Malignant melanoma of small intestine.

The purpose of this article is to present a challenging case of recurrent gastrointestinal bleeding caused by malignant melanoma of the small intestine and to discuss the diagnostic approach, highlighting the role of advanced endoscopic techniques. The patient underwent extensive diagnostic evaluation, including repeated gastroscopies, colonoscopies, two double-balloon enteroscopies, scintigraphy with labeled erythrocytes, and capsule endoscopy. Capsule endoscopy provided a decisive contribution to the diagnostic process, guiding further clinical management including segmental small intestine resection with regional lymphadenectomy. Histopathological examination of the resected tissue revealed malignant melanoma of the spindle cell type, infiltrating the mucosa, submucosa, and part of the muscular layer. No primary cutaneous lesion or distant metastases were detected following comprehensive diagnostic evaluation. In patients with suspected lower gastrointestinal bleeding, when standard endoscopic procedures do not allow to identify the source, location in the small intestine should be considered. In such cases, early implementation of advanced diagnostic techniques, such as capsule endoscopy and double-balloon enteroscopy, is recommended. These methods allow identification of lesions in small intestine segments with limited accessibility. A crucial step in the diagnostic process was capsule endoscopy, which enabled identification of an actively bleeding lesion in the distal segment of the small intestine.