肝臓の奇異なる腫瘍"血管筋脂肪腫":病理組織学的分類と増生パターンについて

Abstract

Primary hepatic angiomyolipoma (AML), 39 tumors found in 31 patients, were analyzed pathologically. Tumors were found mainly in females (70%) without chronic liver diseases (87%). Association with tuberous sclerosis was found in only one case. Depending on the amount of tumor elements; blood vessels, so-called smooth muscle (SMC), and fat cells, the tumors were classified into 4 types : mixed (conventional), myomatous, angiomatous, and lipomatous type. Mixed type tumors represented mixed growth pattern, angiomatous type angiomatous pattern, and lipomatous type lipomatous pattern. In myomatous type tumor, a variety of cell types and growth patterns were found. Histologically, four types of SMC were found: spindle-shaped, epithelioid, interntediate, and pleomorphic cells. In epithelioid type SMC, clear cell and rhabdoid cells other than epithelioid cell, not otherwise specified, were occasionally seen. Also, a variety of growth patterns, including fascicular, nodular, solid, alveolar, trabecular, peliosis-like, and pleolnorphic patterns, were found. Atypical cell features were occasionally found in AML. Furthermore, invasive growth patterns into the surrounding hepatic parenchyma and/or into the portal triads were found in 60% of cases. However, distant metastasis was not found in all present cases so far, together with only one reported case of hepatic AML with distant metastases in the literature, indicating that invasive growth patterns found in AML do not simply indicate the sign of malignancy, and further study is needed to clarify them. Other histologic features that are frequently found in hepatic AML were extramedullary hematopoiesis, aggregates of foamy histiocytes, lymphocytic infiltration, hemorrhage and/or necrosis. I㎜unohistochemically, positive staining for HMB45 and melan A was found in all cases, and these reactions were considered to be specific for AML in the hepatic tunors. In conclusion, whenever pathologists encounter a strange hepatic tumor without chronic hepatic disease, they must try to stain immunohistochemically for HMB45 and melan A to establish a diagnosis of AML.