Renal oncocytoma is a non–malignant neoplasm of the renal parenchyma formed from epithelial cells (oncocytes) of the distal collecting tubules. It often proceeds asymptomatically, sometimes causes macrohematuria, aching lower back pain, increased blood pressure, secondary varicocele on the affected side. Ultrasound of the kidneys, radiation methods (MRI, CT, PET-CT), biopsy are used for diagnosis and differential diagnosis. Surgical treatment: minimally invasive radiofrequency destruction, partial or total nephrectomy.
ICD 10
D30.0 Benign neoplasms of the urinary organs (kidneys)
Meaning
Oncocytoma is the second most common benign kidney tumor after adenoma. It accounts for 3-7% of all solid formations of the body. In most cases, oncocytomas are single, unilateral tumors, however, in 5-13% of cases, multiple formations are diagnosed, in 3-6% – with multifocal growth. Oncocytoma of the kidney affects men 2 times more often, mainly people over 60 years old are ill. Oncocytic tumors can also develop in other glandular organs: salivary, thyroid and parathyroid glands, pituitary gland, adrenal glands, pancreas, prostate gland.
Causes
The etiological factors causing the growth of renal neoplasms have not been clarified. It is known that some tumors (cysts, oncocytomas, renal cell carcinoma) are often found in genetic pathologies: Burt-Hogg-Dube syndrome, Hippel-Lindau disease, tuberous sclerosis. There is also a higher risk of kidney oncocytoma in patients with lung cancer, carcinoid tumors, and myeloma.
Other risk factors for the appearance of renal oncocytoma include:
- smoking: increases the likelihood of developing kidney tumors by 2 times;
- taking nephrotoxic medications: diuretics, NSAIDs, hormones, cytostatics;
- harmful production factors: contact with asbestos, cadmium, chemicals, radiation exposure;
- chronic renal failure requiring hemodialysis.
Pathomorphology
Oncocytoma grows from the epithelium of the collecting tubules of the kidney. Oncocytes are large eosinophilic cells containing a large number of mitochondria. Currently, they are commonly referred to as a type of endocrine cells – apudocytes. These cells have high metabolic activity: they participate in the metabolism and production of enzymes, amino acids, synthesize biogenic amines (serotonin). Oncocytes are widely represented in various organs: in the salivary glands, thyroid, larynx, esophagus, trachea and lungs, pancreas, pituitary gland, kidneys, adrenal glands.
The mechanisms of occurrence of oncocytoma are unknown, but its pathomorphological characteristics have been well studied. Kidney oncocytoma usually has the shape of a node with clear boundaries, the average size is 5-8 cm (can grow up to 26 cm). The color of the tumor on the incision varies from light yellow to red-brown. In the center of the nodular formation, a star-shaped scar may be detected, hemorrhages, cystic changes in tumor tissues are characteristic. In some cases, oncocytomas invade blood vessels and paranephral tissue.
Microscopically, oncocytoma cells – oncocytes – are large, predominantly mononuclear (there are also binucleated cells), have a rounded or polygonal shape, fine-grained eosinophilic cytoplasm, surrounded by hyalinized stroma. Tumor cells are nested, alternate with solid fields and trabeculae.
Classification
There is no generally accepted classification of renal oncocytoma. The most practical importance in oncourology is the division of the tumor by size, influence on the surrounding structures of the urinary system, malignant potential.
Depending on the diameter, oncocytomas of small sizes (up to 4 cm), medium sizes (from 4 to 8 cm) and large sizes (more than 8 cm) are distinguished. Taking into account the state of excretory function, there is a clinical variant of pathology that proceeds without compression of the urinary tract and with compression of the urinary tract.
Based on the histological picture , 3 variants of renal oncocytoma are distinguished:
- benign;
- with undetermined malignant potential;
- malignant (oncocytic carcinoma).
Symptoms
In more than 80% of cases, the tumor behaves asymptomatically and does not violate the patient’s condition even when reaching large sizes. The remaining patients develop a symptom complex, including pulling pains in the lower back, visible traces of blood in the urine (macrohematuria), arterial hypertension.
When an oncocytoma reaches gigantic dimensions, a tumor formation in the abdominal cavity is palpated, an asymmetry in the lumbar region becomes noticeable. Compression of the neoplasm of nearby vessels with impaired blood flow through the inferior vena cava causes men to develop varicocele on the side of the affected kidney. In the presence of multiple bilateral formations infiltrating the entire renal parenchyma, they talk about oncocytomatosis.
Complications
Macrohematuria is dangerous by the formation of blood clots, which cause obstruction of the ureter and an attack of renal colic. An infectious inflammation, pyelonephritis, may begin in the affected kidney. In clinical nephrology, cases of oncocytoma development in a kidney transplant have been described.
The symptoms of oncocytoma are non-specific and should always cause cancer alertness. Despite the fact that kidney oncocytoma belongs to benign tumors, cases of its malignant degeneration and aggressive course with infiltration of paranephral tissue, vascular invasion, metastasis have been noted. In addition, approximately 10% of patients are diagnosed with both oncocytoma and renal cell carcinoma at the same time.
Diagnostics
Asymptomatic renal oncocytoma is detected when a patient is examined for another disease of the urinary system. If there are complaints of pain in the kidney area, an admixture of blood in the urine, it is necessary to consult a nephrologist. To detect micro- or macrohematuria, a general urine test is prescribed. In order to confirm the diagnosis, determine the morphological type of the tumor is carried out:
- Ultrasound of the kidneys. With renal echography, an oncocytoma is visualized as a hypoechoic formation that causes deformation of the organ. The size of the node often does not exceed 10 cm. Ultrasound in Doppler mode detects hypervascularization of oncocytoma, which can lead to an erroneous diagnosis of kidney cancer.
- CT of the kidneys. On native tomographic images, a rounded tumor with clear contours is determined. After contrasting, an avascular stellate scar in the center, a tumor capsule on the periphery, a vascular pattern in the form of a wheel with spokes becomes noticeable. On MRI, the invasion of blood vessels, parotid tissue and the cup-pelvic system is clearly visible.
- PET-CT. Radionuclide diagnostics with 18F-fluorodeoxyglucose demonstrates the presence of an iso- or hypointensive signal in relation to the renal parenchyma, as well as a lower accumulation of a radioactive isotope than in renal parenchyma cancer.
- Kidney biopsy. The histological diagnosis is confirmed after a fine needle biopsy followed by microscopic examination of the tissue sample. The immunohistochemical analysis of the biopsy allows for an accurate differential diagnosis.
Differential diagnosis
If a kidney neoplasm is suspected, pathomorphological exclusion of other solid neoplasms of a benign and malignant nature is necessary. Among them:
- papillary adenoma;
- angiolipoma;
- hemangioma;
- leiomyoma;
- reninoma (juxtaglomerular cell tumor);
- chromophobic kidney carcinoma;
- lymphoma;
- metastatic tumors of the kidney.
Treatment
Surgical intervention is a first-line treatment, since in most cases it is possible to make a diagnosis only during an intraoperative biopsy. In solitary oncocytomas with a diameter of less than 4 cm, nephron‒sparing surgery is recommended – open or laparoscopic resection of the kidney, enucleation of nodular formation with preservation of parenchyma is possible.
With small neoplasms in patients with severe concomitant pathology or a tumor of a single kidney, a minimally invasive technology can also be used ‒ radiofrequency thermal destruction of oncocytoma by percutaneous, laparotomic or laparoscopic access.
In case of multifocal organ damage, as well as if it is impossible to exclude a high malignant potential of oncocytoma, radical nephrectomy is performed. With any volume of resection, oncological principles must be observed, but there is no consensus among clinicians about the need for lymphadenectomy.
Prognosis and prevention
The long-term prognosis after surgical removal of a solid benign renal oncocytoma is favorable. Relapses occur rarely, but annual ultrasound monitoring is required to exclude them in the future. More uncertain prognosis in patients with oncocytomatosis, oncocytic carcinoma, oncocytoma of a single kidney.
Given the ambiguity of the etiology of oncocytoma, possible risk factors should be excluded: smoking, uncontrolled use of drugs, industrial hazards. Renal pathology leading to the formation of CRF should be treated in a timely manner.