Abdominal subcutaneous fat pad aspiration and bone marrow examination for the diagnosis of AL amyloidosis: the reliability of immunohistochemistry.

Tissue biopsy is essential for the diagnosis and typing of amyloidosis. Given its safety and ease, abdominal fat pad (AFP) is the first biopsy site of choice; bone marrow (BM) biopsy should additionally be performed to identify underlying plasma cell dyscrasia. The aim of the present study was to assess the usefulness of combined biopsy and immunohistochemical staining of AFP and BM tissues for the diagnosis and typing of amyloidosis. A total of 65 patients were examined. Congo red staining and immunohistochemical staining with antibodies were performed. Of 51 patients with systemic amyloidosis, 50 patients were examined with fat pad aspirates and 38 (76 %) cases were positive. All 51 patients were also examined by BM analysis and 25 (49 %) cases were positive. Including both AFP aspirates and BM specimens, 90 % of patients with systemic amyloidosis were Congo red positive. Of the 49 patients with AL amyloidosis, immunohistochemical stains were positive in 67.6 % of patients with AFP aspirates and in 50 % with BM specimens. Combining AFP aspirate and BM examination, immunohistochemical stains yielded positive stains for the corresponding circulating monoclonal immunoglobulin in 72.7 % of cases, and hence these analyses appear to be valuable in diagnosing the type of amyloidosis.