We present a case of leiomyosarcoma of the colon whose first manifestation was a pulmonary metastasis. The patient was a 74-year-old woman with a history of chronic obstructive pulmonary disease and hysterectomy with double adnexectomy and subsequent brachytherapy for endometrial adenocarcinoma 5 years ago. She consulted for dyspnoea of 2 months' evolution, without associated cough, haemoptysis or general syndrome.

Blood tests were normal. Chest X-ray and chest CT scan revealed a right parahilar mass measuring 5 x 3 cm. A biopsy of the mass was taken by bronchoscopy showing a mesenchymal tumour with positive imnunohistochemistry for vimentin and negative for c-KIT compatible with leiomyosarcoma.

An extension study was performed with gastroscopy, colonoscopy and abdominopelvic CT scan, which was negative. With a diagnosis of primary leiomyosarcoma of the right lung, a right pneumonectomy was performed, confirming the histology of leiomyosarcoma in the surgical specimen.

One month after the right pneumonectomy, the patient presented with abdominal pain with nausea, vomiting and episodes of rectorrhagia. Colonoscopy showed a polylobulated mass with a neoplastic appearance in the ascending-blind colon and abdominal CT scan with dilatation of the small bowel loops showing a doughnut-shaped image at the level of the terminal ileum-blind ileum compatible with intestinal invagination with a probable underlying tumour lesion.

Emergency surgery was performed, revealing small bowel obstruction due to invagination of the terminal ileum at the level of the tumour in the cecum. A right hemicolectomy was performed.

Histopathological study of the surgical specimen showed that it was a leiomyosarcoma measuring 6 x 4 x 2.8 cm, affecting the mucosa, submucosa, muscle and serosa with a high number of mitoses (more than 10 mitoses per 10 high magnification fields) and immunohistochemistry positive for actin and vimentin and negative for c-KIT. This finding demonstrates that the LMS had its origin in the colon and the lung tumour was metastatic.

During this second postoperative period, the patient again presented respiratory complications and died one month after abdominal surgery.