Renal oncocytomas are often asymptomatic and are frequently discovered by chance on a CT or ultrasound of the abdomen. Possible signs and symptoms of a renal oncocytoma include blood in the urine, flank pain, and an abdominal mass.

Kidney tumours may be discovered on medical imaging incidentally (i.e. an incidentaloma), or may be present in patients as an abdominal mass or kidney cyst, hematuria, abdominal pain, or manifest first in a paraneoplastic syndrome that seems unrelated to the kidney.

Renal medullary fibroma, also renomedullary interstitial cell tumour and medullary fibroma, is a benign kidney tumour. It is commonly an incidental finding.

Renal medullary fibromas are diagnosed by pathologists based on the examination of tissue.

They consist of bland spindle-shaped or stellate-shaped cells in a loose stroma. Renal tubules may be entrapped.

Kidney tumours (or kidney tumors), also known as renal tumours, are tumours, or growths, on or in the kidney. These growths can be benign or malignant (kidney cancer).

Renal oncocytoma is thought to arise from the intercalated cells of collecting ducts of the kidney. It represent 5% to 15% of surgically resected renal neoplasms. Ultrastructurally, the eosinophilic cells have numerous mitochondria.

By hypersecretion of renin, JCT causes hypertension, often severe and usually sustained but occasionally paroxysmal, and secondary hyperaldosteronism inducing hypokalemia, though the later can be mild despite high renin. Both of these conditions may be corrected by surgical removal of the tumor. Asymptomatic cases have been reported.

Cystic nephromas are often asymptomatic. They are typically discovered on medical imaging incidentally (i.e. an incidentaloma).

Historically, medical practitioners expected a person to present with three findings. This classic triad is 1: haematuria, which is when there is blood present in the urine, 2: flank pain, which is pain on the side of the body between the hip and ribs, and 3: an abdominal mass, similar to bloating but larger. It is now known that this classic triad of symptoms only occurs in 10–15% of cases, and is usually indicative that the renal cell carcinoma (RCC) is in an advanced stage. Today, RCC is often asymptomatic (meaning few to no symptoms) and is generally detected incidentally when a person is being examined for other ailments.

Other signs and symptom may include haematuria; loin pain; abdominal mass; malaise, which is a general feeling of unwellness; weight loss and/or loss of appetite; anaemia resulting from depression of erythropoietin; erythrocytosis (increased production of red blood cells) due to increased erythropoietin secretion; varicocele, which is seen in males as an enlargement of the pampiniform plexus of veins draining the testis (more often the left testis) hypertension (high blood pressure) resulting from secretion of renin by the tumour; hypercalcemia, which is elevation of calcium levels in the blood; sleep disturbance or night sweats; recurrent fevers; and chronic fatigue.

Nephrogenic adenoma, also mesonephric adenoma and nephrogenic metaplasia, is a benign growth typically found in the urinary bladder.

It is thought to result from displacement and implantation of renal tubular cells, as this entity in kidney transplant recipients has been shown to be kidney donor derived.

This entity should not be confused with the similar-sounding "metanephric adenoma".

JCT is morphologically characterized by multiple foci malignant mesenchymal epithelioid cells with, often with admixed necrosis, and a perivascular growth pattern. The immunophenotype is rather characteristic, as the neoplastic cells express renin, CD34, smooth muscle actin, CD138, vimentin, collagen IV and is negative for cytokeratins as well as for S100, c-Kit and desmin.

The symptoms may be similar to those classically associated with renal cell carcinoma, and may include polycythemia, abdominal pain, hematuria and a palpable mass. Mean age at onset is around 40 years with a range of 5 to 83 years and the mean size of the tumour is 5.5 cm with a range 0.3 to 15 cm (1). Polycythemia is more frequent in MA than in any other type of renal tumour. Of further relevance is that this tumour is more commonly calcified than any other kidney neoplasm. Surgery is curative and no other treatment is recommended. There is so far no evidence of metastases or local recurrence.

Renal cell carcinoma (RCC) is a kidney cancer that originates in the lining of the proximal convoluted tubule, a part of the very small tubes in the kidney that transport primary urine. RCC is the most common type of kidney cancer in adults, responsible for approximately 90–95% of cases.

Initial treatment is most commonly either partial or complete removal of the affected kidney(s). Where the cancer has not metastasised (spread to other organs) or burrowed deeper into the tissues of the kidney, the 5-year survival rate is 65–90%, but this is lowered considerably when the cancer has spread.

The body is remarkably good at hiding the symptoms and as a result people with RCC often have advanced disease by the time it is discovered. The initial symptoms of RCC often include blood in the urine (occurring in 40% of affected persons at the time they first seek medical attention), flank pain (40%), a mass in the abdomen or flank (25%), weight loss (33%), fever (20%), high blood pressure (20%), night sweats and generally feeling unwell. When RCC metastasises, it most commonly spreads to the lymph nodes, lungs, liver, adrenal glands, brain or bones. Immunotherapy and targeted therapy have improved the outlook for metastatic RCC.

RCC is also associated with a number of paraneoplastic syndromes (PNS) which are conditions caused by either the hormones produced by the tumour or by the body's attack on the tumour and are present in about 20% of those with RCC. These syndromes most commonly affect tissues which have not been invaded by the cancer. The most common PNSs seen in people with RCC are: high blood calcium levels, polycythaemia (the opposite of anemia, due to an overproduction of the hormone erythropoietin), thrombocytosis (too many platelets in the blood, leading to an increased tendency for blood clotting and bleeds) and secondary amyloidosis.

Metanephric adenoma (MA)is a rare, benign tumour of the kidney, that can have a microscopic appearance similar to a nephroblastoma (Wilms tumours), or a papillary renal cell carcinoma.

It should not be confused with the pathologically unrelated, yet similar sounding, "mesonephric adenoma".

Nephrogenic adenomas are diagnosed under the microscope by pathologists. Microscopically the tumor shows closely packed small tubular structures in edematous stroma. The tubules show considerable variation in size and shape resembling convoluted tubules of the kidney. The single layer of cells lining the tubules are cuboidal with a scant to moderate amount of cytoplasm. In some areas they may have a hobnail appearance.

People over 20 years of age with Birt–Hogg–Dubé syndrome have an increased risk of developing slow-growing kidney tumors (chromophobe renal carcinoma and renal oncocytoma, respectively), kidney cysts, and possibly tumors in other organs and tissues. These tumors often occur in both kidneys and in multiple locations in each kidney. The average number of kidney tumors found in a person with BHD is 5.3, though up to 28 tumors have been found. Hybrid oncocytoma/chromophobe carcinoma, found in 50% of cases, is the most commonly found cancer, followed by chromophobe renal carcinoma, clear cell renal carcinoma, renal oncocytoma, and papillary renal cell carcinoma. People over 40 years old and men are more likely to develop kidney tumors, which are diagnosed at a median age of 48. Kidney cancer associated with BHD have been diagnosed in people at ages as young as 20.

In general, people with Birt–Hogg–Dubé syndrome are at roughly seven times the risk of kidney cancer compared to the unaffected population. Estimates of the incidence among people with the disease range from 14%–34%. Rarely, it is associated with clear cell renal cell carcinoma and papillary renal cell carcinoma. If it develops in someone with BHD, renal cell carcinoma occurs later in life and has a poor prognosis. Though the types of tumor typically associated with BHD are considered less aggressive, cases of advanced or metastatic kidney cancer have been observed in people with the syndrome. Both benign and cancerous tumors can reduce kidney function over time as they grow larger.

Birt–Hogg–Dubé syndrome affects the skin and increases the risk of tumors in the kidneys and lungs. The condition is characterized by multiple noncancerous dome-shaped tumors of the hair follicles (fibrofolliculomas), particularly on the face, neck, and—more rarely—the upper chest. The fibrofolliculomas are generally described as having an opaque white color or a yellowish tone and have a waxy, smooth texture. The tumors are always found on and around the nose and on and behind the outer ear. Typically, they first appear in a person's 20s or 30s, and are found in more than 80% of people with the syndrome above the age of 40. The tumors become larger and more numerous over time. Tumors differ between individuals: they may appear merged in plaques, look similar to a comedo with a plug of keratin, or include epidermoid cysts. A large number of tumors on the face can be associated with hyperseborrhea (abnormally elevated sebum production). The presence of fibrofolliculomas on a person's face can cause significant psychological distress.

Other tumors can include trichodiscomas (tumors of the hair disc, which may be identical to fibrofolliculomas), angiofibromas, and perifollicular fibromas. However, angiofibromas are more common in tuberous sclerosis. Along with the tumors, other skin conditions are seen in people with Birt–Hogg–Dubé syndrome. Approximately 40% of people or families with the disease have papules in their mouth, which can be located on the cheeks (buccal mucosa), tongue, gums, or lips. Either white or mucosa-colored, they are discrete, small, and soft and consist of fibrous tissue covered in thickened epithelium. Collagenomas of the skin are also found in some families. Many people with BHD have skin lesions that appear to be acrochordons (skin tags), but may instead be fibrofolliculomas. These lesions are usually found in the armpit, on the eyelids, and in folds of skin. Not all individuals develop the facial tumors; some families with the mutation that causes BHD develop only kidney tumors or spontaneous pneumothorax.

A cystic nephroma, also known as multilocular cystic nephroma, mixed epithelial stromal tumour (MEST) and renal epithelial stromal tumour (REST), is a type of rare benign kidney tumour.

If the dilated blood vessels in an angiomyolipoma rupture, the resulting retroperitoneal haemorrhage causes sudden pain, accompanied with nausea and vomiting. When the patient presents in the emergency department, up to 20% will be in shock.

Angiomyolipomas are the most common benign tumour of the kidney. Although regarded as benign, angiomyolipomas may grow such that kidney function is impaired or the blood vessels may dilate and burst leading to bleeding.

Angiomyolipomas are strongly associated with the genetic disease tuberous sclerosis, in which most individuals will have several angiomyolipomas affecting both kidneys. They are also commonly found in women with the rare lung disease lymphangioleiomyomatosis. Angiomyolipomas are less commonly found in the liver and rarely in other organs. Whether associated with these diseases or sporadic, angiomyolipomas are caused by mutations in either the TSC1 or TSC2 genes, which govern cell growth and proliferation. They are composed of blood vessels, smooth muscle cells and fat cells.

Large angiomyolipoma can be treated with embolisation. Drug therapy for angiomyolipoma is at the research stage. The Tuberous Sclerosis Alliance has published guidelines on diagnosis, surveillance and management.

Most patients experience moderate to severe hypercalcemia and high parathyroid hormone levels. A large mass in the neck is often seen, and renal and bone abnormalities are common.

Salivary gland oncocytomas are most common in ages 70–80, females, the parotid gland (85–90%), and are firm, slowly growing, painless masses of less than 4 cm. They may be bilateral.

About 25–50% of hepatic adenomas cause pain in the right upper quadrant or epigastric region of the abdomen. Since hepatic adenomas can be large (8–15 cm), patients may notice a palpable mass. However, hepatic adenomas are usually asymptomatic, and may be discovered incidentally on imaging ordered for some unrelated reason. Large hepatic adenomas have a tendency to rupture and bleed massively inside the abdomen. If not treated, there is a 30% risk of bleeding. Bleeding may lead to hypotension, tachycardia, and sweating (diaphoresis).

An oncocytoma is an epithelial tumor composed of oncocytes, large eosinophilic cells having small, round, benign-appearing nuclei with large nucleoli.

Oncocytoma can arise in a number of organs.

Parathyroid carcinoma is a rare malignant neoplasm resulting in parathyroid adenoma to carcinoma progression. It forms in tissues of one or more of the parathyroid glands (four pea-sized glands in the neck that make parathyroid hormone, which helps the body store and use calcium).

It is rare, and much less common than parathyroid adenoma.

It can be difficult to excise.