Abstract

In the study, it was determined whether cytofluorometry of nuclear DNA contents and fluorescence microscopic findings of formalin-fixed paraffin-embedded unstained specimens and immunostaining of the same specimens with HMB-45 coud be used to differentiate amelanotic or melanotic Spitz nevus from amelanotic or melanotic nodular melanoma.
The mean of averaged nuclear DNA contents was 2.14±0.14C (2.00 to 2.39) in amelanotic Spitz nevus and 2.17±0.22C (1.96 to 2.62) in melanotic Spitz nevus, showing no significant difference between amelanotic and melanotic types. Histograms of nuclear DNA contents showed a diploid pattern in all cases of both amelanotic and melanotic types. The mean of averaged nuclear DNA contents was 3.64±0.52C (2.91 to 4.45) in amelanotic nodular melanoma and 3.22±0.55C (2.60 to 3.93) in melanotic nodular melanoma, showing no significant difference between the 2 types. Histograms disclosed an aneuploid pattern in all cases of nodular melanoma. The mean of averaged nuclear DNA contents in nodular melanoma was 3.43±0.56C, which was significantly higher, as compared with 2.16±0.18C seen in Spitz nevus (P<0.0001, Wilcoxon's test).
In terms of fluorescence microscopic findings of formalin-fixed paraffin-embedded unstained specimens and HMB-45 immunostaining, the junctional components of nodular melanoma showed fluorescence and strongly positive HMB-45. Although a portion of intraepidermal nests of spindle cells in Spitz nevus were composed of fluorescence-positive tumor cells, no fluorescence was observed in nests of epithelioid cell which were negative for HMB-45.
From these results, it was thought that precision of determination of benignancy or malignancy could be improved by a combination of cytofluorometry of nuclear DNA contents with fluorescence microscopic findings of formalin-fixed paraffin-embedded unstained specimens and HMB-45 immunostaining.