Abnormal growth of a pleomorphic leiomyosarcoma originating from the mesenteric vein associated with poor outcome after curative-intent resection: a case report

The abnormal growth of a PLMS prompted us to perform surgery with semi-urgent curative intent. Even after surgery, a large tumor recurrence in the retroperitoneum and lung metastasis were detected. Uncontrollable recurrent tumors can induce sepsis due to colorectal perforations. Notably, on pathological examination, the tumor was a well-differentiated LMS within the mesenteric vein, whereas the majority of tumors had a pleomorphic pattern, particularly in the extravascular region. Based on immunohistochemical analysis, the tumor was highly suspected to be derived from the mesenteric vein. Several studies have reported that the prognostic factors for an LMS are American Joint Committee on Cancer stage, tumor size, and tumor depth [4,5,6,7,8]. However, the rarity of a PLMS makes it difficult to identify prognostic variables after surgery with a curative intent. Considering the poor prognosis of a vessel-derived PLMS, an appropriate treatment strategy for achieving a long-term prognosis is unclear. Currently, curative-intent surgery is considered an essential treatment for a PLMS, regardless of its poor prognosis.

Vessel-derived LMSs account for < 2% of all the LMSs. In general, this type of tumor arises from large vessels such as the IVC, pulmonary vein, and femoral vein [9,10,11]. Owing to the nature of the vessel-derived LMS, it frequently metastasizes to distant sites, such as the lungs and liver via the vessel stream [10,11,12,13]. Previously, the rates of 5-year disease-free survival and overall survival (OS) were reported to be approximately 40% and 75%, respectively, in cases of an LMS derived from IVC [14]. Due to the scarcity of cases of LMSs derived from the mesenteric vein, prognosis is dependent on the tumor differentiation of an LMS. The pleomorphic type, tumor size (≥ 50 mm), and an advanced stage are regarded as risk factors for long-term prognosis. Considering that our patient had several risk factors for survival, rapid progression might have occurred even after resection with curative intent. To the best of our knowledge, this is the first case of a vessel-derived LMS arising from the mesenteric vein. It may delay diagnosis because of its deep and intravascular location [12, 15]. The tumor tends to grow and occlude vessels and collateral circulation even after complete occlusion. Most cases are diagnosed at advanced stages owing to a lack of surveillance and asymptomatic state [12, 16, 17]. In this case, the origin was suspected to be the mesenteric vein and the tumor size was already large when it was reported. Lung metastasis occurred 1 month after surgery, and a large intra-abdominal tumor appeared.

On pathological examination, the intravascular tumor was well differentiated, whereas most tumors had a pleomorphic pattern. According to the tumor growth pattern, it was presumed that the tumor infiltrated and proliferated outside the blood vessels as the tumor grew. The tumor originating from the intravascular LMS showed giant cells with strong nuclear atypia and spindle-shaped cells, consistent with the pleomorphic pattern. EVG and HE staining revealed that the intravessel tumor was well-differentiated.

The typical LMS component was positive for myogenic markers α-SMA, desmin, H-caldesmon, and calponin. The PLMS component was positive for myogenic markers. However, the positive ratio of myogenic markers for a PLMS was lower than that for an LMS. The MIB-1 labeling index in a PLMS was significantly higher than that in an ordinary LMS. In our case, α-SMA and desmin were positive, and pleomorphic spindled cells arranged in fascicles intersected at a right angle. The nucleus was centrally located and blunt-ended, and it appeared to be cigar shaped.

Neoadjuvant systemic chemotherapy, such as doxorubicin alone or in combination with ifosfamide or radiotherapy (RT), did not improve OS in patients with LMSs. To date, perioperative systemic chemotherapy and RT have not conquered the survival benefits of complete resection. Further studies are required to prolong the OS of patients with an LMS. Treatment methods for LMSs other than surgery have not yet shown any clear benefits; therefore, complete resection is the only established therapy. However, there are some trials for this [18, 19]. Determining the treatment for LMSs is complex and cases should be discussed among multidisciplinary team members.

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