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.