While there is a wide age range at clinical presentation (12–85 years), most patients come to clinical attention at 55 years (mean). There is no gender difference.

A physician's response to detecting an adenoma in a patient will vary according to the type and location of the adenoma among other factors. Different adenomas will grow at different rates, but typically physicians can anticipate the rates of growth because some types of common adenomas progress similarly in most patients. Two common responses are removing the adenoma with surgery and then monitoring the patient according to established guidelines.

One common example of treatment is the response recommended by specialty professional organizations upon removing adenomatous polyps from a patient. In the common case of removing one or two of these polyps from the colon from a patient with no particular risk factors for cancer, thereafter the best practice is to resume surveillance colonoscopy after 5–10 years rather than repeating it more frequently than the standard recommendation.

An oncocytoma is a tumor made up of oncocytes, epithelial cells characterized by an excessive amount of mitochondria, resulting in an abundant acidophilic, granular cytoplasm. The cells and the tumor that they compose are often benign but sometimes may be premalignant or malignant.

This is a very rare tumor, since only about 1 in 35,000 to 40,000 people have VHL, of whom about 10% have endolymphatic sac tumors. Patients usually present in the 4th to 5th decades without an gender predilection. The tumor involves the endolymphatic sac, a portion of the intraosseous inner ear of the posterior petrous bone.

Parathyroid cancer occurs in midlife at the same rate in men and women.

Conditions that appear to result in an increased risk of parathyroid cancer include multiple endocrine neoplasia type 1, autosomal dominant familial isolated hyperparathyroidism and hyperparathyroidism-jaw tumor syndrome (which also is hereditary). Parathyroid cancer has also been associated with external radiation exposure, but, most reports describe an association between radiation and the more common parathyroid adenoma.

Its cause is unknown, but there is a strong association with cigarette smoking. Smokers are at 8 times greater risk of developing Warthin's tumor than the general population.

An endocrine gland neoplasm is a neoplasm affecting one or more glands of the endocrine system.

Examples include:

- Adrenal tumor

- Pituitary adenoma

The most common form is thyroid cancer.

Condition such as pancreatic cancer or ovarian cancer can be considered endocrine tumors, or classified under other systems.

Pinealoma is often grouped with brain tumors because of its location.

An adenoma (from Greek αδένας, "", "gland" + -ώμα, "", "tumor") (; plural adenomas or adenomata ) is a benign tumor of epithelial tissue with glandular origin, glandular characteristics, or both. Adenomas can grow from many glandular organs, including the adrenal glands, pituitary gland, thyroid, prostate, and others. Some adenomas grow from epithelial tissue in nonglandular areas but express glandular tissue structure (as can happen in familial polyposis coli). Although adenomas are benign, over time they may transform to become malignant, at which point they are called adenocarcinomas. Most adenomas do not transform. But even while benign, they have the potential to cause serious health complications by compressing other structures (mass effect) and by producing large amounts of hormones in an unregulated, non-feedback-dependent manner (causing paraneoplastic syndromes). Some adenomas are too small to be seen macroscopically but can still cause clinical symptoms.

Most individuals come to clinical attention during the 5th decade, although the age range is broad (20 to 80 years). There is an equal gender distribution.

Hürthle cell adenoma is a rare benign tumor, typically seen in women between the ages of 70 and 80 years old. This adenoma is characterized by a mass of benign Hürthle cells (Askanazy cells). Typically such a mass is removed because it is not easy to predict whether it will transform into the malignant counterpart, a subtype of follicular thyroid cancer called a Hürthle cell carcinoma.

The majority of hepatic adenomas arise in women aged 20–40, most of whom use oral contraceptives. Other medications which also alter circulating hormone levels, such as anabolic or androgenic steroids, barbituates, clomifene, have also been implicated as risk factors.

Incidence of adenomas may be increased in metabolic diseases, including tyrosinemia and type 1 diabetes mellitus, and glycogen storage diseases (types 1 and 3), as well as in beta-thalassemia and hemochromatosis.

Patients with thyroid oncocytomas present with a thyroid nodule, usually with normal thyroid function. If the tumor is big or invasive, there may be other symptoms such as difficulty swallowing or talking.

They generally have a good prognosis. In one larger study, the 5-year and 10-year survival were over 90% and 80% respectively.

Carcinomas that metastasize into the pituitary gland are uncommon and typically seen in the elderly, with lung and breast cancers being the most prevalent, In breast cancer patients, metastases to the pituitary gland occur in approximately 6-8% of cases.

Symptomatic pituitary metastases account for only 7% of reported cases. In those who are symptomatic Diabetes insipidus often occurs with rates approximately 29-71%. Other commonly reported symptoms include anterior pituitary dysfunction, visual field defects, headache/pain, and ophthalmoplegia.

Treatment may include the following:

- Surgery with or without radiation

- Radiotherapy

Fast neutron therapy has been used successfully to treat salivary gland tumors, and has shown to be significantly more effective than photons in studies treating unresectable salivary gland tumors.

- Chemotherapy

Birt-Hogg-Dubé Syndrome patients, families, and caregivers are encouraged to join the NIH Rare Lung Diseases Consortium Contact Registry. This is a privacy protected site that provides up-to-date information for individuals interested in the latest scientific news, trials, and treatments related to rare lung diseases.

Patients treated with complete surgical excision can expect an excellent long term outcome without any problems. Recurrences may be seen in tumors which are incompletely excised.

A parathyroid neoplasm is a tumor of the parathyroid gland.

Types include:

- Parathyroid adenoma

- Parathyroid carcinoma

There are three main treatments for Hürthle cell adenomas. Once the adenoma is detected most often the nodules removed to prevent the cells from later metastisizing. A total thyroidectomy is often performed, this results in a complete removal of the thyroid. Some patients may only have half of their thyroid removed, this is known as a thyroid lobectomy. Another treatment option includes pharmacological suppression of thyroid hormone. The thyroid gland is responsible for producing the thyroid hormones triiodothyronine (T3) and thyroxine (T4). Patients with suppressed thyroid function often require oral thyroid replacement (e.g. levothyroxine) in order to maintain normal thyroid hormone levels. The final treatment option is RAI abaltion (radioactive iodine ablation). This treatment option is used to destroy infected thyroid cells after total thyroidectomy. This treatment does not change prognosis of disease, but will diminish the recurrence rate. Also, Hürthle cells do not respond well to RAI. However, often doctors suggest this treatment to patients with Hürthle cell adenoma and Hürthle cell carcinoma because some Hürthle cells will respond and it will kill remaining tissue.

Most of these tumors are treated with surgical removal. It is non recurrent.

Hepatocellular adenoma (also known as hepatic adenoma or hepadenoma) is a rare, benign liver tumor. It most commonly occurs in people with elevated systemic levels of estrogen, classically in women taking estrogen-containing oral contraceptive medication.

Carney triad (CT) is characterized by the coexistence of three types of neoplasms, mainly in young women, including gastric gastrointestinal stromal tumor, pulmonary chondroma, and extra-adrenal paraganglioma. The underlying genetic defect remains elusive. CT is distinct from Carney complex, and the Carney-Stratakis syndrome.

Carcinoma ex pleomorphic adenoma, abbreviated ca ex PA, is a type of cancer typically found in the parotid gland. It arises from the benign tumour pleomorphic adenoma.

Its prognosis depends on the stage. Early tumour have essentially a benign behaviour.

Pleomorphic adenoma is a common benign salivary gland neoplasm characterised by neoplastic proliferation of parenchymatous glandular cells along with myoepithelial components, having a malignant potentiality. It is the most common type of salivary gland tumor and the most common tumor of the parotid gland. It derives its name from the architectural Pleomorphism (variable appearance) seen by light microscopy. It is also known as "Mixed tumor, salivary gland type", which describes its pleomorphic appearance as opposed to its dual origin from epithelial and myoepithelial elements.

Almost all thyroid adenomas are follicular adenomas. Follicular adenomas can be described as "cold", "warm" or "hot" depending on their level of function. Histopathologically, follicular adenomas can be classified according to their cellular architecture and relative amounts of cellularity and colloid into the following types:

- Fetal (microfollicular) - these have the potential for microinvasion. These consist of small, closely packed follicles lined with epithelium.

- colloid (macrofollicular) - these do "not" have any potential for microinvasion

- embryonal (atypical) - have the potential for microinvasion.

- Hürthle cell adenoma (oxyphil or oncocytic tumor) - have the potential for microinvasion.

- Hyalinizing trabecular adenoma

Papillary adenomas are very rare.