“BURNT-OUT” TESTICULAR GERM CELL TUMORS

Abstract

Infrequently males are found to have extragonadal germ cell neoplasms without testicular symptoms or clinical evidence of a primary testicular tumor. Germ cell tumors arising in the mediastinum or pineal region without clinical evidence of a testicular primary are likely to represent primary extragonadal germ cell tumors arising in misplaced germ cells. However, there is considerable evidence that retroperitoneal germ cell tumors arising in the absence of a clinically evident testicular neoplasm are less likely to have arisen primarily at that site, and are more likely to represent metastases from a regressed (burnt-out) primary testicular germ cell tumor.1 The phenomenon of spontaneous primary germ cell tumor regression in a setting of metastatic cancer was documented in an autopsy study several decades ago.2 The probability of this occurrence appears roughly to parallel the tendency of an individual tumor type to undergo necrosis; consequently, choriocarcinoma is most likely to burn out followed in frequency by embryonal carcinoma and mixed germ cell tumors. Regression is uncommon with testicular seminoma and probably does not occur in teratoma, a neoplasm that seems resistant to spontaneous necrosis as well as being resistant to therapy induced necrosis. In a setting of known retroperitoneal germ cell tumor with palpably normal testes ultrasound may be helpful in detecting the presence of a subtle mass lesion. Examination of orchiectomy specimens may disclose no apparent gross abnormalities or may demonstrate the presence of scarring, which may be ill-defined and poorly demarcated, or may be circumscribed and relatively easy to identify in the background of normal adjacent tissue (fig. 1). Small cysts or small hard cartilaginous nodules may be evident, reflecting the presence of zones of residual teratoma. Microscopically, the testicular germ cell neoplasm may be entirely or partially burnt-out. In the former case the zone of complete regression is represented by a residual deposit of collagen that typically is infiltrated by hemosiderin laden macrophages, scant lymphocytes and lipid laden macrophages (fig. 2). Intratubular germ cell neoplasia may be evident in the surrounding testicular parenchyma. Dystrophic calcification and necrotic material may be seen within the zone of scarring, arrayed in such a way as to suggest necrotic intratubular germ cell tumor. In cases of incomplete regression small foci of residual invasive germ cell tumor are present, most commonly of teratomatous type. Residual germ cell tumor in the testis may be histologically different from the metastatic cancer. This may reflect selective regression of only discrete elements of a primary testicular mixed germ cell tumor; alternatively, it may reflect transformation of tumor types in the metastatic malignancy.