RESUMO
This is a case report of an extremely rare primary malignant melanoma presenting in the retroperitoneum of a 30 years old female. She was operated in a District General Hospital with a presumptive diagnosis of hydatid cyst of right lobe of liver. The patient bled profusely on exploration and the surgeon packed the abdomen and referred her to our emergency, where she was received in shock. After resuscitation she was operated on the next available list and was found to have a very vascular, pigmented, retroperitoneal mass measuring 10-x 12-cm lying in front of the infrarenal IVC pushing the duodenum towards the midline. It was completely excised. Histopathology showed it to be a malignant melanoma. Upon subsequent examination and extensive workup, no evidence of a primary malignant melanoma was found. There was no past history of a melanoma which may have regressed spontaneously or excised. After extensive search of literature we could not find another report of a primary retroperitoneal melanoma