EPITHELIAL MARKERS IN MALIGNANT-MELANOMA - A STUDY OF PRIMARY LESIONSAND THEIR METASTASES

In order to determine epithelial markers in malignant melanoma in rout inely processed paraffin sections and to compare the staining of prima ry (cutaneous) malignant melanomas and their metastases, we stained fo rmalin-fixed paraffin sections of 13 primary and 18 metastatic maligna nt melanomas using the streptavidin-biotin peroxidase method by antibo dies to S-100, vimentin, HMB-45, polyclonal carcinoembryonic antigen ( CEA), monoclonal CEA, cytokeratins (CAM 5.2 and broad-spectrum CKKES), and epithelial membrane antigen (EMA). All primary and most metastati c malignant melanomas showed positive staining with anti-S-100, HMB-45 , and anti-vimentin. Reactivity with polyclonal CEA was observed in 15 (48%) of the 31 lesions; 14 of them were metastatic. No lesion was re active with monoclonal CEA. Significant cytokeratin (CK) staining was evident in only three (9.7%) lesions (all metastatic), which also stai ned specifically with anti-CK 18. EMA was observed only focally in two (6.5%) lesions. There was no correlation between epithelial markers s taining of the primary tumours and their metastases. All lesions with CK or EMA staining showed concomitant extensive staining for S-100, HM B-45, and vimentin. We conclude that (a) polyclonal CEA staining in ma lignant melanoma is not rare and is probably due to CEA-related molecu les; (b) significant CK reactivity is rare and related to simple CK, s uch as CK 18; (c) epithelial marker reactivity is more common in metas tases of malignant melanomas and is not correlated to the reactivity i n their primary tumors. Considering our results and reports of positiv e S-100, vimentin, and HMB-45 in epithelial tumors, a wide panel of an tibodies is recommended for the study of undifferentiated tumors.