Congenital Mesoblastic Nephroma
Mesoblastic nephroma (MN) comprises about 5% of childhood kidney tumors. The median age of diagnosis is 2 months and more than 90% of cases appear within the first year of life. Twice as many males are diagnosed as females. The diagnosis should be questioned when applied to individuals older than 2 years. When diagnosed in the first 7 months of life, the 5-year event-free survival (EFS) rate is 94% and the overall survival (OS) rate is 96%.
Grossly, MNs appear as solitary, unilateral masses indistinguishable from nephroblastoma. Microscopically, they consist of spindled mesenchymal cells. They can be divided into two major types: classic and cellular. Classic MN is often diagnosed by prenatal ultrasound or within 3 months after birth and closely resembles infantile fibromatosis. Infantile fibrosarcoma and cellular MN contain the same t(12;15)(p13;q25) chromosomal translocation suggestive of a potential linkage. The risk for recurrence within MN is closely associated with the presence of a cellular component and with stage.
Renal Cell Carcinoma
Malignant epithelial tumors arising in the kidneys of children account for more than 5% of new pediatric renal tumors; therefore, they are more common than CCSK or RTK. Renal cell carcinoma (RCC), the most common primary malignancy of the kidney in adults, occurs rarely in children younger than 15 years. In the older age group of adolescents (aged 15-19 years), approximately two-thirds of renal malignancies are RCC. The annual incidence rate is approximately 4 per 1 million children compared with an incidence of Wilms tumor of the kidney that is at least 29-fold higher. RCC in young patients has a different genetic and morphologic spectrum than that seen in older adults.[30,31,32,33]
RCC may be associated with other conditions, including the following:
- von Hippel-Lindau (VHL) disease: VHL disease is an autosomal dominant condition in which blood vessels within the retina and cerebellum grow excessively. The gene for VHL disease is located on chromosome 3p25.3 and is a tumor-suppressor gene, which is either mutated or deleted in patients with the syndrome.
Screening for the VHL gene is available. To detect clear cell renal carcinoma in these individuals when the lesions are less than 3 cm and nephron-sparing surgery can be performed, annual screening with abdominal ultrasound or magnetic resonance imaging (MRI) is recommended beginning at age 8 to 11 years.
- Tuberous sclerosis: In tuberous sclerosis, the renal lesions may actually be epithelioid angiomyolipoma (also called perivascular epithelioid cell tumor or PEComa), which is associated with aggressive or malignant behavior and expresses melanocyte and smooth muscle markers.[36,37]
- Familial RCC: Familial RCC has been associated with an inherited chromosome translocation involving chromosome 3. A high incidence of chromosome 3 abnormalities has also been demonstrated in nonfamilial renal tumors.
Succinate dehydrogenase (SDHB, SDHC, and SDHD) is a Krebs cycle enzyme gene that has been associated with the development of familial renal cell carcinoma occurring with pheochromocytoma/paraganglioma. Germline mutations in a subunit of the gene have been reported in individuals with renal cancer with no history of pheochromocytoma.[39,40]
- Renal medullary carcinoma: A rare subtype of RCC, renal medullary carcinoma, may be associated with sickle cell hemoglobinopathy. Renal medullary carcinomas are highly aggressive malignancies characterized clinically by a high stage at the time of detection, with widespread metastases and lack of response to chemotherapy and radiation therapy.[ Level of evidence: 3iiA] Survival is poor and ranges from 2 weeks to 15 months, with a mean survival of 4 months.[41,42,43,44]
- Hereditary leiomyomatosis: Hereditary leiomyomatosis (of skin and uterus) and RCC is a distinct phenotype caused by dominant inheritance of a mutation in the fumarate hydratase gene. Screening for RCC starting as early as age 5 years has been recommended.[45,46]
- Second malignant neoplasm: RCCs have been described in patients several years after diagnosis and therapy for neuroblastoma.