Bile duct–like differentiation in teratoma: a clinicopathologic and immunohistochemical study

Mediastinal Germ Cell Tumors: A Review and Update on Pathologic, Clinical, and Molecular Features

Mediastinal germ cell tumors (MGCTs) are the most common extragonadal germ cell tumors (GCTs) and most often arise in the anterior mediastinum with a male predilection. MGCTs also have a predilection for patients with Klinefelter syndrome and possibly other genetic conditions. MGCTs, as GCTs at other extragonadal sites, are thought to arise from germ cells improperly retained during migration along the midline during embryogenesis. Similar to their counterparts in the testes, MGCTs are classified into seminomatous and nonseminomatous GCTs. Seminomatous MGCT represents pure seminoma, whereas nonseminomatous MGCTs encompass pure yolk sac tumors, embryonal carcinoma, choriocarcinoma, mature or immature teratoma, and mixed GCTs with any combination of GCT types, including seminoma. Somatic-type or hematologic malignancies can also occur in association with a primary MGCT. MGCTs share molecular findings with GCTs at other sites, most commonly the presence of chromosome 12p gains and isochromosome i(12p). Treatment includes neoadjuvant chemotherapy followed by surgical resection of residual tumor, with the exception of benign teratomas, which require only surgical resection without chemotherapy. In this review, we highlight and provide an update on pathologic, clinical, and molecular features of MGCTs. Immunohistochemical profiles of each tumor type, as well as differential diagnostic considerations, are discussed.

Prostatic tissue in testicular teratoma. A clinicopathologic and immunohistochemical study

The presence of prostatic differentiation as part of teratoma is very unusual and has been reported less than 20 times in the literature; however, all but 1 case were described in ovarian teratomas. We reviewed 45 specimens of germ cell tumors with teratoma component in postpuberal male patients. Original hematoxylin and eosin review failed to identify glands morphologically consistent with prostatic differentiation. Immunohistochemical stains performed on 10 specimens from 10 patients with small glandular and/or tubular structures revealed 1 case with glands positive for prostatic-specific antigen, prostatic-specific acid phosphatase, and prostein/P501S, whereas high-molecular-weight cytokeratin and p63 highlighted only basal cells. The glands were irregular in size and shape and contained mostly cuboidal to columnar luminal-type cells with occasional basal-type cells. Re-review of all the specimens revealed a second block from the same testis as well as 1 retroperitoneal lymph node with metastatic teratoma in the same patient, also immunohistochemically confirmed. These glands were seen in a smooth muscle stromal background, adjacent to classic gastrointestinal and tracheobronchial teratoma components. Our findings show immunohistochemically confirmed prostatic differentiation in 2 specimens from 1 patient with teratoma. This study raises the possibility that prostatic differentiation, difficult to recognize on morphology alone, might not be that unusual and that immunostains can help detect it over the several different epithelial components of teratoma.