The clinical lesions may resemble pemphigus, pemphigoid, erythema multiforme, graft-vs.-host disease, or lichen planus. A common denominator in all patients is the concomitant occurrence of either occult or confirmed systemic neoplasm. It is imperative to confirm the diagnosis through microscopy, where intraepidermal suprabasal cleavage, epidermal acantholysis, dyskeratotic keratinocytes and vacuolar changes in the basal epidermis, interfacial dermatitis, and epidermal exocytosis can be seen. Furthermore, the deposition of immunoglobulin G (IgG) and complement in the epidermal intercellular spaces, detected by direct and/or indirect immunofluorescence, is equally crucial for confirming the diagnosis.
Paraneoplastic pemphigus is the term used for an exclusive subset of pemphigus.