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.

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.

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.

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.

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.

A adrenocortical adenoma (or adrenal cortical adenoma, or sometimes simply adrenal adenoma) is a benign tumor of the adrenal cortex.

It can present with Cushing's syndrome or primary aldosteronism. They may also secrete androgens, causing hyperandrogenism. Also, they are often diagnosed incidentally as incidentalomas.

Is a well circumscribed, yellow tumour in the adrenal cortex, which is usually 2–5 cm in diameter. The color of the tumour, as with adrenal cortex as a whole, is due to the stored lipid (mainly cholesterol), from which the cortical hormones are synthesized. These tumors are frequent incidental findings at post mortem examination, and appear to have produced no significant metabolic disorder; only a very small percentage lead to Cushing's syndrome. Nevertheless, these apparently non-functioning adenomas are most often encountered in elder obese people. There is some debate that they may really represent nodules in diffuse nodular cortical hyperplasia.

Very occasionally, a true adrenal cortical adenoma is associated with the clinical manifestations of Conn's syndrome, and can be shown to be excreting mineralocorticoids.

A thyroid adenoma is distinguished from a multinodular goiter of the thyroid in that an adenoma is typically solitary, and is a neoplasm resulting from a genetic mutation (or other genetic abnormality) in a single precursor cell. In contrast, a multinodular goiter is usually thought to result from a hyperplastic response of the entire thyroid gland to a stimulus, such as iodine deficiency.

Careful pathological examination may be necessary to distinguish a thyroid adenoma from a minimally invasive follicular thyroid carcinoma.

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.

A parathyroid adenoma is a benign tumor of the parathyroid gland. It generally causes hyperparathyroidism; there are very few reports of parathyroid adenomas that were not associated with hyperparathyroidism.

A human being usually has four parathyroid glands located on the back surface of the thyroid in the neck. The parathyroids secrete parathyroid hormone (PTH), which increases the concentration of calcium in the blood by inducing the bones to release calcium into the blood and the kidneys to reabsorb it from the urine into the blood. When a parathyroid adenoma causes hyperparathyroidism, more parathyroid hormone is secreted, causing the calcium concentration of the blood to rise, resulting in hypercalcemia.

Parathyroid adenoma can be associated with overexpression of the cyclin D1 gene.

A parathyroid neoplasm is a tumor of the parathyroid gland.

Types include:

- Parathyroid adenoma

- Parathyroid carcinoma

Pituitary adenomas are seen in 10% of neurological patients. A lot of them remain undiagnosed. Treatment is usually surgical, to which patients generally respond well. The most common subtype, prolactinoma, is seen more often in women, and is frequently diagnosed during pregnancy as the hormone progesterone increases its growth. Medical therapy with cabergoline or bromocriptine generally suppresses prolactinomas; progesterone antagonist therapy has not proven to be successful.

Adenomas of the anterior pituitary gland are a major clinical feature of multiple endocrine neoplasia type 1 (MEN1), a rare inherited endocrine syndrome that affects 1 person in every 30,000. MEN causes various combinations of benign or malignant tumors in various glands in the endocrine system or may cause the glands to become enlarged without forming tumors. It often affects the parathyroid glands, pancreatic islet cells, and anterior lobe of the pituitary gland. MEN1 may also cause non-endocrine tumors such as facial angiofibromas, collagenomas, lipomas, meningiomas, ependymomas, and leiomyomas. Approximately 25 percent of patients with MEN1 develop pituitary adenomas.

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.

Parathyroid carcinoma is sometimes diagnosed during surgery for primary hyperparathyroidism. If the surgeon suspects carcinoma based on severity or invasion of surrounding tissues by a firm parathyroid tumor, aggressive excision is performed, including the thyroid and surrounding tissues as necessary.

Agents such as calcimimetics (for example, cinacalcet) are used to mimic calcium and are able to activate the parathyroid calcium-sensing receptor (making the parathyroid gland "think" we have more calcium than we actually do), therefore lowering the calcium level, in an attempt to decrease the hypercalcemia.

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.

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.

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

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.

Syringocystadenoma papilliferum (also known as "syringadenoma papilliferum") is a benign apocrine tumor.

It can arise with nevus sebaceus.

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

Papillary eccrine adenoma (also known as "tubular apocrine adenoma") is a cutaneous condition characterized by an uncommon benign sweat gland neoplasm that presents as a dermal nodule located primarily on the extremities of black patients.

A sebaceous adenoma, a type of adenoma, a cutaneous condition characterized by a slow-growing tumor usually presenting as a pink, flesh-coloured, or yellow papule or nodule.

Little is known about the total incidence of salivary gland tumours as most benign tumours go unrecorded in national cancer registries. The majority of salivary tumours are benign (65-70%). Within the parotid gland 75 - 80% of tumours are benign. Around 50% of the tumours found in the submandibular glands are benign. Sublingual gland tumours are very rare but if present, they are most likely to be malignant.

In the United States, salivary gland cancers are uncommon with an incidence rate of 1.7 in 100000 between 2009 and 2013.

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.