A localized variant of paraneoplastic pemphigus: acantholysis associated with malignant melanoma

We report a 72-year-old male patient with a nodular malignant melanoma that was associated with focal suprabasal acantholysis (FSA). This phenomenon, which is regarded as an incidental finding by dermatopathologists, may be associated with inflammatory and also neoplastic skin diseases. Haematoxylin and eosin stained sections from an erythematous plaque surrounding the patient's tumour showed FSA, direct immunofluorescence (DIF) and indirect immunofluorescence (IIF) on normal human skin, monkey oesophagus and rat urinary bladder were negative. On electron microscopy few desmosomes could be detected in the basal cell layer of the acantholytic areas and there was a nearly complete loss of these structures in the spinous cell layer. Only remnants of cytoplasmic plaques and keratin filaments could be observed in those areas. In contrast, adherens junctions appeared to be well preserved. An enzyme-linked immunosorbent assay (ELISA) using recombinant fusion proteins as antigens did not show circulating autoantibodies against desmoglein 1 (Dsg1) or desmoglein 3 (Dsg3). In contrast, immunoblotting revealed autoantibodies directed against keratinocyte antigens with a molecular weight of 85 kDa and 250 kDa, the first band corresponding to the molecular weight of comigrating plakoglobin. Immunoprecipitation with patient serum also revealed a 85-kDa band. We conclude that these autoantibodies, probably in conjunction with cofactors produced by the tumour, could play a part in the pathogenesis of this variant of FSA, for which we propose the term 'localized paraneoplastic pemphigus.'