Hepatic Angiomyolipoma: Mutation Analysis and Immunohistochemical Pitfalls in Diagnosis

Abstract

Aims

Hepatic angiomyolipoma (AML) often shows epithelioid morphology with inconspicuous fat. Epithelioid component can mimic hepatocellular adenoma (HCA) or carcinoma (HCC). The aims were to examine the expression of commonly used markers for HCA or HCC in hepatic AML, and highlight pitfalls in diagnosis.

Methods and results

Resected hepatic AML (n=16) were reviewed; reticulin stain, immunohistochemistry for GS, β-catenin, LFABP were performed along with Sanger sequencing of exon 3 of CTNNB1 and next generation sequencing (NGS). Predominant epithelioid component (≥ 50%) was seen in 80% of cases. Foamy macrophage was present in 33% of cases. High risk histologic features were often present in tumors with benign outcome: marked atypia (19%), mitoses (20%) and necrosis (33%). GS staining (>10% of tumor) was seen in epithelioid component in 13 (87%) cases, and was diffuse (>50% of tumor) in 6 (40%) cases. LFABP staining or nuclear β-catenin staining was not seen in any case. Sanger sequencing and NGS did not reveal CTNNB1 mutation in any tested case. NGS demonstrated TSC2 mutations in all 5 tested cases.

Conclusions

Predominance of epithelioid component resembling HCA or HCC is common in hepatic AML. Absence of LFABP and presence of fat can be mistaken for HNF1α- inactivated HCA. Diffuse GS staining can be mistaken for β-catenin activated HCA or HCC. Diffuse GS expression is not related to CTNNB1 mutation. All tested cases showed TSC2 mutation, supporting this as the driving genetic event for hepatic AML.

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from #ORL-AlexandrosSfakianakis via ola Kala on Inoreader http://ift.tt/2G1M43b