Extragonadal germ cell tumors: a fine-needle aspiration biopsy study.

Germ cell tumors (GCT) are neoplasms that originate predominately in the ovary and testis. Tumors of germ cell origin only very uncommonly arise in extragonadal sites. We have diagnosed ten primary malignant extragonadal GCT arising in the mediastinum, retroperitoneum, liver, and sacrococcygeal region by fine-needle aspiration biopsy (FNAB). Patient ages ranged from 1 to 54 years; the majority were males. Our series included three seminomas, three yolk sac tumors (YST), one choriocarcinoma, one embryonal carcinoma, and two mixed, poorly differentiated GCT. In aspirates, seminomatous elements are dissociated with uniform mononucleate cells having large vesicular nuclei and prominent nucleoli. A tigroid background is produced with Diff-Quik-stained smears. YST yields cohesive clusters of cells with large nuclei, vacuolated cytoplasm, and extracellular hyaline matrix (spheres or hyaline globules). Giant multinucleate tumor cells are seen in choriocarcinoma. Embryonal carcinoma yields cellular smears of hyperchromatic cells with scant cytoplasm arranged predominantly in glandular or papillary formations. Ultrastructural (four cases) and immunocytochemical (seven cases) studies of aspirated material corroborated our cytologic interpretations. Aneuploid tumor cells were found by flow cytometry in aspirated material from a YST. Subsequent histologic examinations were performed on eight, and all were confirmatory. Although extragonadal GCT are relatively uncommon, they need to be considered in FNAB material from midline mass lesions. Ancillary studies were useful in confirming their diagnosis.