Leiomyosarcomas are tumors that originate in the smooth muscle cells of the muscularis propria. They account for less than 1% of all malignant tumors and close to 0.12% of tumors affecting the colon.1 Clinically, they can manifest with symptoms similar to those of other tumors of the colon (changes in bowel habit, anemia, and rectorrhagia), and from an endoscopic perspective, are typically observed as submucosal polyps. Leiomyosarcoma is an aggressive tumor, with an overall 5-year survival rate nearing 50%, whose main treatment is surgery, given the poor response to chemotherapy.2

A 75-year-old man had a past medical history of smoking, high blood pressure, and bronchial asthma. He sought medical attention for colicky abdominal pain, alleviated after bowel movements, and loss of weight and appetite of 3-month progression. In the laboratory work-up, only a positive fecal occult blood test stood out.

Colonoscopy was performed and detected an impassable stricture in the transverse colon, with adenomatous-appearing edges and ulceration, and was friable and bled spontaneously when touched by the endoscope (Fig. 1A). Multiple biopsies were taken and were negative for malignancy, given the subepithelial origin of the lesion. Likewise, an India ink tattoo was placed for later localization. A computed tomography (CT) scan (Fig. 1B) revealed a stricturing mass in the transverse colon, with no signs of metastatic lesions.

Figure 1.

(A) shows the endoscopic image of an impassable stricture with adenomatous edges and friable when touched by the endoscope. (B) CT image showing a mass in the transverse colon that narrows the intestinal lumen, without retrograde dilation. (C and D) Anatomopathologic study confirming the presence of a colonic leiomyosarcoma, positive for actin and desmin, and negative for GIST markers, such as CD117.

The patient was referred for surgery and operated on. The anatomopathologic study of the resected specimen reported tumor cells consistent with a mesenchymal tumor. The immunohistochemistry study was positive for actin and desmin, confirming the diagnosis of leiomyosarcoma (Fig. 1C and D).

Leiomyosarcoma is a rare stromal tumor that appears more frequently in patients in the sixth or seventh decade of life, predominantly in men. When it affects the gastrointestinal tract, more than 50% of tumors are located in the small bowel,3 and the second most frequent location is the colon. The tumor tends to have exophytic growth and may cause abdominal pain, rectorrhagia, or changes in bowel habit. Its presentation as a stricturing tumor or with intestinal obstruction is rare.

Diagnosis is made through colonoscopy, in which it is common to find a subepithelial polyp or nodule. Mucosal biopsies are not very useful, given that the tumors depend on the layer of the muscularis propria. Endoscopic ultrasound is very useful because it can distinguish the layer of tumor dependency and samples can be taken. However, in the case presented herein, it could not be performed due to the stricture caused by the tumor.

Leiomyosarcomas are aggressive tumors, frequently presenting with metastases at diagnosis, and their 5-year survival rate is low. The treatment of choice is surgical resection, given that the response to chemotherapy is very limited.4 Among the main prognostic factors are tumor size above 5 cm and the presence of metastasis.

The present case describes the diagnosis and treatment of this rare entity, highlighting its unusual presentation as a stricturing tumor of the colon.