Ultrastructure of syncytiotrophoblast-like cells in seminomas of the testis.

An ultrastructural examination of five syncytiotrophoblast-like cells (STLC) from three otherwise pure seminomas was performed. All five STLC demonstrated ultrastructural features identical to those of normal syncytiotrophoblastic cells. The STLC were surrounded by sinusoidal spaces and cells whose ultrastructure was compatible with that of seminoma cells, though the presence of cytotrophoblastic cells cannot be excluded with certainty. We conclude that STLC in seminomas are indeed syncytiotrophoblastic and their genesis remains an enigma.