Extremely Rare CT and MRI Findings of Peritoneal Leiomyoma Mimicking Hepatic Mass: A Case Report

Abstract

Leiomyoma is a common benign tumor from smooth muscle cells, mostly in the uterus. Peritoneal leiomyomas (PLs) are extremely rare and mostly reported as disseminated peritoneal leiomyomatosis. However, to the best of out knowledge, radiologic findings of isolated PL are not reported in English literature. Herein, we introduce the radiologic findings of PL mimicking hepatic mass in a 34-year-old female. CT showed a mass with curvilinear heterogeneous enhancement at the liver's peripheral area. On MRI, the mass showed gradual and heterogeneous enhancement on gadoxetic acid-enhanced MRI and diffusion restriction. The radiologic diagnosis was a benign hepatic tumor, such as degenerated hemangioma, adenoma, and inflammatory myofibroblastic tumor; however, the mass was diagnosed as PL pathologically.

Keywords: Leiomyoma; Liver; Magnetic Resonance Imaging; Peritoneum; Tomography, X-Ray Computed.

Fig. 1. A 34-year-old female with a peritoneal leiomyoma mimicked hepatic mass.

A. Precontrast axial CT image shows a low attenuated mass in the extrahepatic area of liver segment six. On contrast-enhanced axial and coronal images in the portal phase, the mass shows rim and irregular enhancement and a suspicious gap (arrows) between it and the liver parenchyma. B. Axial non-enhanced T2-weighted MRI reveals a mass abutting liver segment six with signal intensity higher than that of the liver. Coronal T2-weighted MRI shows a suspicious gap (arrows) between the mass and hepatic parenchyma. In precontrast T1-weighted MRI, the mass shows lower signal intensity relative to that of the liver. Contrast-enhanced arterial, portal, and transitional phases show gradual incomplete mass rim enhancement. The mass shows homogeneous low signal intensity at the hepatobiliary phase and high signal intensity on DWI (b = 800 s/mm²) and low ADC value on the ADC map. C. An ovoid solid mass is present in the peritoneum near the liver, measuring 5.8 cm × 4.7 cm × 3.7 cm (left) and its histology showed intersecting fascicles of slender-tapered spindle cells (middle, hematoxyling & eosin stain, × 100). Immunohistochemical stain for desmin revealed positivity in the tumor cells, consistent with leiomyoma (right, × 200). ADC = apparent diffusion coefficient, DWI = diffusion-weighted imaging, WI = weighted image