Seminomas with exclusive intertubular growth: a report of 12 clinically and grossly inconspicuous tumors.

Intertubular growth in seminoma is characterized by seminoma cells, either singly or in small clusters, between preserved seminiferous tubules. It is a common, although focal, pattern in many seminomas where it is admixed with the usual sheet-like and nested arrangements and does not pose any diagnostic problems in such cases. We describe, in contrast, the clinicopathologic features of 12 cases with exclusively intertubular growth and which were typically diagnostically problematic. The 12 patients lacked overt clinical signs of a primary testicular mass. Three presented with infertility, 2 with cryptorchidism, 2 with metastases, 1 with pain and testicular atrophy, and the presentation was unknown in 4. On gross examination, no mass was apparent in 9 cases with available data, but ill-defined firm areas or foci of whitish-brown discoloration were occasionally noted. Microscopically, the process was characterized by individual, dispersed tumor cells or small clusters of cells growing between the seminiferous tubules. The tumor cells were often obscured by a lymphocytic infiltrate or, less commonly, nodules of hyperplastic Leydig cells. Common associated findings were tubular atrophy with sclerosis and thickening of tubular basement membranes and intratubular germ cell neoplasia, unclassified type. Immunostains against placental-like alkaline phosphatase and c-KIT (CD117) highlighted the seminoma cells in all cases examined. In pure form, intertubular seminoma is both clinically and pathologically inconspicuous and may be misdiagnosed as atrophy, scar, or orchitis.