Abstract
A 42-year-old male with a history of Type II Diabetes Mellitus and gout presented with slowly enlarging, painless nodular masses located behind his left ear. Clinical examination disclosed multiple well-circumscribed masses, suggestive of either calcification or lipid accumulation. Histologic examination revealed abundant acellular eosinophilic material within the dermis, with scattered aggregates of lymphocytes and plasma cells predominantly in the deep dermis. Congo red staining highlighted the acellular eosinophilic material, and kappa and lambda in situ hybridization demonstrated a lambda-restricted plasma cell population. These findings were consistent with nodular amyloidosis with a lambda-restricted plasma cell process. Serum Protein Electrophoresis (SPEP) revealed a polyclonal increase in IgA without monoclonal gammopathy, emphasizing the complexity of amyloidosis diagnosis and the necessity of assessing systemic risks. Although most cases of nodular amyloidosis remain confined to the skin, there is a 7% risk of progression to systemic amyloidosis. Histologically, the amyloid deposits are composed of light chain-derived AL protein, mirroring systemic amyloidosis. This case underscores the importance of clinical evaluation, pathological analysis, and SPEP in the diagnosis and management of nodular amyloidosis. It also illustrates the indistinguishable nature of a localized light chain-derived AL protein from systemic amyloidosis, highlighting the intricacies of this rare cutaneous condition.