Ileal intussusception due to intestinal metastases from primary malignant melanoma of the lung.

Primary malignant melanoma of the lung (PMML) is an uncommon tumor with very few cases reported in the literature that satisfy the required criteria to establish a primary bronchial origin. We report a case of a 44-year-old man with acute abdominal distress and a right pulmonary roentgenographic opacity. A cranial-thoracic-abdominal CT scan confirmed the presence of a pulmonary nodule with bilateral cerebral metastases and marked dilatation of intestinal loops. At laparotomy an ileal intussusception was noted and an ileal resection was done. The resected intestinal segment contained three endoluminal polypoidal formations. Histological and immunohistochemical analyses showed the presence of multiple sites of melanoma. These lesions as well as the brain lesions clearly appeared metastatic. The patient underwent further evaluation to identify a primary site of melanoma; bronchoscopy was performed with biopsy of the pulmonary nodule. Pathology revealed a neoplastic process of fusiform cells, with focal presence of melanic inter- and extracellular pigment. The immunohistochemical analysis confirmed the diagnosis of PMML. We discuss the criteria for diagnosis and histogenesis of PMML along with this unusual presentation.