case Series Highlighting the Diagnostic Utility of PRKAR1A Immunohistochemistry.

AIMS Large cell calcifying Sertoli cell tumour (LCCSCT) is a rare testicular sex cord-stromal tumour that primarily affects young patients and is associated with Carney complex. We sought to characterize the clinicopathological features of a series of LCCSCT and evaluate the diagnostic utility of PRKAR1A immunohistochemistry (IHC). METHODS AND RESULTS The LCCSCT cohort (n=15) had a median age of 16 years (range: 2-30 years). Four patients were known to have Carney complex. PRKAR1A IHC was performed in each case. For comparison, PRKAR1A IHC was also assessed in other sex cord-stromal tumours, including Sertoli cell tumour, not otherwise specified (SCT, NOS; n=10), intratubular large cell hyalinizing Sertoli cell tumour (n=1), and Leydig cell tumour (n=23). Loss of cytoplasmic PRKAR1A expression was observed in all but one LCCSCT (14/15; 93%). PRKAR1A expression was retained in all SCTs, NOS (10/10; 100%), the majority of Leydig cell tumours (22/23; 96%), and an intratubular large cell hyalinizing Sertoli cell tumour (1/1; 100%). One Leydig cell tumour showed equivocal staining (multifocal weak expression). CONCLUSIONS Overall, PRKAR1A loss is both sensitive (93%) and highly specific (97%) for the diagnosis of LCCSCT. PRKAR1A loss may aid its diagnosis, particularly in sporadic cases and those that are the first presentation of Carney complex.