FLUORESCENCE IN-SITU HYBRIDIZATION ON NUCLEI FROM PARAFFIN-EMBEDDED TISSUE IN LOW STAGE PURE EMBRYONAL CARCINOMA OF THE TESTIS

Approximately 30% of patients who present with clinical stage A nonsem inomatous testis cancer are in fact pathologic stage B. In previous st udies an increasing volume of embryonal carcinoma in the orchiectomy s pecimen was associated with a higher likelihood of being pathologic st age B. However, not all patients with pure embryonal carcinoma in the primary tumor were pathologic stage B. In an effort to discriminate pa tients with pure embryonal carcinoma in the testicular specimen relati ve to pathologic stage, archival specimens from patients presenting wi th clinical stage A pure embryonal carcinoma were examined by fluoresc ence in situ hybridization (FISH) with newly developed probes for chro mosome arms 12p and 12q, Whole nuclei from archival material from 14 p atients (six pathologic stage A, seven pathologic stage B and one stag e C) with 100% embryonal carcinoma in the orchiectomy specimen were st udied using bicolor FISH with chromosome arm 12p- and 12q-specific pai nting probes developed by chromosome microdissection. In all cases a b linded analysis showed distinct regions of 12p and 12q probe hybridiza tion simultaneously and allowed identification of probable normal chro mosomes 12, as well as regions of amplification of 12p sequences, incl uding possible i(12p). In 5/14 specimens, a distinct and peculiar patt ern of 12p hybridization was observed which resembled 12p ''disarray'' or ''multifocal 12p''. Of the five specimens demonstrating multifocal 12p, four were pathologic stage B, while one was pathologic stage A, Whether the trend toward multifocal 12p predicts metastatic potential in primary testicular embryonal carcinoma will need to be assessed usi ng a larger series of patients.