Examination of hematoxylin-eosin–stained sections demonstrated dermal deposits of amyloid and an admixture of plasma cells. The Congo red stain demonstrated the characteristic apple green birefringence on polarization.
PLCNA is the rarest form of amyloidosis.1 It is regarded as an extramedullary plasmacytoma, in which plasma cells localized to the skin generate light-chain immunoglobulins that degenerate to yield amyloid.2 The mean age at onset of PLCNA is 65 years, and the disease is twice as common in males as in females.2 Lesions are more often multiple than single, involving the legs more commonly than elsewhere on the body. The nodules, which resemble those seen in primary systemic amyloidosis, present as shiny masses with an amber hue and a waxy appearance. Superficial telangiectasias may be present.