Answer: Spermatocytic seminoma

Histology: The lesion consists of a cellular tumor composed of loosely cohesive cells. At higher magnification, most of the cells contain medium size nuclei many with visible nucleoli. Occasionally smaller cells with more condensed nuclear chromatin are identified. In addition, scattered much larger cells are also noted. Numerous mitotic figures are visible. The cytoplasm of the cells in the current case is eosinophilic. The tumor extends in between seminiferous tubules. A striking feature of this case is the filling up of preexisting seminiferous tubules with tumor cells. The lesion lacks the following features: lymphocytic infiltrate, associated granulomatous inflammation, and associated syncytiotrophoblastic giants cells.

Discussion: A feature seen in the current case that may be confusing is the extension of tumor cells in between seminiferous tubules rather than completely replacing seminiferous tubules. Characteristically, we associate this finding with hematopoietic tumors especially leukemia. None-the-less, occasionally one may see this both with ordinary and spermatocytic seminoma. In contrast to large cell lymphoma, which is the most common testicular tumor seen in older individuals, the majority of cells in the current case lack vesicular nuclei with prominent nucleoli. Rather, most of the nuclei have a very fine delicate chromatin appearance. One could also rule out lymphoma readily with the use of various lymphoid markers that would be negative in spermatocytic seminoma.

Classic seminomas consist of sheets of cells with abundant clear cytoplasm reflecting a high glycogen content. The nuclei in classic seminomas are uniform and round, typically with large sometimes multiple eosinophilic nucleoli. In approximately 80% of classic seminomas, one would see a lymphocytic infiltrate. Other findings often seen in classic seminomas include syncytiotrophoblastic giant cells, granulomatous inflammation or an admixture of other germ cell tumor types. In spermatocytic seminomas, all of these features are lacking. Also, with classic seminoma, one frequently sees intratubular germ cell neoplasia. This case demonstrates one of the nicest examples that I have seen of intratubular growth of spermatocytic seminoma. With this process, preexisting seminiferous tubules are filled with the same morphology of three cell-types as seen in the infiltrating component of spermatocytic seminoma. In contrast, intratubular germ cell neoplasia seen with classic seminoma consists of cells with large nuclei, prominent nucleoli and clear cytoplasm often as a single cell layer up against the seminiferous tubule basement membrane. Whereas cells of intratubular germ cell neoplasia are positive with stains for placental alkaline phosphatase (PLAP), they are negative in spermatocytic seminoma. A variant of classic seminoma has been called anaplastic seminoma or synonymously high mitotic rate seminoma. These are merely cases of classic seminoma with either very high mitotic activity or in some cases a greater degree of pleomorphism. We do not use this designation as it has been shown not to be of prognostic or therapeutic significance. Spermatocytic seminomas are entirely benign and do not need adjuvant radiotherapy as is often administered with classic seminoma. The only caveat to their entirely benign course is that rarely spermatocytic seminomas may present with a co-existing sarcomatous component which worsens the prognosis. However, if a patient has a spermatocytic seminoma without sarcoma at presentation, there is no risk that a sarcoma will develop at a later time.