Background

Primary hepatic leiomyoma (PHL), a rare manifestation of tumors in the liver [1, 2]; is mainly characterized by its mesenchymal tissue origin in the liver, and no cases of leiomyoma are identified in the gastrointestinal and urinary tracts or elsewhere in the body [3].

To date, the pathogenic mechanisms underlying this disease remain unclear. While it has been postulated that the neoplasia may arise from atypical growth of hepatic vessels and abnormal proliferation of bile ducts [1, 4, 5] this has not been well validated by scientific research.

Since 1926, when the first case of PHL was described, most PHL cases have been reported among patients suffering from acquired immunity deficiency syndrome (AIDS) or AIDS in combination with Epstein-Barr virus (EBV) infection, or taking immunosuppressive medications after organ transplantation [2, 6]. To our knowledge, PHL in immunocompetent patients is extremely rare.

In this case report, we describe an unusual case of PHL in a middle-aged Chinese woman who was asymptomatic with no immunosuppressive disorders, no history of hepatitis or other liver disease, and no history of immunosuppressive medication use. After a successful laparoscopic partial hepatectomy, the patient has an excellent prognosis.

Case presentation

Patient description

A 46-year-old Chinese woman consulted a physician in our department for an intrahepatic mass incidentally detected by an abdominal ultrasound (US) during her annual physical examination. After a 7-cm hypoechoic mass in the right lobe of the liver was identified and confirmed, the patient was admitted to our hospital for further investigation and treatment of the hepatic lesion. She reported no immunosuppressive medication use and no history of liver disease or surgery.

Clinical examination

No mass and discomfort and no signs of other clinical symptoms were detected during the abdominal examination. Hematological and serum biochemical profiles were within normal ranges. Tumor markers including alpha-fetoprotein (AFP), carcinoembryonic (CEA), carbohydrate antigens 199 (CA199), and carbohydrate antigens 125 (CA125) were also normal.

Further investigation of the hepatic lesion with computed tomography (CT) revealed a slightly hypodense 6.5 × 7.2 cm mass in the right lobe of the liver with heterogenous enhancement of arterial phase, and prolonged enhancement through portal venous phase and the lesion (Fig. 1a, b, c). No other abnormalities were identified in the remaining liver tissue and elsewhere the abdomen.

Fig. 1
figure 1

Abdominal CT scan images of the patients. CT images demonstrate (a) heterogenous enhancement in the artery phases; b progressive enhancement in the portal venous phases; and c prolonged enhancement in the balanced phases. d An image during the laparoscopic partial hepatectomy. e Tumor tissue samples

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As the CT imaging was inconclusive, further evaluation with magnetic resonance imaging (MRI) as well as US-guided fine needle aspiration (FNA) biopsy of the tumor for pathological examination was recommended. However, the patient preferred an operation without additional preoperative assessment of the lesion.

Treatment and outcome

In view of the benign features of the hepatic lesion and in accordance with our patient’s choice of treatment, we carried out laparoscopy (Olympus, Tokyo, Japan). A 12-mm optical trocar at the umbilicus as well as three other trocars was used. Two 12-mm trocars were used through the epigastrium and right upper abdomen. A 5-mm trocar was used through the right abdomen near the anterior axillary line. After a laparoscopic exploration and US, a solid 6.5 cm × 7.0 cm × 7.5 cm mass was clearly located in the segment 6 of the liver and outwardly protruding from the liver surface (Fig. 1d). We decided to perform laparoscopic partial hepatectomy. Hepatic parenchyma was performed using an UltraCision Harmonic Scalpel (Ethicon Endo-Surgery, Cincinnati, OH, USA). The branches of the Glissonian pedicles and hepatic vein within the liver were clipped using a Hem-o-lok® (Teleflex Medical, Morrisville, NC, USA) and a titanium clip (TSCS, Hangzhou, China), and then transected. We put the surgical specimen into a laparoscopic disposable specimen bag (Xueli, Nanchang, China) through the epigastrium incision, and to avoid expanding the incision we cut the specimen into small pieces in the bag before taking them out (Fig. 1e). Finally, the surgical area was carefully examined and a drainage tube was not placed. Seven days after surgery, the patient was discharged from hospital. After a 2-year follow-up, no recurrence or metastasis occurred.

Final diagnosis

Postoperative pathological examination revealed a benign smooth muscle tumor derived from the mesenchymal tissue of the liver with clearly visible margins and with no evidence of necrosis or tumor invasion (Fig. 2a, b). Immunohistochemistry (IH) showed strong reactivity for smooth muscle actin (SMA) (+), desmin (+), and H-caldesmon (+) (Fig. 2c, d, e), but not for Dog-1 (−), CD117 (−), S-100 (−), and CD34 (−) (Fig. 2f, g, h, i). According to the diagnostic criteria for PHL, the patient was finally diagnosed with PHL.

Fig. 2
figure 2

Characterization of primary hepatic leiomyoma staining. a Tissue sample staining × 4; b tissue sample staining × 40; c desmin (+); d H-caldesmon (+); e SMA (+); f Dog-1 (−); g CD117 (−); h; S-100 (−); i CD34 (−)

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Discussion and conclusions

Since 1926 when the first case of PHL was described, just 22 immunocompetent cases have been reported in the medical literature (Table 1). Here we reported the 23rd case. The average age was 48.17 years and the male to female ratio was 6:17. The mass size ranged from 3 cm to 30 cm. Thirteen cases were found in the right lobe of liver, eight cases in the left lobe, and two cases in the caudate lobe.

Table 1 PHL without immune-compromised cases in medical literature
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A PHL diagnosis needs to satisfy the following criteria: (1) the tumor originates from the hepatic mesenchymal tissue; and (2) there are no primary tumors elsewhere in the body. However, despite this clear criteria for identifying this rare type of intrahepatic tumor, a successful preoperative diagnosis of PHL is challenging, mainly due to imaging features being similar with other benign hepatic tumors as well as a lack of specific characteristics to guide physical and laboratory examinations [5, 8, 23].

Several common imaging patterns have been identified in PHL patients. On US scans, PHL appears as heterogenous hypoechoic nodules [16, 18, 20]; a finding also seen in our case. In CT imaging, hypodense lesions are widely reported with marked enhancement in the arterial and portal venous phases, occasionally in the peripheral phase, and with prolonged enhancement in the equilibrium phase [5, 16, 20]. On MRI, the PHL usually presents a lower signal in T1-weighted images and a higher signal in the T2-weighted images [2, 18, 23]. In addition, lesion characteristics (irregular margins) on hepatic angiography have been reported in a few PHL cases [15, 18]. Non-invasive, preoperative imaging patterns on US, CT, MRI, and angiography can not define PHL.

Of the reported PHL cases in the literature, Sousa and colleagues achieved an accurate diagnosis of PHL in a healthy middle-aged woman by undertaking an imaging-guided fine needle aspiration (FNA) and a 18G tru-cut liver biopsy of the tumor tissue [20]. Sadler and colleagues reported two cases with preoperative diagnosis on liver biopsy: one case with mesenchymal mixed tumor of the liver but an accurate diagnosis could be not reached in the other case [26]. In our patient, like most reported cases, a non-invasive, preoperative diagnosis with imaging features was inconclusive.

After a postoperative pathological examination was carried out on the biopsy specimen, the pathological features were noteworthy. A benign smooth muscle tumor containing the mesenchymal tissue with clear margins was visualized. Positive staining for SMA, which is observed in most reported PHL cases and is a hallmark of PHL, was confirmed in this case. Moreover, positive staining for desmin and H-caldesmon, as observed in some reported PHL cases [14], was also noticed in our patient, whereas vimentin was negatively expressed in the tumor tissue (also reported in some PHL cases). In addition, negative staining for Dog-1 and CD117 distinguished PHL from the gastrointestinal stromal tumors (GIST), while negative reactivity for S-100 ruled out leiomyoma of the central nervous system and CD34 excluded vascular leiomyoma. The patient thus fulfilled the two criteria and was eventually diagnosed with PHL.

In this case, given the benign features of the hepatic lesion, which usually signifies treatment with surgery [27] as well as our respect for the patient’s preferred choice of treatment, we performed a laparoscopic partial hepatectomy of the right lower liver [24]. The procedure appeared to be highly effective in this case, and our patient has a good prognosis and is expected to have no recurrence in the long term.

In conclusion, the imaging and pathological features of the patient should be added to previously reported aspects of this disease. Moreover, although PHL is extremely rare, it should still be considered a possibility. Surgical intervention is effective in treating PHL.