Anderson, William J.

Abstract Spermatocytic tumor (ST) is a rare type of germ cell tumor that occurs exclusively in the postpubertal testis and typically affects elderly men. Most STs are benign, but rare cases exhibit aggressive clinical behavior, often in association with transition to sarcomatoid histology. Limited molecular analyses have been performed on STs; therefore, their genomic and epigenomic features remain incompletely described. Twenty‐seven samples from 25 individual patients were analyzed with a combination of DNA sequencing panels, genomic methylation profiling, SNP array, isochromosome (12p) [i(12p)] FISH, and immunohistochemistry. The series included five metastasizing tumors (three with sarcomatoid transformation, one anaplastic, and one conventional) and 20 non‐metastasizing tumors (14 anaplastic and six conventional). Anaplastic tumors comprised a monomorphic population of intermediate‐sized neoplastic cells, as previously described. Multiomic analyses demonstrated that there were two genomic subgroups of STs: one with diploid genomes and hotspot RAS / RAF variants and the other with global ploidy shift and absence of recurrent mutations. Relative gain of chromosome 9 was a consistent finding in both subgroups. A comparison of metastasizing and non‐metastasizing cases demonstrated that aggressive behavior was associated with the acquisition of pathogenic TP53 mutations and/or relative gains of 12p/i(12p). In cases with sarcomatoid transformation, TP53 mutations seem to underlie the transition to sarcomatoid histology. Genomic methylation analysis demonstrated that aggressive cases with gains of 12p cluster closer to pure seminomas than to STs without gains of 12p. In conclusion, STs include two genomic subgroups, characterized by global ploidy shifts without recurrent mutations and diploid genomes with RAS / RAF hotspot mutations, respectively. Biologic progression was associated with relative gains of 12p and TP53 mutations. The findings in STs with relative gains of 12p suggest that they may exhibit biologic characteristics akin to those seen in germ cell neoplasia in situ ‐related germ cell tumors rather than non‐germ cell neoplasia in situ ‐derived STs. © 2023 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

AimsLarge 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 characterise the clinicopathological features of a series of LCCSCT and evaluate the diagnostic utility of PRKAR1A immunohistochemistry (IHC).Methods and resultsThe 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 hyalinising Sertoli cell tumour (n = 1) and Leydig cell tumour (n = 23). Loss of cytoplasmic PRKAR1A expression was observed in all but one LCCSCT (14 of 15; 93%). PRKAR1A expression was retained in all SCTs, NOS (10 of 10; 100%), the majority of Leydig cell tumours (22 of 23; 96%) and an intratubular large cell hyalinising Sertoli cell tumour (1 of 1; 100%). One Leydig cell tumour showed equivocal staining (multifocal weak expression).ConclusionsOverall, 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.