Answer: Seminoma

Histology: There is approximately a 7 mm area within the testis which consists of increased cellularity between seminiferous tubules showing a Sertoli cell only pattern and peritubular sclerosis. The cellular component between the seminiferous tubules consists of lymphocytes admixed with large cells showing the typical nuclear and cytoplasmic features of seminoma cells. These consist of enlarged nuclei with prominent nucleoli which are fairly uniform one cell to another. The cells have abundant clear cytoplasm. Admixed with the seminoma cells are Leydig cells which have rounder, smaller nuclei with a single central prominent nucleolus and abundant eosinophilic cytoplasm.

Discussion: This case is relatively uncommon, consisting of a seminoma that is exclusively intertubular. Rather than growing as an invasive mass which has displaced and destroyed seminiferous tubules, this case is more subtle with only scattered seminoma cells in between preserved seminiferous tubules. If one had questions regarding the diagnosis, one could stain these cells with PLAP or c-Kit, which would highlight the seminoma cells. A recent study highlighted this phenomenon.

Reference(s):
– Am J Surg Pathol 28:1163-8,2004.