Comparison of histology and extracellular matrix between autoimmune and alcoholic chronic pancreatitis

In autoimmune chronic pancreatitis (AIP), the histology is known to be characteristic and histologic recovery including pancreatic fibrosis has been reported after steroid therapy. The aims of this study were to demonstrate whether these histologic findings were unique to AIP and evaluate any differences in the composition of extracellular matrix between AIP and ordinary chronic pancreatitis.

Histologic findings and extracellular matrix proteins (collagen types I, III, and IV and fibronectin) were evaluated in 15 patients with clinically proven AIP and compared with those of 8 patients with surgically treated alcoholic chronic pancreatitis (ACP).

The pattern of fibrosis was mainly loose fibrosis with stromal edema in AIP, while it was dense fibrosis in ACP. Acinar atrophy was more diffuse and severe in AIP than ACP. While diffuse with same stage of inflammatory activity was observed in AIP, multifocal inflammation with different stage of inflammatory was seen in ACP. For extracellular matrix proteins, dense deposition (compared with normal controls) of collagen type III was observed more frequently in ACP than AIP (P < 0.05). ACP showed decreased deposition of collagen type IV more frequently than AIP (P = 0.001).

Fibrosis and inflammation are common to both AIP and ACP, but the pattern is very different between the 2 groups, and the deposition of collagen types III and IV is substantially different between AIP and ACP.