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.

Malignant transformation to squamous cell carcinoma may occur, but is unusual.

Swelling is the most common presenting complaint; however, OKCs may be asymptomatic and found incidentally on dental X-rays.

Polymorphous low-grade adenocarcinoma, often abbreviated PLGA, is a rare, asymptomatic, slow-growing malignant salivary gland tumor. It is most commonly found in the palate.

The name of the tumor derives from the fact that:

- It has a varied microscopic architectural appearance, i.e. it is "polymorphous".

- It is non-aggressive when compared to other oral cavity tumors, i.e. it is a "low-grade" tumor.

- It forms glands, i.e. it is an "adenocarcinoma".

It affects the minor salivary glands in the area between the hard and the soft palate. Male to female ratio is 3:1, and the average age is 56 years.

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

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.

Mucinous carcinoma is a type of cancer that arises from epithelial cells; these line certain internal organs and skin, and produce mucin (the main component of mucus).

When found within the skin, mucinous carcinoma is commonly a round, elevated, reddish, and sometimes ulcerated mass, usually located on the head and neck.

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.

PLGAs consist of a monomorphous cell population that has a varied histologic morphology.

Microscopically, its histology can be confused with an adenoid cystic carcinoma and a pleomorphic adenoma.

Epithelial-myoepithelial carcinoma, abbreviated EMCa, is a rare malignant tumour that typically arises in a salivary gland and consists of both an epithelial and myoepithelial component. They are predominantly found in the parotid gland

and represent approximately 1% of salivary gland tumours.

Hidradenoma (also known as acrospiroma, from "akral ""peripheral"" + spiroma ""epithelial tumor of sweat gland") refers to a benign adnexal tumor of the apical sweat gland. Another name for Hidradenoma is Cystadenoma and Hydrocystadenomas. These are 1–3 cm translucent blue cystic nodules.It usually presents as a single, small skin-colored lesion, and is considered distinct from the closely related poroma. Hidradenomas are often sub-classified based on subtle histologic differences, for example:

- clear-cell hidradenoma or acrospiroma

- nodular hidradenoma or acrospiroma

- solid-cystic hidradenoma

Discussion of sweat gland tumors can be difficult and confusing due to the complex classification and redundant terminology used to describe the same tumors. For example, acrospiroma and hidradenoma are synonymous, and sometimes the term "acrospiroma" is used to generally describe benign sweat gland tumors. In addition, a single lesion may contain a mixture of cell-types. There has also been a change in understanding about how tumors that were previously believed to strictly derive from specific sweat gland types may, in fact, derive from both eccrine "or" apocrine glands.

Hidradenomas are by definition benign, with malignant transformation very rare. When tumors show malignant characteristics, they are known as hidradenocarcinoma. Surgical excision is usually curative and local recurrences are rare, although malignant tumors may metastasize.

Reticulated seborrheic keratosis (also known as "Adenoid seborrheic keratosis") is a common benign cutaneous condition characterized by a skin lesion with a dull or lackluster surface, and with keratin cysts seen histologically.

EMCas are diagnosed by examination of tissue, e.g. a biopsy.

Its appearance is very similar to adenomyoepithelioma of the breast, which may be the same tumour at a different anatomical site.

The histologic differential diagnosis includes adenoid cystic carcinoma and pleomorphic adenoma.

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

Bowen's disease typically presents as a gradually enlarging, well-demarcated red colored plaque with an irregular border and surface crusting or scaling. Bowen's disease may occur at any age in adults, but is rare before the age of 30 years; most patients are aged over 60. Any site may be affected, although involvement of palms or soles is uncommon. Bowen's disease occurs predominantly in women (70–85% of cases). About 60–85% of patients have lesions on the lower leg, usually in previously or presently sun-exposed areas of skin.

This is a persistent, progressive, unelevated, red, scaly or crusted plaque which is due to an intraepidermal carcinoma and is potentially malignant. The lesions may occur anywhere on the skin surface, including on mucosal surfaces. Freezing, cauterization, or diathermy coagulation is often effective treatment. Pathomorphologic study of tissue sampling revealed: polymorphism of spiny epithelial cells has progressed into atypism; increased mitosis; giant and multinucleate cells; acanthosis; hyperkeratosis and parakeratosis; basal membrane and basal layer are retained.

Trichoepithelioma is a neoplasm of the adnexa of the skin. Its appearance is similar to basal cell carcinoma.

One form has been mapped to chromosome 9p21.

A variant of eccrine spiradenoma which can be multiple on the scalp and can coalesce to form a 'Turban' tumour. In pathology, a cylindroma is a tumour with nests of cells that resemble a cylinder in cross section.

Types include:

- Dermal eccrine cylindroma, a benign tumour of the skin

- Adenoid cystic carcinoma, a malignant tumour of the salivary gland

Adenoid cystic carcinoma (sometimes referred to as adenocyst, malignant cylindroma, adenocystic, adenoidcystic, ACC or AdCC.) is a rare type of cancer that can exist in many different body sites. This tumor most often occurs in the salivary glands, but it can also be found in many anatomic sites, including the breast, lacrimal gland, lung, brain, bartholin gland, trachea, and the paranasal sinuses.

It is the third most common malignant salivary gland tumor overall (after mucoepidermoid carcinoma and polymorphous low grade adenocarcinoma). It represents 28% of malignant submandibular gland tumors, making it the single most common malignant salivary gland tumor in this region. Patients may survive for years with metastases because this tumor is generally well-differentiated and slow growing. In a 1999 study of a cohort of 160 ACC patients, disease specific survival was 89% at 5 years but only 40% at 15 years, reflecting deaths from late-occurring metastatic disease.

It is important to correctly identify, as it can be confused with atypical ductal hyperplasia, cribriform ductal carcinoma in situ (DCIS), and adenoid cystic carcinoma.

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.

Epithelial-myoepithelial carcinoma of the lung (EMECL) is a very rare histologic form of malignant epithelial neoplasm ("carcinoma") arising from lung tissue.

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".

The lesion at the base of the keratin mound is benign in the majority of cases. Malignancy is present in up to 20% of cases, with squamous cell carcinoma being the most common type. The incidence of squamous cell carcinoma increases to 37% when the cutaneous horn is present on the penis. Tenderness at the base of the lesion is often a clue to the presence of a possible underlying squamous cell carcinoma.

Basophilic, bland cells similar to acinar cells. Growth pattern: solid - acinar cells, microcytic - small systic spaces mucinous or eosinophilic, papillary-cystic - large cystic lined by epithelium, follicular - similar to thyroid tissue.

These tumors which resemble serous acinar cells vary in their behavior from locally aggressive to blatantly malignant.

It can also appear in the breast. The pancreatic form of acinic cell carcinoma is a rare subtype of exocrine pancreatic cancer. Exocrine pancreatic cancers are the most common form of pancreatic cancer when compared to endocrine pancreatic cancer.

Acinic cell carcinomas arise most frequently in the parotid gland. Other sites of primary tumors have included the submandibular gland and other major and minor salivary glands. There have been rare cases of primary tumors involving the parapharyngeal space and the sublingual gland.

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.