Adenomatoid tumour of the liver

Abstract

An unusual primary adenomatoid tumour arising in the normal liver is described. Hepatectomy was performed, and the patient is alive and free of disease 1 year postsurgery. Grossly, the tumour showed a haemorrhagic cut surface with numerous microcystic structures. Histological examination revealed cystic or angiomatoid spaces of various sizes lined by cuboidal, low-columnar, or flattened epithelioid cells with vacuolated cytoplasm and round to oval nuclei. The epithelioid cells were entirely supported by proliferated capillaries and arteries together with collagenous stroma. Immunohistochemical studies showed that the epithelioid cells were strongly positive for a broad spectrum of cytokeratins (AE1/AE3, CAM5.2, epithelial membrane antigen and cytokeratin 7) and mesothelial markers (calretinin, Wilms' tumour 1 and D2-40). These cells were negative for Hep par-1, carcinoembryonic antigen, neural cell adhesion molecule, CD34, CD31 and HMB45. Atypically, abundant capillaries were observed; however, the cystic proliferation of epithelioid cells with vacuoles and immunohistochemical profile of the epithelioid element were consistent with hepatic adenomatoid tumour.

Figure 1. (A) CT revealed that the tumour was hypointense pre-enhancement and highly enhanced in the arterial phase with early washout (arrows). (B) Enhanced MRI after gadolinium injection. The tumour was hyperintense on T1-weighted images in the arterial phase but demonstrated prolonged enhancement in the portal venous and delayed phases (arrows). (C) Angiography showed a definite tumour with an arterioportal shunt (the artery (A5, filled arrow) and the portal vein (P5, open arrow)). (D) Grossly, the 1.5 cm soft mass in the subcapsular region showed a haemorrhagic cut surface with numerous microcystic spongiotic structures but was non-encapsulated.

Figure 2. Histological findings by H&E staining. (A) The well-circumscribed nodular tumour comprising cystic spaces. (B) Cystic spaces of various sizes supported by collagenous stroma. (C) The cystic or angiomatoid spaces are lined with cuboidal, low-columnar or flattened epithelioid cells, and contain abundant red blood cells and colloid-like materials (D). (E) The epithelioid cells show small- to large-sized vacuoles or eosinophilic cytoplasm with round to oval nuclei. (F) The border of the tumour is surrounded by fine collagenous bands, and neither epithelioid cells nor stromal cells infiltrated the liver parenchyma.

Figure 3. Histological findings by immunohistochemical staining. (A) Non-epithelioid cells are diffusely positive for α-smooth muscle actin and show the arterial wall (arrow). (B) CD31-positive capillaries surround the epithelioid cells. The epithelioid cells are diffusely positive for AE1/AE3 (C), and calretinin (D).