What are the other Names for this Condition? (Also known as/Synonyms)

• Renal Oncocytoma

What is Oncocytoma of Kidney? (Definition/Background Information)

• Oncocytoma of Kidney is a benign solid tumor of the kidney that is generally diagnosed in middle-age and older adults. In many cases, the tumors are found incidentally while examining the individual for other medical conditions
• The tumor is known to be occasionally associated with certain genetic disorders, such as Birt-Hogg-Dubé syndrome and tuberous sclerosis. In such cases, oncocytomas may involve both the kidneys (bilateral presentation)
• The cause of formation of Oncocytoma of Kidney is typically unknown. However, studies indicate certain abnormalities involving mitochondrial DNA may be responsible for tumor formation
• The signs and symptoms of Oncocytoma of Kidney depend upon the size of the tumors and may include abdominal pain and blood in urine. Some tumors can grow to large sizes leading to symptoms due to mass effect of the tumor. Large tumors may also adversely affect kidney function
• Typically, a surgical excision of Oncocytoma of Kidney with its entire removal is the treatment of choice. The prognosis is excellent with its complete removal, since it is usually a benign tumor. However, the prognosis may be influenced by the presence of genetic syndromes (if any)

Who gets Oncocytoma of Kidney? (Age and Sex Distribution)

• Oncocytoma of Kidney constitutes approximately 5% of all adult renal epithelial tumors
• It is usually observed in adults over the age of 50 years (peak age 55 years), although a wider age group may be involved
• More males are affected than females (male-female ratio 2:1)
• No specific ethnic or racial preference has been recorded

What are the Risk Factors for Oncocytoma of Kidney? (Predisposing Factors)

Currently, the following risk factors have been identified for Oncocytoma of Kidney:

• Oncocytosis of kidney, which is the presence of numerous oncocytic lesions without necrosis in the kidney
• Tuberous sclerosis: It is an inherited genetic disorder that can cause the formation of other tumor types, such as astrocytomas, rhabdomyomas, phakomas, oncocytomas, and angiofibromas, at various body locations
• Birt-Hogg-Dubé syndrome: It is a hereditary disorder that is characterized by numerous tiny follicles on the skin. This rare condition also affects the kidneys and lungs
• Renal Oncocytoma can also be associated with renal cell carcinoma

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one's chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Oncocytoma of Kidney? (Etiology)

The cause of Oncocytoma of Kidney formation is mostly unknown. The tumor is sometimes seen against a background of certain genetic syndromes.

• Study research indicates certain mitochondrial DNA mutations as being probably responsible for tumor development
• Also, according to studies, abnormalities have been observed in chromosome 1 (in nearly 90% of the tumors, when both kidneys are involved; and, in nearly 30% of the solitary kidney tumors)

What are the Signs and Symptoms of Oncocytoma of Kidney?

The signs and symptoms of Oncocytoma of Kidney depend on the size and location of the tumor. It can also vary from one individual to another. In general, small tumors are asymptomatic and large tumors can cause signs and symptoms. The kidney symptoms may be caused due to mass effect (presence of bulky tumors).

The signs and symptoms of Renal Oncocytoma may include the following:

• The size of the tumor may vary from a few centimeters to 12 cm
• It may be present as an abdominal mass
• Tumors associated with genetic disorders may affect both kidneys (and are multiple in numbers), while solitary tumors are seen in sporadic cases
• The tumor is solid, well-defined and demarcated
• It may be associated with urinary tract infections, blood in urine, increased blood pressure, and flank pain
• In general, large tumors can severely affect the functioning of the kidney that is involved. Tumors growing to larger sizes can cause compression of adjoining organs and structures, which can result in abdominal pain

Additionally, the signs and symptoms of any associated genetic disorder may be observed.

How is Oncocytoma of Kidney Diagnosed?

The diagnosis of Oncocytoma of Kidney may involve the following tests and procedures:

• Complete physical exam with evaluation of medical history
• Plain X-ray of the abdomen
• Ultrasound scan of the abdomen
• CT or CAT scan with contrast of the abdomen may show a well-defined mass. This radiological procedure creates detailed 3-dimensional images of structures inside the body
• MRI scans of the abdomen: Magnetic resonance imaging (MRI) uses a magnetic field to create high-quality pictures of certain parts of the body, such as tissues, muscles, nerves, and bones. These high-quality pictures may reveal the presence of the tumor
• Urine analysis to check for the presence of blood cells
• Kidney function test
• Intravenous pyelogram (IVP): A dye is injected into the blood vessels and the image of kidney structure is obtained
• Vascular angiographic studies of the tumor may be performed

Invasive diagnostic procedures such as:

• Laparoscopy: A special device is inserted through a small hole into the abdomen, to visually examine it. If necessary, a tissue sample is obtained for further analysis. Exploration of the abdomen using a laparoscope is called ‘exploratory laparoscopy’
• Laparotomy: The abdomen is opened through an incision for examination, and if required, a biopsy sample obtained. Exploration of the abdomen using laparotomy procedure is called ‘exploratory laparotomy’

Although the above modalities can be used to make an initial diagnosis, a tissue biopsy of the tumor is necessary to make a definitive diagnosis to begin treatment. The tissue for diagnosis can be procured in multiple different ways which include:

• Fine needle aspiration (FNA) biopsy of the kidney tumor: A FNA biopsy may not be helpful, because one may not be able to visualize the different morphological areas of the tumor. Hence, a FNA biopsy as a diagnostic tool has certain limitations, and an open surgical biopsy is preferred
• Core biopsy of the kidney tumor
• Open biopsy of the kidney tumor

Tissue biopsy:

• A tissue biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
• Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
• Sometimes, the pathologist may perform special studies, which may include immunohistochemical stains, molecular testing, and very rarely, electron microscopic studies to assist in the diagnosis

A differential diagnosis, to eliminate the following tumor types is considered, before arriving at a definitive diagnosis:

• Eosinophilic variant of chromophobe renal cell carcinoma (RCC)
• Clear cell RCC with granular cytoplasm
• Metanephric adenoma/adenofibroma

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Oncocytoma of Kidney?

The complications of Oncocytoma of Kidney may include:

• Stress and anxiety due to a concern of kidney cancer
• Chronic renal failure affecting kidney function, if tumors are large; especially, when the condition is bilateral (affecting both kidneys). In majority of cases, the tumor affects one kidney
• Damage to the muscles, vital nerves, and blood vessels, during surgery
• Post-surgical infection at the wound site is a potential complication
• Complications from an underlying genetic disorder (if any)

How is Oncocytoma of Kidney Treated?

The treatment options vary from one individual to another. The treatment measures for Oncocytoma of Kidney may include the following:

• Small and asymptomatic tumors: The healthcare provider may recommend a ‘wait and watch’ approach for small-sized tumors presenting mild signs and symptoms, after a diagnosis is made
• Surgical intervention with complete excision can result in a cure. It can also help reduce the chances of tumor recurrence

The surgical treatment methods may include:

• Endoscopic surgery
• Nephron-sparing surgery
• Partial or complete nephrectomy

A partial or complete nephrectomy may be considered, when large-sized tumors are noted in the kidneys.

• A kidney dialysis may be required, if the kidney function is severely compromised due to renal failure
• Postoperative care is important: A minimum activity level is ensured, until the surgical wound heals
• Follow-up care with regular screening may be recommended by the healthcare provider

How can Oncocytoma of Kidney be Prevented?

• Current medical research has not established a method of preventing Oncocytoma of Kidney
• Regular medical screening at periodic intervals with tests and physical examinations are recommended

What is the Prognosis for Oncocytoma of Kidney? (Outcomes/Resolutions)

• The prognosis of Oncocytoma of Kidney depends upon the severity of the signs and symptoms. It also depends upon the overall health of the individual. However, since these tumors are benign, the prognosis is generally excellent
• If the tumor is associated with a genetic disorder, such as tuberous sclerosis complex or Birt-Hogg-Dubé syndrome, the overall prognosis is based upon the severity of the signs and symptoms of the associated genetic disorder

Additional and Relevant Useful Information for Oncocytoma of Kidney:

Please visit our Cancer & Benign Tumors Health Center for more physician-approved health information:

http://www.dovemed.com/diseases-conditions/cancer/