Detection of GD3 ganglioside in primary melanomas depends on histopathologic procedures used for tumor preservation.

Gangliosides, cell surface glycosphingolipids, are implicated in diverse biologic functions potentially important for tumor growth. Because expression of the GD3 ganglioside may have an impact on the melanoma malignancy, and therefore on the patient prognosis, we evaluated the feasibility of a retrospective immunohistochemical study of GD3 in paraffin embedded biopsies of primary melanomas. Immunoperoxidase staining of frozen and deparaffinized sections of melanoma lesions with two anti-GD3 antibodies was compared using Dako biotin-streptavidin detection kit. Residual ganglioside content was evaluated in the tissues submitted to routine histopathologic procedures using HPLC. A strong and reproducible staining was obtained with both antibodies on frozen sections of all 17 melanoma samples. However, only KM641 antibody could detect GD3 on deparaffinized sections. Biochemical quantification revealed that the Bouin fixative resulted in degradation of GD3. Additionally, most of GD3 was eluted from the tissue samples during dehydration and re-hydration steps. A subgroup of tumors particularly rich in GD3 could be detected on deparaffinized sections after standard formaldehyde fixation. Clinical evolution of such melanomas can now be compared to the group with low GD3 expression. However, any Bouin-fixed, paraffin-embedded biopsies should be excluded from such a retrospective study.