Leiomyosarcoma arising from gastrointestinal mesentery is a rare but aggressive pathology. A first case report on mesenteric leiomyosarcoma was published by Derechin et al. in 1956 . Common presenting complains in patients with leiomyosarcoma includes palpable mass, abdominal pain, and abdominal fullness, and middle age females are mostly affected. The proliferation of smooth muscle cell secondary to estrogen is a likely explanation for this increase incidence [4, 5]. Our patient was presented with complain of abdominal distension for 4 months associated with nausea and vomiting.
In 1963, Yannopoulos et al. in their case series reported five cases of leiomyosarcoma, while three out of these five tumors were reported to be originated from mesentery . Most of the primary mesenteric lesions are benign, and differential diagnosis of the malignant disease includes GIST, leiomyosarcoma, malignant myofibroblastic tumor, solitary fibrous tumor, liposarcoma, and lymphoma [3, 6, 7].
Imaging plays a crucial role in the pre-operative workup of mesenteric leiomyosarcoma. Ultrasound and CT scan both help in diagnosis, localization, identification of metastatic involvement, and characterization of disease nature. The solid lesion most likely to be malignant while cystic tends to be benign on CT scan imaging . In our case, a solid area of the cyst was around 80 to 90%.
Per cutaneous biopsy is usually contraindicated as it can result in tumor seeding, thus the only means of definitive diagnosis is a histopathological examination of the specimen with immunohistochemical staining and genetic analysis . CD 117 helps to differentiate GIST from leiomyosarcoma, as the former are CD 117 positive. Leiomyosarcoma universally expresses SMA (smooth muscle actin) while desmin expression is variable . In our case on histopathology, SMA and desmin were diffusely positive while CD 34 and CD 117 were negative. Pathologically, Ranchod M. et al. reported in their study that high mitotic activity strongly indicates the malignant potential of leiomyosarcoma . In terms of mitotic activity, in our case, up to 18 to 20 mitoses per 10 HPF including atypical mitotic figure were reported.
Surgical excision of mesenteric leiomyosarcoma with clear margins is a treatment of choice . Surgeons should try to completely excise the smooth muscle cells tumor with at least 4 in. of healthy tissue and corresponding mesentery in order to improve the survival rate. The good chemotherapeutic response is reported for this condition unlike GIST . Long-term follow-up is recommended as it helps in early recognition of the recurrent or metastatic disease and facilitating curative resection [5, 11]. Neoadjuvant high-dose long-infusion Ifosfamide (HLI) and external beam radiotherapy (EBRT) reduce the mass for performing a full resection. Some authors suggest a combination of preoperative EBRT and chemotherapy with surgery and intraoperative radiotherapy (IORT) seems to improve the overall survival rate .
Agarwal K et al. reported that the site of tumor contributes to the grave prognosis of this disease as it prevents the detection of tumor at an earlier stage . Most of the tumors are already metastatic at the time of diagnosis to lung or liver. Hashimoto et al.  demonstrated only 21% 5-year survival rate of 44 leiomyosarcomas arising from the retroperitoneum and mesentery. Hence, these patients need careful long-term follow-up.