Angiomyolipoma: A benign tumor containing vascular, adipose, and muscle elements. It occurs most often in the kidney with smooth muscle elements (angiolipoleiomyoma) in association with tuberous sclerosis. (Dorland, 27th ed)Tuberous Sclerosis: Autosomal dominant neurocutaneous syndrome classically characterized by MENTAL RETARDATION; EPILEPSY; and skin lesions (e.g., adenoma sebaceum and hypomelanotic macules). There is, however, considerable heterogeneity in the neurologic manifestations. It is also associated with cortical tuber and HAMARTOMAS formation throughout the body, especially the heart, kidneys, and eyes. Mutations in two loci TSC1 and TSC2 that encode hamartin and tuberin, respectively, are associated with the disease.Lymphangioleiomyomatosis: A disease characterized by the progressive invasion of SMOOTH MUSCLE CELLS into the LYMPHATIC VESSELS, and the BLOOD VESSELS. The majority of the cases occur in the LUNGS of women of child-bearing age, eventually blocking the flow of air, blood, and lymph. The common symptom is shortness of breath (DYSPNEA).Kidney Neoplasms: Tumors or cancers of the KIDNEY.Epithelioid Cells: Characteristic cells of granulomatous hypersensitivity. They appear as large, flattened cells with increased endoplasmic reticulum. They are believed to be activated macrophages that have differentiated as a result of prolonged antigenic stimulation. Further differentiation or fusion of epithelioid cells is thought to produce multinucleated giant cells (GIANT CELLS).Angiolipoma: A benign neoplasm composed of a mixture of adipose tissue and blood vessels. (Dorland, 27th ed)Melanoma-Specific Antigens: Cellular antigens that are specific for MELANOMA cells.Lipoma: A benign tumor composed of fat cells (ADIPOCYTES). It can be surrounded by a thin layer of connective tissue (encapsulated), or diffuse without the capsule.Neoplasms, Adipose Tissue: Neoplasms composed of fatty tissue or connective tissue made up of fat cells in a meshwork of areolar tissue. The concept does not refer to neoplasms located in adipose tissue.Adenoma, Oxyphilic: A usually benign glandular tumor composed of oxyphil cells, large cells with small irregular nuclei and dense acidophilic granules due to the presence of abundant MITOCHONDRIA. Oxyphil cells, also known as oncocytes, are found in oncocytomas of the kidney, salivary glands, and endocrine glands. In the thyroid gland, oxyphil cells are known as Hurthle cells and Askanazy cells.Flank Pain: Pain emanating from below the RIBS and above the ILIUM.Hemangioma: A vascular anomaly due to proliferation of BLOOD VESSELS that forms a tumor-like mass. The common types involve CAPILLARIES and VEINS. It can occur anywhere in the body but is most frequently noticed in the SKIN and SUBCUTANEOUS TISSUE. (from Stedman, 27th ed, 2000)Nephrectomy: Excision of kidney.Liver Neoplasms: Tumors or cancer of the LIVER.Myelolipoma: A rare benign tumor of the adrenal gland, several centimeters in diameter, composed in varying proportions of adipose tissue, lymphocytes, and primitive myeloid cells, probably a developmental abnormality. (Dorland, 27th ed)Tomography, X-Ray Computed: Tomography using x-ray transmission and a computer algorithm to reconstruct the image.Neoplasms, Multiple Primary: Two or more abnormal growths of tissue occurring simultaneously and presumed to be of separate origin. The neoplasms may be histologically the same or different, and may be found in the same or different sites.Retroperitoneal Space: An area occupying the most posterior aspect of the ABDOMINAL CAVITY. It is bounded laterally by the borders of the quadratus lumborum muscles and extends from the DIAPHRAGM to the brim of the true PELVIS, where it continues as the pelvic extraperitoneal space.Renal Veins: Short thick veins which return blood from the kidneys to the vena cava.Radiography, Abdominal: Radiographic visualization of the body between the thorax and the pelvis, i.e., within the peritoneal cavity.Pelvic Neoplasms: Tumors or cancer of the pelvic region.