Hepatic amyloidosis. A histopathologic analysis of primary (AL) and secondary (AA) forms.

The liver is a major site of amyloid deposition. The spectrum of histopathologic changes in the liver was studied in 38 patients with systemic amyloidosis (25 with primary or myeloma-associated amyloidosis [AL] and 13 with secondary, reactive [AA] amyloidosis). Overall architectural distortion, alterations of portal triads, as well as predilection for topographic deposition in the parenchyma and/or blood vessel walls were noted. Significant histopathologic differences in AL or AA amyloid liver involvement included 1) portal fibrosis, seen in 7 of 25 (28%) AL patients and 8 of 13 (62%) AA patients (P = 0.05), 2) parenchymal amyloid deposition in 25 of 25 (100%) AL amyloid and 10 of 13 (77%) AA amyloid patients (P = 0.04), and 3) vascular amyloid deposition found in 17 of 25 (68%) with AL amyloid and 13 of 13 (100%) patients with AA amyloid (P = 0.02). These data vary from the widely held concept that deposition of amyloid is predominantly vascular in the AL form and parenchymal in amyloid AA. Clearly, however, in individual cases significant overlap occurred, and characterization of amyloid types based on morphologic distribution of amyloid deposits may be possible in only a minority of cases. In most cases, differentiation of amyloid AL and amyloid AA forms requires clinical, histochemical, immunochemical, and sometimes more elaborate laboratory amino acid sequence studies for accurate identification.