Inflammatory pseudotumor of the liver. Report of the fine needle aspiration cytologic findings in a case initially misdiagnosed as malignant

The fine needle aspiration (FNA) cytologic features are described in a case of inflammatory pseudotumor of the liver (xanthogranuloma), a disease generally regarded as of unknown etiology. The initial FNA findings were those of an acute exudative process, with atypical biliary duct epithelium and hepatocytes. These were interpreted as verifying the radiologic impression of a malignancy. Histologic study of subsequently resected nodules revealed the true nature of the case. As the lesion evolved, granulomatous inflammation supervened, characterized by numerous foamy histiocytes and lesser populations of plasma cells and lymphocytes. Numerous gram-positive cocci were readily demonstrated, suggesting that the lesion was an unusual tissue response to an intrahepatic bacterial infection. The lesion eventually resolved with prolonged antibiotic therapy.