This tumour is composed of primitive anaplastic epithelial cells that resemble early embryonic cells. It is the second most common histologic type of testicular tumour after seminoma.
Peak incidence is in the 20 to 30 year, age group.
Embryonal carcinoma is often smaller than seminoma at the time of presentation but tends to be more aggressive in behavior, although developments of chemotherapy have improved the prognosis considerably.
Grossly, lesions may be small and confined to the testis, but most examples are poorly demarcated, gray-white masses punctuated by foci of hemorrhage, necrosis, or both.
They may extend through the tunica albuginea into epididymis or spermatic cord.
Microscopically, they are composed of primitive epithelial cells with indistinct cell borders, prominent nucleoli and coarse chromatin. The cells form irregular sheets, tubules, alveoli and papillary structures. Mitotic figures and neoplastic giant cells are common.
Histochemically, syncitial cells are positive for HCG and AFP may be detected, and when present, indicates a mixed germ cell tumour with concomitant trophoblastic or yolk sac differentiation.