Giant accessory hepatic lobe accompanied by inflammatory pseudotumor

A 25-year-old female was admitted to the hospital 6 months after the discovery of a liver mass during a physical examination. She has no abdominal pain or abdominal wall masses. Liver function and alpha-fetoprotein (AFP) levels are normal. Computed tomography (CT) scan (Figure 1A-1C) shows a large, well-defined, approximately 9.9 cm × 9.3 cm × 8.5 cm, low-density lesion in the splenic gastric space, closely related to the left lobe of the liver. Enhancement suggests that the lesion is connected to the upper edge of hepatic segment 2; it is supplied by branches of the left hepatic artery, portal vein left branch, and drains into the left hepatic vein. The patient underwent resection of the left lobe liver mass, and the postoperative pathology revealed an accessory hepatic lobe (AHL) with fatty liver and associated inflammatory pseudotumor (Figure 1D). AHL is a rare congenital liver tissue anomaly, including Riedel’s lobe and ectopic liver tissue, occurring in less than 1% of the population. It is still uncertain what causes AHL, but one hypothesis suggests that it may be linked to a deformity in the caudal foregut of the endoderm and an irregular splitting of the tissue buds that occurs in the third week of pregnancy.

Figure 1 CT imagings of giant accessory hepatic lobe (arrows). CT scan (A-C) shows a large, well-defined mass in the splenic gastric space, closely related to the left lobe of the liver. Under the microscope (D), a large number of inflammatory cells infiltrate, predominantly composed of plasma cells. Lymphocytes, histiocytes, neutrophils, and a few eosinophils are also observed. There is interstitial fibrovascular proliferation, and the cells show no atypia. HE ×400. CT, computed tomography; HE, hematoxylin-eosin.

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