Histopathological and immunohistochemical study of amyloidosis cutis nodularis atrophicans--comparison with systemic amyloidosis.

Three cases of amyloidosis cutis nodularis atrophicans (ACNA) were investigated histologically and immunohistochemically to determine the nature and origin of the deposited amyloid. A pulmonary lesion from a case of nodular pulmonary amyloidosis, and cutaneous lesions from three cases of primary systemic amyloidosis, two cases of secondary systemic amyloidosis and three cases of secondary cutaneous amyloidosis following basal cell epithelioma were also examined for comparison. Histology showed infiltration of numerous plasma cells adjacent to amyloid deposits in ACNA and nodular pulmonary amyloidosis, but not in systemic amyloidosis. Immunohistochemically, the cytoplasm of the plasma cells was stained with anti-immunoglobulin light chain or anti-Bence-Jones protein antisera or both, and amyloid material stained with anti-AL antiserum in ACNA and nodular pulmonary amyloidosis. These results suggest that, in ACNA, the plasma cells may produce and secrete immunoglobulin light chains or Bence-Jones protein or both, which undergo proteolysis to protein AL or amyloid fibril proteins which have the same immunoglobulin determinants as protein AL. The product is then deposited locally to form nodules in the dermis.