Hepatic angiomyolipoma: report of two cases with emphasis on smear cytomorphology and the use of cell block with immunohistochemical stains

Angiomyolipoma is a benign mesenchymal lesion that occurs most commonly in the kidney. Its occurrence in the liver is relatively rare. We report two cases of hepatic angiomyolipoma diagnosed by ultrasound-guided, needle aspiration biopsy. One of the patients was a previously healthy 62-yr-old woman who presented with a hepatic mass incidentally during a healthy examination. The other patient was a 67-yr-old man, a victim of chronic hepatitis C, who was found to have a hepatic tumor in the right lobe during regular follow-up. Cytologic preparations of the two hepatic masses showed some mature adipocytes admixed with clusters of variable-sized mesenchyme-like cells with fibrillar cytoplasm and indistinct cytoplasmic borders. Some of the cells were round to oval and others were spindle shaped with oval, cigar-shaped or elongated nuclei. The nuclear chromatin was fine and some cells showed round nucleoli. No thick-walled blood vessels were noted in the cytological smears. In the cell block preparations, a mixture of thick-walled blood vessels, mature adipose tissue, and bundles of variable-sized smooth muscle cells were noted. The spindle or epithelioid smooth muscle cells were positive for vimentin, alpha-smooth muscle actin, and human melanoma black (HMB)-45 but negative for desmin and S100 protein in immunohistochemical stains. The purpose of the current study is to describe cytological features of this lesion with differential diagnosis because pathologists may be called on to render a diagnosis on needle aspiration. HMB-45 has been proved to be a sensitive marker for the smooth muscle component of angiomyolipoma. Cell block preparations assisted with immunohistochemical staining should be emphasized for definite diagnosis. Although a surgical procedure may still be necessary once a diagnosis of angiomyolipoma is made, treatment may be tailored for a less aggressive procedure than for malignant hepatic nodules.