Pleomorphous leiomyosarcoma of the mesocolon: a case report

Leiomyosarcoma is a rare tumor of the smooth muscle, but relatively frequent in the stomach and the small intestine. The mesocolic site is rare. Globally, leimyosarcoma represents less than 0, 1% of the malignant tumors found in the colon and the anus. Because of the similarities with other digestive tumors, namely mesenchymatous or benign tumors of the smooth muscle, the diagnosis of a pleomorphic sarcoma remains difficult even at the histological stage. Surgery is the mainstay of the therapy. We report a case of leiomyosarcoma of the mesocolon and discuss about its main characteristics in the view of the current literature about this pathological condition.


Introduction
Soft tissue sarcomas (STS) are an extremely diverse group of tumors occurring in every region of the human body and affecting all ages with significant morbidity and mortality. Soft tissue sarcomas include more than 35 different neoplasms derived from fat, muscle, nerve, fibrous, vascular, or deep skin tissue, and can be classified by their tissue of origin or their anatomical location [1].
The World Health Organization classifies liposarcomas into 5 histologic subtypes: welldifferentiated, dedifferentiated, myxoid, round cell, and pleomorphic sarcomas. Dedifferentiated histologic subtypes have a worse prognosis and an increased risk of local recurrence compared with well-differentiated liposarcomas [2]. Therefore, aggressive complete surgical resection of the tumor and adjacent organs is the mainstay of treatment for dedifferentiated liposarcomas [2]. We report here a case of pleomorphic leiomyosarcoma arising from the mesocolon and discuss its main characteristics and the management of this tumor along with a review of the literature.

Patient and observation
A -62-year-old female patient, who had past medical history of well treated pulmonary tuberculosis 6 years ago, that hospitalized because of a chronic abdominal pain for 10months.The patient reported weight loss about 6-kg during her illness .The physical examination found palpable per-umbilical mass (10 cm of diameter), hard and mobile relatively to the deeper and superficial neighboring structures. No lymph node or ascites was found. Laboratory exams: complete blood count was in normal range and tumor markers were negative.
Computer tomography scanning of the abdomen showed a round tissular mass with irregular edges, which makes 14 cm in its great axis, with central necrotic areas enhancement in the peripheral zones (Figure 1). A primitive pelvic tumor was suspected. At

Discussion
Pleomorphous sarcomas represent approximately 10 to 15% of the sarcoma of the smooth tissues of the adult [3]. The mean age at occurrence is about the 6 th decade of the life [4]. There is a slight male predominance, with a sex ratio of 1,6 [5,6].
The clinical symptomatology is not specific; can be abdominal pain or mass [7][8][9], alteration in the general condition [10,11], or signs related to a vascular or nervous compression [10]  Immunohistochemistry studies allow performing the diagnosis [3].
The benign or malignant nature of a pleomorphous sarcoma is not always easy to establish. Grading's system relying on histological parameters that have been described in order to better differentiate between the different tumoral grades and so the prognosis [12].
Like for the other sarcoma of the smooth tissues, prognostic factors on the histological type, the depth of the tumor, the high grade , the tumor size ( more than 5cm ) , tumoral necrosis great mitotic activity, infiltration in the neighboring structures, vascular invasion and the localization other than a limb, recurrence. Generally pleomorphous leiomorphous are considered as very aggressive and metastatic pleomorphous sarcomas.
Moreover, it has been shown that myogenic differentiation was a deleterious prognostic factors [13]. The treatment of pleomorphous sarcomas rely on surgery. The excision of the tumor in a monobloc fashion, with the viscera and without any tumoral effraction, is the standard of therapy [7]. Nodes excision is not systematic because involvement or recurrences at these sites are rare [8]. The high recurrence rate after surgery has led to investigations into the use of combined modality treatment for these tumours. As the most common form of relapse in retroperitoneal sarcoma is a local recurrence, adjuvant radiotherapy has been proposed to enhance the cure rates and improve the relapse free survival. Studies in extremity sarcomas have demonstrated improved local control rates when surgery was combined with radiotherapy. Globally, the sensitivity of sarcomas to irradiation is low [14].

Conclusion
Pleomorphous leiomysarcoma of the mesocolon is a rare tumor. The positive diagnosis of this condition can be made on pathological exam combined with immunohistochemistry studies after surgery.
The association of an adjuvant therapy remains controversial; however, adjuvant chemotherapy can be suggested in the case of a bad prognosis, a short time after the surgical procedure.