Diagnostic value of markers M2A, OCT3/4, AP-2γ, PLAP and c-KIT in the detection of extragonadal seminomas

Aims: To compare the suitability of new seminoma markers including transcription factors AP-2 gamma, OCT3/4 and M2A for detection of metastatic and extragonadal seminomas with the two well-known markers c-KIT and PLAP. Materials and methods: The immunohistochemical distribution of PLAP, c-KIT, M2A, AP-2 gamma and OCT3/4 was examined in two pineal germinomas, 28 metastatic seminomas and 10 of their testicular primaries. Evaluation of specificity was achieved by additional tissue array studies on 75 malignancies other than germ cell tumours (GCT). Clinical data including serum PLAP were available in 18 patients. Results: Compared with other markers, significantly better staining results were observed with antibodies to M2A and AP-2 gamma in all seminomatous GCT. In contrast, the staining pattern with antibodies to c-KIT, PLAP and OCT3/4 was variable or absent. The lowest specificity was obtained with c-KIT, which was expressed in a variety of non-GCT. The only M2A+ mesothelioma expressed no other seminoma markers. No correlation between serum PLAP level and tissue PLAP expression was found. Conclusions: M2A and AP-2 gamma are the most sensitive markers for seminoma metastases or primary extragonadal seminomas. Combination of these markers provides highly specific and clear results for detection of a seminomatous GCT.