Ceruminous adenoma are rare tumors, accounting for less than 1% of all external ear tumors. The patients will present with a mass, perhaps associated pain, and may have changes in hearing (usually a sensorineural or a conductive hearing loss). Some patients have tinnitus. Nerve paralysis is very uncommon.

An adenoma of a parathyroid gland may secrete inappropriately high amounts of parathyroid hormone and thereby cause primary hyperparathyroidism.

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.

Bronchial adenomas are adenomas in the bronchi. They may cause carcinoid syndrome, a type of paraneoplastic syndrome.

The colorectal adenoma is a benign glandular tumor of the colon and the rectum. It is a precursor lesion of the colorectal adenocarcinoma (colon cancer).

Some morphological variants have been described:

- tubular adenoma

- tubulovillous adenoma

- villous adenoma

- sessile serrated adenoma (SSA)

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.

A ceruminous adenoma (also known as adenoma of the ceruminous gland and ceruminoma) is a benign glandular neoplasm which arises from the ceruminous glands located within the external auditory canal. These glands are found within the outer one third to one half of the external auditory canal, more common along the posterior surface; therefore, the tumor develops within a very specific location.

The signs and symptoms are similar to other malignant salivary gland tumours; however, it may have been preceded by an appreciable mass that was long-standing and did not appear to be growing.

Findings that suggest a malignant salivary gland tumour include rapid growth, facial weakness (due to facial nerve compression), pain, skin ulceration, fixation of the mastoid tip

and parasthesias.

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.

Salivary gland tumours usually present as a lump or swelling in the affected gland which may or may not have been present for a long time. The lump may be accompanied by symptoms of duct blockage (e.g. xerostomia). Usually, in their early stages it is not possible to distinguish a benign tumour from a malignant one. One of the key differentiating symptoms of a malignant growth is nerve involvement. For example signs of facial nerve damage (e.g facial palsy) are associated with malignant parotid tumours. Facial pain, and paraesthesia are also very often associated with a malignant tumours. Other red flag symptoms which may suggest malignancy and warrant further investigation are fixation of the lump to the overlying skin, ulceration and induration of the mucosa.

Due to the diverse nature of salivary gland tumours, many different terms and classification systems have been used. Perhaps the most widely used currently is that system proposed by the World Health Organization in 2004, which classifies salivary neoplasms as primary or secondary, benign or malignant, and also by tissue of origin. This system defines five broad categories of salivary gland neoplasms:

Benign epithelial tumors

- Pleomorphic adenoma

- Warthin's tumor

- Myoepithelioma

- Basal cell adenoma

- Oncocytoma

- Canalicular adenoma

- Lymphadenoma

- "Sebaceous lymphadenoma"

- "Nonsebaceous lymphadenoma"

- Ductal papilloma

- "Inverted ductal papilloma"

- "Intraductal papilloma"

- "Sialadenoma papilliferum"

- Cystadenoma

- Malignant epithelial tumors

- Acinic cell carcinoma

- Mucoepidermoid carcinoma

- Adenoid cystic carcinoma

- Polymorphous low-grade adenocarcinoma

- Epithelial-myoepithelial carcinoma

- Clear cell carcinoma, not otherwise specified

- Basal cell adenocarcinoma

- Sebaceous carcinoma

- Sebaceous lymphadenocarcinoma

- Cystadenocarcinoma

- Low-grade cribriform cystadenocarcinoma

- Mucinous adenocarcinoma

- Oncocytic carcinoma

- Salivary duct carcinoma

- Salivary duct carcinoma, not otherwise specified

- Adenocarcinoma, not otherwise specified

- Myoepithelial carcinoma

- Carcinoma ex pleomorphic adenoma

- Mammary analogue secretory carcinoma

- Carcinosarcoma

- Metastasizing pleomorphic adenoma

- Squamous cell carcinoma

- Large cell carcinoma

- Lymphoepithelial carcinoma

- Sialoblastoma

- Soft tissue tumors

- Hemangioma

- Hematolymphoid tumors

- Hodgkin lymphoma

- Diffuse large B-cell lymphoma

- Extranodal marginal zone B cell lymphoma

- Secondary tumors (i.e. a tumor which has metastasized to the salivary gland from a distant location)

Others, not included in the WHO classification above, include:

- Intraosseous (central) salivary gland tumors

- Hybrid tumors (i.e. a tumor displaying combined forms of histologic tumor types)

- Hybrid carcinoma

- Others

- Others

- Keratocystoma

- Sialolipoma

Pain is the most common symptom, followed by either sensorineural or conductive hearing loss, tinnitus or drainage (discharge). A mass lesion may be present, but it is often slow growing.

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).

SSAs, generally, are asymptomatic. They are typically identified on a colonoscopy and excised for a definitive diagnosis and treatment.

Most patients present clinically with progressive, one sided hearing loss, much more often of the sensorineural rather than conductive type. Patients may also experience tinnitus, vertigo, and loss of vestibular function (ataxia). Symptoms are usually present for a long time, which supports the slow growth of these tumors. Patients may also present with other symptoms related to von Hippel-Lindau syndrome in other anatomic sites, which will result in imaging evaluation of the head.

The tumor is usually solitary and presents as a slow growing, painless, firm single nodular mass. Isolated nodules are generally outgrowths of the main nodule rather than a multinodular presentation. It is usually mobile unless found in the palate and can cause atrophy of the mandibular ramus when located in the parotid gland. When found in the parotid tail, it may present as an eversion of the ear lobe. Though it is classified as a benign tumor, pleomorphic adenomas have the capacity to grow to large proportions and may undergo malignant transformation, to form carcinoma ex-pleomorphic adenoma, a risk that increases with time (9.5% chance to convert into malignancy in 15 years). Although it is "benign" the tumor is aneuploid, it can recur after resection, it invades normal adjacent tissue and distant metastases have been reported after long (+10 years) time intervals.

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.

SSAs are diagnosed by their microscopic appearance; histomorphologically, they are characterized by (1) basal dilation of the crypts, (2) basal crypt serration, (3) crypts that run horizontal to the basement membrane (horizontal crypts), and (4) crypt branching. The most common of these features is basal dilation of the crypts.

Unlike traditional colonic adenomas (e.g. tubular adenoma, villous adenoma), they do not (typically) have nuclear changes (nuclear hyperchromatism, nuclear crowding, elliptical/cigar-shaped nuclei).

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.

Nipple adenomas may be felt as a lump under the nipple or areola. They may come to attention because of nipple pain, ulceration, swelling or discharge.

This tumor only affects the outer 1/3 to 1/2 of the external auditory canal as a primary site. If this area is not involved, the diagnosis should be questioned. The most common tumor type is ceruminous adenoid cystic carcinoma and ceruminous adenocarcinoma, NOS.

Warthin's tumor primarily affects older individuals (age 60–70 years). There is a slight male predilection according to recent studies. The tumor is slow growing, painless, and usually appears in the tail of the parotid gland near the angle of the mandible. In 5–14% of cases, Warthin's tumor is bilateral, but the two masses usually are at different times. Warthin's tumor is highly unlikely to become malignant.

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.

The gland most likely affected is the parotid gland. In fact, it is the only tumor virtually restricted to the parotid gland. Though much less likely to occur than pleomorphic adenoma, Warthin's tumor is the second most common benign parotid tumor.

Focal nodular hyperplasia's most recognizable gross feature is a central stellate scar seen in 60–70% of cases. Microscopically, a lobular proliferation of bland-appearing hepatocytes with a bile ductular proliferation and malformed vessels within the fibrous scar is the most common pattern. Other patterns include telangiectatic, hyperplastic-adenomatous, and lesions with focal large-cell dysplasia. Rarely, these lesions may be multiple or can occur as part of a syndrome with hemangiomas, epithelioid hemangioendothelioma, hepatic adenomas, fibrolamellar hepatocellular carcinoma, vascular malformations of the brain, meningiomas, and/or astrocytomas.