Benign and Malignant Renal Tumors

Benign Renal Tumors

Angiomyolipoma is the most common benign renal tumor, consisting of blood vessels, smooth muscle cells, and fat.
Angiomyolipoma occurs in 25-50% of patients with tuberous sclerosis.
Tuberous sclerosis is a genetic disease caused by mutations in the TS1 and TS2 genes, leading to brain tumors and skin lesions (Ash-Leaf Patches).
Oncocytoma accounts for 10% of renal tumors and is encapsulated with a tan or brown color.
Oncocytoma is composed of eosinophilic cells packed with mitochondria and is associated with genetic changes, including loss of chromosomes 1 and Y.

Renal Cell Carcinoma (RCC)

RCC is the most common type of kidney cancer, accounting for 85% of all renal malignancies.
RCC occurs most commonly in elderly individuals (60-70 years old) and affects males twice as often as females.
Known risk factors include smoking, obesity, hypertension, unopposed estrogen therapy (Tamoxifen), exposure to asbestos, petroleum products and heavy metals, chronic renal failure and acquired cystic disease.
Familial forms of RCC account for 4% of cases.
Von Hippel-Lindau (VHL) syndrome is a familial form of RCC caused by mutations in the VHL gene on chromosome 3.
Hereditary clear cell carcinoma and hereditary papillary carcinoma are other familial forms of RCC.
RCC typically presents as a spherical, yellow, variegated tumor with necrotic, cystic, and hemorrhagic areas.
The tumor may extend into the renal vein, leading to metastasis.
Clear cell carcinoma is the most common type of RCC, characterized by clear or granular cytoplasm.
Papillary RCC is characterized by a papillary growth pattern, is frequently multifocal and bilateral, and often presents at an early stage.
Sporadic papillary RCC is associated with trisomy 7, 16, 17 and loss of the Y chromosome.
Familial papillary RCC is associated with mutations in the MET proto-oncogene on chromosome 7 and trisomy 7.
Chromophobe RCC is a less common type of RCC that originates from the cortical collecting ducts or their intercalated cells.
Chromophobe RCC is generally associated with a good prognosis and low risk of metastasis due to multiple deletions of entire chromosomes (1, 2, 6, 10, 13, 17, 21).
Sarcomatoid carcinoma is a dedifferentiated form of RCC with sarcoma-like features.
RCC is often asymptomatic and discovered incidentally.
Symptomatic cases may present with hematuria, costovertebral pain, a mass, and constitutional symptoms such as fever, malaise, and weight loss.
Advanced stage RCC can metastasize to the lungs and bones.
Paraneoplastic syndromes associated with RCC include polycythemia (due to erythropoietin production), hypercalcemia (due to parathyroid hormone-related protein production), Cushing's syndrome (due to ACTH production), and hypertension (due to renin production).
The five-year survival rate for RCC is approximately 70%.
Stage is a crucial prognostic factor and is based on tumor size, renal vein involvement, and extension beyond the kidney capsule.
Small tumors (2-3 cm) may be treated with partial nephrectomy.

Nephroblastoma (Wilms' Tumor)

Nephroblastoma is a rare but common childhood tumor, affecting children up to 5 years old.
Genetic abnormalities in chromosome 11, specifically mutations in the WT-1 and WT-2 genes (Wilms' tumor suppressor genes), are associated with an increased risk.
Patients with nephroblastoma may also have Denys-Drash syndrome or Beckwith-Wiedemann syndrome.
Nephroblastoma typically appears as a large, well-circumscribed, soft, tan-gray homogeneous tumor.
Microscopically, it consists of blastemal, stromal, and epithelial elements.
Nephroblastoma commonly presents with an abdominal mass, hematuria, pain, or hypertension.
The long-term survival rate for nephroblastoma has reached 90%.

Renal Pelvis Carcinoma

The renal pelvis is lined by transitional epithelium (urothelium).
Renal pelvis carcinoma may be classified as transitional cell carcinoma or squamous cell carcinoma, the latter associated with long-standing irritation.
Renal pelvis carcinoma accounts for 5-10% of renal neoplasms and often presents at an early stage with painless hematuria.
Pain or a mass may develop due to hydronephrosis (obstruction).
Multifocal tumors are possible.
Prognosis varies based on stage and grade.
Despite removal by nephrectomy, the five-year survival rate is 50%.

Ureteral Carcinoma

The ureters are lined by transitional epithelium (urothelium).
Similar to the renal pelvis, ureteral carcinoma can be classified as transitional cell carcinoma or squamous cell carcinoma.
Narrowing or strictures in the ureter can occur at the ureteropelvic junction, ureterovesical junction, and the crossing of the iliac vessels.
In females, ureters are located close to the uterine arteries and cervix.