Glypican-3 protein expression in primary and metastatic melanoma: a combined immunohistochemistry and immunocytochemistry study.
BACKGROUND
The incidence of melanoma is increasing. Fine-needle aspiration (FNA) is critical in documenting recurrent/metastatic disease in established cases. The potential of metastatic melanoma (MM) to mimic epithelial tumors presents a diagnostic dilemma. In liver FNA, the distinction between hepatocellular carcinoma (HCC) and MM is a frequent challenge. Glypican-3 (GPC3), a heparan sulfate proteoglycan, is a highly sensitive and specific marker for HCC. Serum GPC3 was shown to be expressed in 40% of primary melanomas (PMs), but to the authors' knowledge no tissue studies to date have assessed GPC3 expression in MM. In this study, GPC3 protein expression was investigated in FNAs from MM, and in corresponding histologic sections from the primary tumors.


METHODS
Sixty archival, direct FNA smears or CytoLyt-fixed samples from 50 patients with MM were retrieved together with formalin-fixed, paraffin-embedded specimens available from 17 corresponding PMs. All cases were stained with anti-GPC3 antibody. FNA and core biopsy specimens from HCCs and benign liver were used as positive and negative controls. GPC3 expression was divided into 2 categories: negative (negative or weak cytoplasmic staining) and positive (moderate or strong cytoplasmic with membranous accentuation).


RESULTS
All FNAs from MM cases were negative (0 of 60) for GPC3. The exact 95% Clopper-Pearson confidence interval was 0.0% to 5.96%. Only 1 case of PM (1 of 17; 5.9%) demonstrated weak focal cytoplasmic staining (regarded as negative).


CONCLUSIONS
In the current study, all MM and PM cases in archival FNAs and tissue sections were found to be negative for GPC3. These data suggest that GPC3 is not expressed in melanoma using the 1G12 clone.
Kandil
Dina
D
Department of Pathology, University of Vermont, Burlington, Vermont, USA. Dina.Kandil@umassmemorial.org
Leiman
Gladwyn
G
Allegretta
Mark
M
Evans
Mark
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044963:Biopsy, Fine-Needle; D005260:Female; D053673:Glypicans / Q000032:analysis*; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008545:Melanoma / Q000737:chemistry* / Q000556:secondary*; D008875:Middle Aged
D053673:Glypicans