Introduction: Mesenchymal tumors of the liver are rare, and in this group, myxoid leiomyomas are even rarer. So far, only 2 cases have been reported in the literature. Case Presentation: We aim to report the case of a 16-year-old female with a large lesion on the right hepatic lobe, grossly composed of gelatinous and heterogeneous tissue. Discussion: Histological evaluation revealed a benign mesenchymal neoplasm with expansive growth, paucicellular, with monotonous and dispersed spindle and ovoid cells, positive for α-smooth actin and h-caldesmon, without atypia or mitoses, consistent with the diagnosis of primary myxoid leiomyoma.

Introdução: Tumores mesenquimatosos do fígado são raros, e deste grupo os leiomiomas mixoides são ainda mais incomuns. Até ao momento foram apenas descritos dois casos na literatura. Caso clínico: Pretendemos efetuar a descrição de uma caso de uma menina de 16 anos com uma volumosa lesão no lobo hepático direito, que macroscopicamente era composta por um tecido gelatinoso e heterogéneo. Conclusão: Estudo histológico re-velou uma lesão mesenquimatosa benigna de crescimento expansive, pouco celular, com células fusiformes e ovaladas, monótonas, com expressão de actina do músculo liso e h-caldesmon, sem atipia nem mitoses, consistente com o diagnóstico de leiomioma mixoide.

Palavras-chave Leiomyoma mixoide, Fígado, Tumor mesenquimatoso

Primary liver cancer is the sixth most prevalent cancer worldwide, accounting for 5.7% of the overall incidence of cancer [1]. In 2018, the American Cancer Society estimated that liver and intrahepatic bile duct neoplasia corresponded to 4% of all new cases of cancer in men, with an estimated death rate of 6% among men and 3% among women [2, 3].

The most frequent types of neoplasia are epithelial, metastatic, or primary. Metastases to the liver are more common than primary tumors due to the dual blood supply of the liver from the portal and systemic circulation. Also, the hepatic sinusoidal epithelium has fenestrations which allow metastatic cells to penetrate more easily into the liver parenchyma.

Primary mesenchymal hepatic tumors vary from angiomyolipoma to synovial sarcoma. Primary leiomyoma of the liver is extremely rare; it is more commonly diagnosed in the uterus or gastrointestinal tract, but primary myxoid leiomyoma of the liver is an even rarer entity.

Clinical Summary

A 16-year-old female was referred to our hospital due to a large lesion which occupied the entire right hepatic lobe. This lesion was accidentally discovered during an abdominal ultrasound on routine examination. No relevant pathological background was identified.

Pathological Findings

Right hepatectomy was made, and the surgical specimen weighed 2,086 g and was 25 × 16 × 9 cm wide, encompassing a surgical margin with 19 × 6 cm; it had a pink and smooth Gleason capsule (Fig. 1a) with a fibrotic retraction of the posterior face. In cut section, there was a large, well-defined, expansive tumor formation occupying the majority of the right lobe of the liver with a width of 15 × 11 × 19 cm that was largely located on the margin of the surgical resection. The tumor consisted of a translucent, gelatinous tissue of heterogeneous texture and color that varied between yellowish and pinkish, sometimes with hemorrhagic and soft-consistency areas (Fig. 1b, c). The interface with the normal parenchyma was perceptible, without any capsule surrounding the tumor, with brownish, homogeneous and soft liver parenchyma.

Fig. 1.

Right hepatectomy, showing on cut section gelatinous tissue, with yellowish and red tissue.

Fig. 1.

Right hepatectomy, showing on cut section gelatinous tissue, with yellowish and red tissue.

Close modal

Histological evaluation revealed a benign mesenchymal neoplasm with expansive (Fig. 2a) and paucicellular growth (Fig. 2b), with monotonous and dispersed spindle and ovoid cells, with slightly eosinophilic cytoplasm and uniform nuclei, without atypia or mitoses (Fig. 2c). Stroma was markedly edematous and myxoid, well vascularized, with focal mononuclear inflammatory infiltrate. Bile ducts (CK7) or intratumoral hepatocytes (HepPar1) were not present. In the immunohistochemical study, spindle cells showed expression for α-smooth muscle actin and h-caldesmon (Fig. 2d), without staining for CD31, CD34, and desmin. Liver tissue adjacent to the neoplasia did not show any particular changes, nor did the margin of resection and the hilar structures.

Fig. 2.

Well-defined lesion, sometimes with fibrous tissue in the interface with nontumoral liver (a, HE, ×40), paucicellar (b, HE, ×100) and composed of monotonous spindle cells without mitoses (c, HE, ×200). Positive immunostaining for h-caldesmon (d, ×200).

Fig. 2.

Well-defined lesion, sometimes with fibrous tissue in the interface with nontumoral liver (a, HE, ×40), paucicellar (b, HE, ×100) and composed of monotonous spindle cells without mitoses (c, HE, ×200). Positive immunostaining for h-caldesmon (d, ×200).

Close modal

Primary mesenchymal tumors of the liver are very rare, accounting for less than 1% of all hepatic malignancies [1]. Hepatic angiosarcoma, leiomyosarcoma, and embryonal sarcoma are the most common mesenchymal tumors. The symptoms are unspecific with patients usually reporting abdominal pain, weight loss, weakness, loss of appetite, or vomiting. To these symptoms we may add enlargement of the liver, ascites, and jaundice, but these symptoms lack the specificity that would allow for a differential diagnosis between benign and malignant mesenchymal tumors. Therefore, it is difficult to make the diagnosis of malignant liver mesenchymal tumor because both its clinical presentation and imaging are nonspecific [4].

The main differential diagnoses encompass myxoma and mesenchymal hamartoma, the latter composed of loose connective tissue and epithelial bile duct or ductile-like in different proportions, with myxoid or collagenous stroma and arranged in a concentric way around the ducts [2]. Extensive tumor sampling is required in order to document the morphological spectra needed for the final diagnosis. In our case, the broad sampling provided the presence of spindle cells with smooth muscle differentiation required for the diagnosis and to rule out the presence of bile ducts and entrapped hepatocytes.

Primary myxoid leiomyosarcoma, rarely found in the liver, is also part of the differential diagnosis [5, 6]. However, there are no well-defined criteria for assessing the malignant potential of myxoid smooth muscle tumors outside the female genital tract [7]. Rubin and Fletcher [8] recommended this type of tumor to be considered as malignant when presenting any type of mitotic activity. Our tumor did not show necrosis nor mitosis.

Hawkins et al. [9] in 1980 established the criteria for the definition of hepatic leiomyomas, specifying that they should be composed of leiomyocytes and that there should be exclusion of leiomyoma in any other location, such as the uterus or gastrointestinal tract. The mean age of presentation was 43 years (range 5–87), with a mean size of 8.7 cm (range 2–30) and a female prevalence [10-12]. The review of 36 cases of hepatic leiomyomas done by Omiyale [13] in 2014 showed that 55.6% of the affected patients were women, with equal distribution between the right and left lobes. Imaging methods cannot differentiate between primary hepatic leiomyoma and other differential diagnoses. However, liver biopsy may be helpful [14].

The origin of the smooth muscle fibers from which these tumors are derived may be the walls of intravenous vessels, Ito cells (involved in myofibroblastic differentiation), or bile duct muscle cells or subcapsular mesenchymal cells [15-17], and the tumors may also be controversially associated with immunodeficiency states [10, 18]. The myxoid phenotype of these leiomyomas comes from the degeneration of muscle cells and increased interstitial matrix composed of mucopolysaccharide acid and glycoproteins [19]. Some cases are reported in association with Epstein-Barr virus infection in the context of immunosuppression, i.e., HIV infection or transplantation [20].

In short, we have described a very rare case of an extremely unusual mesenchymal neoplasia of the liver – myxoid leiomyoma – and the main differential diagnoses. As far as the authors are concerned, this is the third case reported in the literature [2, 15].

This case is important in order to increase awareness due to the rarity of the lesion. It may have a peculiar gross appearance, but clinical and radiological characteristics are unspecific, and larger tumors may give the impression of a malignant tumor. Histological study is fundamental and usually provides the right diagnosis.

The authors would like to acknowledge Alexandra Costa for performing English review. The current work was not subject to any type of funding.

This work was performed according to the Ethical Standards of Centro Hospitalar e Universitário de Coimbra.

The authors have no conflicts of interest to declare.

J.F. and R.C.O. developed the manuscript and collected clinical data. M.R.S. contributed to the diagnosis and figure drafts. L.T. and M.A.C. supervised the work and added critical content to the manuscript. All authors read and approved the final manuscript and agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

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