Invasive growth of hepatic angiomyolipoma; a hitherto unreported ominous histological feature

• Published in: Histopathology Vol. 48; no. 7; pp. 831 - 835
• Main Authors: Nonomura, A, Enomoto, Y, Takeda, M, Tamura, T, Kasai, T, Yosikawa, T, Nakamime, H
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01.06.2006; Blackwell
• Subjects: Adult; Aged; Aged, 80 and over; Angiomyolipoma - metabolism; Angiomyolipoma - pathology; Antigens, Neoplasm; Biological and medical sciences; Female; hepatic angiomyolipoma; HMB-45; Humans; Immunohistochemistry; invasive growth; Investigative techniques, diagnostic techniques (general aspects); Liver Neoplasms - metabolism; Liver Neoplasms - pathology; Male; Medical sciences; Melanoma-Specific Antigens; Middle Aged; Neoplasm Invasiveness; Neoplasm Proteins - analysis; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; perivascular epithelioid cells; uncertain malignant potential; invasive growth; Anatomic pathology; hepatic angiomyolipoma; Digestive system; Growth; Liver; Tumor; HMB-45; Histology; Angiomyolipoma; uncertain malignant potential; perivascular epithelioid cells
• ISSN: 0309-0167; 1365-2559
• DOI: 10.1111/j.1365-2559.2006.02427.x

Aims : Although histological features of hepatic angiomyolipoma (AML) are highly variable, true malignant change is extremely rare. The aim was to review the histological features of invasive growth and clinical outcomes in 39 cases of hepatic AML. Methods and results : An invasive growth pattern into surrounding hepatic parenchyma, portal triads and/or around hepatic veins was found in 24 of 39 tumours (62%). One variant showed tumour cells replacing hepatocytes within the liver cell cords. The other consisted of portal or perivascular invasive growth along blood vessels. In the former pattern, small isolated tumour cell clusters were occasionally found in the vicinity of the main mass, showing a sprouting pattern. Although these histological features suggest malignancy, distant metastases were not found in any of the cases within a mean follow‐up period of 6.8 years. Conclusions : A previously unrecognized histological feature of an invasive growth pattern, which suggests malignancy and might promote an erroneous diagnosis, was frequently found in hepatic AMLs. However, among about 180 reported hepatic AMLs, including the present cases, only one hepatic AML with distant metastasis has been reported to date and nearly all hepatic AMLs behave in a benign fashion. Therefore, pathologists should not overdiagnose malignancy based solely on the histological invasive growth patterns described in this paper.