Cytoplasmic accumulation of peanut agglutinin-binding glycoconjugates in the cells of primary melanoma correlates with clinical outcome

In an experimental model, human melanoma cell lines enriched for cells that express the glycoconjugate B-D galactose N-acetyl-D- galactosamine, which reacts with the peanut agglutinin lectin (PNA), are associated with an incr ease in the frequency of metastases. We previously showed that this glycoco njugate is expressed on the cells of some primary melanomas in humans and t hat such cells are found selectively in melanomas with a high risk for deve loping metastases and causing death. Using fixed archival tissues from 99 p rimary melanomas and lectin histochemistry, we found 65 tumors that contain ed melanoma cells that were PNA-positive. PNA-reactive cells were not ident ified in normal melanocytes or in the nevocytes of 24 nevi. PNA-reactive ma terial accumulates adjacent to the nucleus in the area of the Golgi apparat us, initially as a tiny dot, but later in quantities sufficient to displace and indent the nucleus, producing a signet ring cell-like appearance. Tumo r cells containing PNA-reactive material were associated with more evolved, deeper, and thicker tumors. Two melanomas up to Clark level II were PNA po sitive (20%), compared with 60% of level III, 76% of level IV, and 100% of level V. Five of 13 tumors less than 0.76 mm thick (39%) were positive, com pared with 50% of tumors 0.76 to 1.49 mm thick, 64% of tumors 1.5 to 2.99 m m thick, and 85% of tumors 3 mm thick or thicker. PNA-reactivity was negati vely correlated with disease-free survival (PNA-negative, 49.2 +/- 23 month s; PNA-positive grade 1, 41.6 +/- 26 months and PNA-positive grade 2, 24.4 +/- 23 months), survival rate 5 years after initial treatment (PNA-negative , 84.8%; PNA-positive grade 1, 63.8%; and PNA-positive grade 2, 31.3%) and disease-free survival at 5 years after initial treatment (PNA-negative, 69. 7%; PNA-positive grade 1, 53.2%; and PNA-positive grade 2, 25%). HUM PATHOL 30:556-561. Copyright (C) 1999 by W.B. Saunders Company.