Incidence and Pitfalls of Intratesticular Adipose Tissue Encountered in Orchiectomy Specimens.

Based on the eighth edition of the American Joint Committee on Cancer staging system, postpubertal germ cell tumors (GCT) and malignant sex cord-stromal tumors (SCST) of the testis invading hilar soft tissue are of pathologic stage pT2. Adipose tissue is typically used as an anatomical landmark by pathologists for determining hilar soft tissue invasion. Herein, we evaluated for the presence, location, and extent of intratesticular fat in a multi-institutional cohort of orchiectomies. Consecutive orchiectomies from 3 academic institutions were reviewed (n = 605), including both benign and malignant specimens. Intratesticular fat was identified by hematoxylin and eosin (H&E) evaluation in 11/605 (1.8%) orchiectomies, including the following diagnoses: mixed non-teratomatous GCT (n = 1), mixed GCT with a teratoma component (n = 2), pure teratoma (n = 2), Leydig cell hyperplasia (n = 1), regressed GCT (n = 1), hormone therapy effect (n = 1), atrophic changes (n = 1), fibrosis (n = 1), infarction (n = 1). Adipose tissue was located within the rete testis stroma (n = 2), just below the rete testis (n = 4), within nodules of Leydig hyperplasia between the seminiferous tubules (n = 1), or within the confines of testicular parenchyma (n = 4). Among the 4 specimens containing admixed neoplastic (teratomatous) fat, the extent of adipose tissue ranged from 3.0 to 11.0 mm (mean 6.8 mm). Among the 7 specimens with non-neoplastic adipose tissue within/near the rete, the extent ranged from 0.1 to 12.7 mm (mean 2.3 mm). Although uncommon, intratesticular fat can be found in orchiectomy specimens, which may represent a staging pitfall in GCT and SCST especially when located at the interface between the testicular parenchyma and hilum.