Teaching Case

A 73-year-old man was studied because nausea, vomit, abdominal distension and anorexia.

A 73-year-old man was admitted to our hospital complaining about nausea, vomit, anorexia and abdominal distension since few months. He had a melanoma diagnosis eleven years ago .

Melanoma is a malignant tumor of melanocytes, which are the cells that make the pigment melanin and are derived from the neural crest (neuroectodermal origin). Although most melanomas arise in the skin, they may also arise from mucosal surfaces or at others sites to which neural crest cells migrate. The annual age-adjusted incident of melanoma is 20 per 100,000 persons among whites. Risk factors for melanoma include white race, sun sensitivity, family history of melanoma, and melanocytic nevi. We recognize clinicopathologic cellular subtypes of malignant melanoma: superficial spreading, nodular, lentigo maligne, acral lentiginous, miscellaneous unusual type. When melanoma cells spread from primary tumor, they can be concentrated in: lymph nodes and subcutaneous (50-70%), lung (70-80%),spleen (54-77%),brain (36-54%),bone (20-40%), gastrointestinal tract (26-58%), heart (40-45%) and adrenal glands. Gastrointestinal metastases from malignant melanoma may manifest as mucosal or submucosal masses, serosal implants, or carcinomatosis. They arise more commonly in the mesentery or distal small bowel than the proximal gastrointestinal tract or colon. In small bowel, haematogeneuos metastases arise in submucosal layer, as small intramural nodes then they become polipoids with intraluminal extension. Central ulceration is frequent. Ultrasonography may show ileoileal intussusception seen as “ring in ring sign” where outer hypoechoic ring is formed by intussuscipiens(invaginating ileum) and inner hypoechoic round area is formed by intussusceptum( entering limb of invaginated ileum) with mucosal melanoma metastases in center. Hyperechoic crescent between two rings is formed by invaginated mesenteric fat. Besides Doppler sonogram of intraluminal mucosal metastases reveals strong capillary blood flow (hypervascular mass). On small bowel follow through examination, metastases from malignant melanoma tend to be longer lesions with extensive ulceration, wider channels, and little or no evidence of obstruction. . In smaller lesions there is a “target lesion” or an ox’s eye where ulcer lesion is very wide if it is compared with metastatic mass. Linear fissurations appear as a wheel’s spoke because they go to the center of the niche. In bigger lesions, necrosis is formed with an ulcer lesion as an anaerismatic dilatation. Dissemination can be single but it often is multiple. Characteristics locations from melanoma are along anti-mesenteric border because intraparietal ramifications of vassels are placed there. Spiral CT well shows four distinct patterns of disease( intraluminal masses, ulcerating lesions, diffuse infiltration, implants) and it also demonstrates mesenteric nodal involvement and intussusception . Intussusception, on CT, is characterized by thickening of the affected bowel segment and by the presence of intraluminal fat density material , a concentric ring or “target” lesion and an intra-luminal soft-tissue mass. Metastasis in distal ileum shows a moderate signal intensity on True Fisp images as opposed to the high signal intensity of the distended lumen and the mesenteric fat. Tumor local extent is best shown on pre-contrast-spoiled gradient-echo images and post gadolinium T1 weighted fat suppression images. Post-gadolinium 3D Flash fat sat can identify and characterize tumor. The degree of prestenotic dilatation , the peritoneal extension of neoplasm and associated lymphadenopathy is well visualized with all MRE sequences(True-Fisp, HASTE,FLASH) The only treatment is surgical resection.