The paper reports the case of a patient with leiomyosarcoma of the duodenum who underwent radical duodenocephalopancreatectomy and survived for 22 months after the operation. Following a review of the international literature on the topic, the diagnostic procedures and prognostic criteria of this uncommon tumour are discussed. In conclusion, leiomyosarcoma always presents considerable problems of diagnosis even with the aid of biopsy and only surgery can lead to recovery in a limited number of cases.