Primary leiomyosarcoma of the liver is an exceptionally rare and aggressive mesenchymal malignancy. Because of its rarity, little is known about its radiologic findings, especially in gadoxetic acid-enhanced MRI. Herein, we report a case of primary leiomyosarcoma of the liver with emphasis on CT and MRI findings.

A 70-year-old man was referred to our hospital for evaluation of a liver mass discovered during the evaluation of anorexia, weight loss, and general weakness. The patient had no history of liver disease or alcohol abuse, and his medical history was unremarkable. Physical examination revealed a palpable upper abdominal mass, ascites, and lower extremity edema. Laboratory tests revealed elevated aspartate aminotransferase of 68 U/L (reference range, 0-40), alkaline phosphatase of 384 U/L (40-129), total bilirubin of 4.89 mg/dL (0-1.2), direct bilirubin of 3.52 mg/dL (0.13-0.47), and gamma-glutamyltransferase of 840 U/L (10-71). The levels of carbohydrate antigen 19-9 and protein induced by vitamin K absence-II were elevated to 146 U/mL (<34) and 51 mAU/mL, respectively. Alpha-fetoprotein and carcinoembryonic antigen levels were within the normal range.

Abdominopelvic CT showed multiple masses up to 17 cm in size. The dominant mass was nearly replaced the right liver, and multiple smaller nodules scattered in both hemilivers (Fig. 1). On non-contrast CT (Fig. 1A), the masses showed heterogeneous attenuation. On arterial phase (Fig. 1B), the masses generally showed hyperenhancement with a nonenhancing area in the center of larger masses. On portal phase (Fig. 1C and 1D), the mass still showed heterogeneous attenuation and a capsule-like area of low density at the periphery, but no clear washout. In addition, an 11.5 cm left adrenal metastasis was found (arrow on Fig. 1D). Metastasis to the T10 vertebra, left iliac bone, and multiple metastatic lung nodules were also found (not shown). No abnormality was observed in other solid organs, suggesting that the primary tumor originated in the liver.

Liver MRI with gadoxetic acid was performed for further evaluation (Fig. 2). T2-weighted images (Fig. 2A and 2B) (echo time = 83-98 ms) showed multiple well-defined masses with moderately hyperintense signal. Note the whirled or bundle-like structures. Bright T2 hyperintense area in the center may represent necrosis. On diffusion-weighted image and ADC map (Fig. 2C and 2D) (b = 1000 s/mm2), the masses showed relatively severe diffusion restriction. On non-contrast T1-weighted image (Fig. 2E), multifocal T1 hyperintense areas were noted within the mass, reflecting hemorrhage. On arterial phase (Fig. 2F), the masses show varying degrees of enhancement with equivocal washout on portal phase (Fig. 2G). Hepatobiliary phase image (Fig. 2H) showed hypointensity of the masses. There was no significant signal drop on in-phase and opposed-phase images.

Percutaneous liver biopsy was performed for confirmatory diagnosis. Hematoxylin and eosin staining (Fig. 3A) revealed intersecting bundles of spindle cells. Immunohistochemical staining was positive for smooth muscle actin (Fig. 3B) and desmin (Fig. 3C) and negative for DOG-1 (Fig. 3D) and S-100 protein. The Ki-67 index was 20%. Based on these findings, a diagnosis of leiomyosarcoma was made.

Primary liver sarcomas are rare, accounting for only 1-2% of all primary liver malignancies [1]. Among patients who underwent surgical resection of primary liver sarcomas, leiomyosarcoma was responsible for 13.9% of liver sarcomas, with other types of sarcomas including epithelioid hemangioendothelioma, angiosarcoma, embryonal rhabdomyosarcoma, carcinosarcoma, giant cell sarcoma, spindle cell sarcoma, and undifferentiated pleomorphic sarcoma accounting for another 70-80% of liver sarcomas [2].

Leiomyosarcoma of the liver is thought to arise from smooth muscle cells in the liver parenchyma or surrounding structures such as the round ligament, hepatic veins, inferior vena cava, bile ducts, or gallbladder [3, 4]. Symptoms, when present, are often vague and may include abdominal discomfort, weight loss, and nonspecific gastrointestinal complaints, leading to delays in diagnosis [5]. Because of its nonspecific clinical presentation, aggressive behavior, and limited treatment options, diagnosis and management of liver leiomyosarcoma is challenging.

Radiologically, liver leiomyosarcoma lacks distinctive features, and its appearance can vary widely on ultrasound, CT, and MRI scans, further complicating radiologic diagnosis. On CT and MRI, leiomyosarcoma typically presents as a large, heterogeneous, and ill-defined mass with irregular margins, necrotic areas, and variable enhancement patterns [5-8]. In particular, contrast enhancement of internal and peripheral areas can be observed [5-7]. Other reports have shown a large hypervascular mass with hemorrhage or liquefied necrosis. Intratumoral hemorrhage, as seen in the current case, can be detected by the presence of high signal intensity on T1-weighted images. Occasional encapsulation on MRI has also been reported [7, 8]. Diffusion restriction in viable tumor has also been observed, reflecting the high cellularity of the tumor [9]. Whirling or bundle-like intratumoral appearance as demonstrated in the present case has not been reported previously. We speculate that these imaging findings may correspond to spindle cells, as observed on histopathologic analysis. Given that this appearance is rarely seen in more common primary liver cancers such as hepatocellular carcinoma or cholangiocarcinoma, it may be of diagnostic significance.

Several primary or secondary liver tumors may present with similar radiologic findings [10, 11]. For heterogeneously enhancing liver malignancies with hemorrhage, the differential diagnosis should include hepatocellular carcinoma, angiosarcoma, neuroendocrine carcinoma, epithelioid hemangioendothelioma, and other sarcomas. In fact, the initial radiologic diagnosis of the current case included hepatocellular carcinoma, neuroendocrine carcinoma, and angiosarcoma. In retrospective review, the absence of a history of chronic liver disease and equivocal portal washout may lead to a lower prioritization of hepatocellular carcinoma in the differential diagnosis. In neuroendocrine carcinoma, the whirling appearance of the tumor seems unusual. In angiosarcoma, bizarre and prominent intratumoral vessels may be an important clue [12]. For secondary liver tumors, hemorrhagic liver metastasis such as metastatic melanoma or choriocarcinoma could be considered. For benign lesions, hemorrhagic hemangioma, peliosis, adenoma, hemorrhagic liver cyst, or traumatic lesions may be included in the differential diagnosis [11].

Due to its rarity and aggressive nature, there are no standardized treatment guidelines for liver leiomyosarcoma. However, surgical resection with curative intent remains the mainstay of treatment whenever feasible, followed by adjuvant chemotherapy to provide the best chance for long-term survival [9, 13, 14]. Adjuvant chemotherapy or radiotherapy may be considered in selected cases, although their efficacy is remains to be established [13]. Unfortunately, the overall prognosis for leiomyosarcoma remains poor.

In conclusion, primary leiomyosarcoma of the liver is a rare and challenging disease with a variable clinical course. Its diagnosis relies on a combination of histopathologic examination and immunohistochemical staining, while its management is primarily surgical. Of the reported variable radiologic findings, leiomyosarcoma could be considered as a differential diagnosis in a large heterogeneous hepatic mass with hemorrhage among other more common hemorrhagic liver masses.