Testicular germ cell tumours. Current problems of histogenesis and classification

Protein overexpression and gene amplification of epidermal growth factor receptor in adult testicular germ cell tumors: potential role in tumor progression

Little is known about the pathologic significance of epidermal growth factor receptor (EGFR) expression in malignant testicular germ cell tumors (TGCTs) in adults. From the primary tumor sites of a cohort of 110 TGCT cases, we obtained 209 histologically distinct components: 53 intratubular germ cell neoplasia unclassified (IGCNU) lesions, 83 seminomas (66 pure-form seminomas and 17 seminoma components in the mixed-form with nonseminomatous TGCTs), 27 embryonal carcinomas, eight choriocarcinomas, 18 yolk sac tumors, and 20 immature teratomas. Samples were analyzed for expression of EGFR protein and EGFR gene amplification by immunohistochemistry and fluorescence in situ hybridization (FISH), respectively. Overexpression of the EGFR protein was detected in 28% of seminomas (27% in the pure-form and 29% in the mixed-form), 11% of embryonal carcinomas, 88% of choriocarcinomas, 44% of yolk sac tumors, and none of the IGCNU lesions or immature teratomas. A higher copy number (≥4 copies per cell) and amplification of the EGFR gene were detected in 20% and 10% of seminomas, 13% and 0% of embryonal carcinomas, 71% and 60% of choriocarcinomas, 15% and 8% of yolk sac tumors, and none of the IGCNU lesions or immature teratomas, respectively. Both higher copy number and amplification of the EGFR gene were positively correlated with immunohistochemical overexpression of EGFR protein (each P < 0.0001). These results suggest that overexpression of EGFR protein and increased copy number or amplification of the EGFR gene occur relatively frequently in primary TGCTs, and may play roles in the formation of invasive cancer and in the progression, especially morphological evolution, of tumors.

Allelic losses in carcinoma in situ and testicular germ cell tumours of adolescents and adults: evidence suggestive of the linear progression model

Testicular germ cell tumours (TGCTs) may arise through a process of multi-step carcinogenesis, and loss of heterozygosity (LOH) at specific loci is likely to be an important early event, although this has not been studied in detail. In order to explore the pathogenetic relationships among TGCTs, we investigated the genetic changes in testicular tumours that exhibit a disease continuum through the precursor carcinoma in situ (CIS) to either seminoma (SE) and/or non-seminomatous germ cell tumour (NSGCT). Universal amplification has been performed on 87 TGCT specimens and 36 samples of CIS cells microdissected from single paraffin-embedded tumour sections from 40 patients, including multiple specimens of CIS and TGCT cells of varied histology microdissected from 24 individual patients. Seventy-seven microsatellite markers were used to assay these samples for LOH at candidate regions selected from the literature, mapping to 3q, 5q, 9p, 11p, 11q, 12q, 17p and 18q. Construction of deletion maps for each of these regions identified common sites of deletion at 3q27-q28, 5q31, 5q34-q35, 9p22-p21 and 12q22, which correlate with allelic losses we have also observed in the precursor CIS cells. Evidence for allelic loss at 3q27-q28 was observed in all of the embryonal carcinoma samples analysed. We conclude that inactivation of gene(s) within these regions are likely to be early events in the development and progression of TGCTs. These results also provide molecular evidence in support of the hypothesis that SE is an intermediate stage of development within a single neoplastic pathway of progression from CIS precursor cells to NSGCT.

Immunohistochemical comparison between anaplastic seminoma and typical seminoma

In order to study the possible biological differences between anaplastic and typical seminoma, the following factors were studied in 11 cases of anaplastic seminoma and 15 cases of typical seminoma: mitotic activity, proliferating cell nuclear antigen (PCNA) expression, immunohistochemical analyses for cytokeratin, vimentin, placental alkaline phosphatase (PLAP), beta-human chorionic gonadotropin (beta-hCG), alpha-fetoprotein (AFP) and c-myc oncoprotein. Anaplastic seminoma was classified according to Mostofi's criteria, which is primarily based on the mitotic activity of the tumor. Mitotic activity was evaluated by both mitotic count and rate. Statistically significant correlations were observed between mitotic count and mitotic rate (R = 0.891), and between the mitotic count and PCNA labeling index (R = 0.792), in both typical and anaplastic seminomas. Immunostaining patterns for cytokeratin, vimentin, PLAP, beta-hCG, AFP and c-myc oncoprotein were not significantly different between typical and anaplastic seminoma. The present data indicated that no apparent clinicopathologic and immunohistochemical parameters discerning anaplastic seminoma from typical seminoma were present, when identifying anaplastic seminoma on the basis of high mitotic count. Anaplastic seminoma may therefore simply represent seminoma with high proliferative activity.

Seminoma testis with elevated serum beta-HCG--a category of germ-cell cancer between seminoma and nonseminoma

Serum beta-HCG was elevated in 10 of 83 consecutive patients with histologically pure seminoma (12%). Six patients with diagnostic stage I were successfully treated by radiation therapy. One patient with state IIc suffered a mediastinal relapse following retroperitoneal radiotherapy. Two other patients with high tumour burden achieved complete remission after induction chemotherapy followed by surgery and radiotherapy, respectively. One patient with retroperitoneal bulky disease reached permanent complete remission after radiation therapy alone. Beta-HCG-positive seminomas constitute a distinct category of germ-cell tumours on the basis of morphological and clinical features. Corresponding to the intermediate histological position between seminoma and nonseminoma, safe treatment of beta-HCG-positive seminoma can be achieved by radiotherapy in stage I, by retroperitoneal lymphadenectomy plus adjuvant chemotherapy in stages IIa, b and by induction chemotherapy in stages IIc and III.