Necrotizing sialometaplasia (NS) is a benign,

ulcerative An ulcer is a discontinuity or break in a bodily membrane that impedes normal function of the affected organ. According to Robbins's pathology, "ulcer is the breach of the continuity of skin, epithelium or mucous membrane caused by sloughing o ...

lesion A lesion is any damage or abnormal change in the tissue of an organism, usually caused by disease or trauma. ''Lesion'' is derived from the Latin "injury". Lesions may occur in plants as well as animals. Types There is no designated classifi ...

, usually located towards the back of the

hard palate The hard palate is a thin horizontal bony plate made up of two bones of the facial skeleton, located in the roof of the mouth. The bones are the palatine process of the maxilla and the horizontal plate of palatine bone. The hard palate spans ...

. It is thought to be caused by ischemic

necrosis Necrosis () is a form of cell injury which results in the premature death of cells in living tissue by autolysis. Necrosis is caused by factors external to the cell or tissue, such as infection, or trauma which result in the unregulated dige ...

(death of tissue due to lack of blood supply) of minor salivary glands in response to

trauma Trauma most often refers to: *Major trauma, in physical medicine, severe physical injury caused by an external source *Psychological trauma, a type of damage to the psyche that occurs as a result of a severely distressing event *Traumatic inju ...

. Often painless, the condition is self-limiting and should heal in 6–10 weeks. Although entirely benign and requiring no treatment, due to its similar appearance to oral cancer, it is sometimes

misdiagnosed A medical error is a preventable adverse effect of care ("iatrogenesis"), whether or not it is evident or harmful to the patient. This might include an inaccurate or incomplete diagnosis or treatment of a disease, injury, syndrome, behavior, i ...

as malignant. Therefore, it is considered an important condition, despite its rarity.

Signs and symptoms

The condition most commonly is located at the junction of the hard and

soft palate The soft palate (also known as the velum, palatal velum, or muscular palate) is, in mammals, the soft tissue constituting the back of the roof of the mouth. The soft palate is part of the palate of the mouth; the other part is the hard palate. ...

. However, the condition may arise anywhere minor salivary glands are located.Minor salivary glands are found in most

mucosal A mucous membrane or mucosa is a membrane that lines various cavities in the body of an organism and covers the surface of internal organs. It consists of one or more layers of epithelial cells overlying a layer of loose connective tissue. It is ...

surfaces in the mouth, apart from the front third of the hard palate, the front third of the dorsal surface of the tongue, and the

attached gingiva "Attached" is the 160th episode of the American science fiction television series ''Star Trek: The Next Generation''. The eighth episode of the Star Trek: The Next Generation (season 7), seventh season. This explores the relationship between two c ...

. (see Hupp ''et al.'' 2013, p.395) It has also been occasionally reported to involve the major salivary glands. It may be present only on one side, or both sides. The lesion typically is 1–4 cm in diameter. Initially, the lesion is a tender, erythematous (red) swelling. Later, in the ulcerated stage, the overlying mucosa breaks down to leave a deep, well-circumscribed ulcer which is yellow-gray in color and has a lobular base. There is usually only minor pain, and the condition is often entirely painless. There may be prodromal symptoms similar to

flu Influenza, commonly known as "the flu", is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These symptom ...

before the appearance of the lesion.

Causes

The exact cause of the condition is unknown. There is most evidence to support vascular infarction and ischemic necrosis of salivary gland lobules as a mechanism for the condition. Experimentally,

local anaesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciousness, as opposed to a general an ...

injections and tying of the arteries is reported to trigger the development of tissue changes similar to NS in lab rats. Factors which are thought to cause this ischemia are listed below, however sometimes there is no evident predisposing factor or initiating event. * Trauma e.g. during intubation, or surgical procedures *

Local anesthetic A local anesthetic (LA) is a medication that causes absence of pain sensation. In the context of surgery, a local anesthetic creates an absence of pain in a specific location of the body without a loss of consciousness, as opposed to a general an ...

injection *

Smoking Smoking is a practice in which a substance is burned and the resulting smoke is typically breathed in to be tasted and absorbed into the bloodstream. Most commonly, the substance used is the dried leaves of the tobacco plant, which have bee ...

Alcohol Alcohol most commonly refers to: * Alcohol (chemistry), an organic compound in which a hydroxyl group is bound to a carbon atom * Alcohol (drug), an intoxicant found in alcoholic drinks Alcohol may also refer to: Chemicals * Ethanol, one of sev ...

Diabetes mellitus Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ap ...

Vascular disease Vascular disease is a class of diseases of the blood vessels – the arteries and veins of the circulatory system of the body. Vascular disease is a subgroup of cardiovascular disease. Disorders in this vast network of blood vessels can cause a ra ...

, (e.g.

arteriosclerosis Arteriosclerosis is the thickening, hardening, and loss of elasticity of the walls of Artery, arteries. This process gradually restricts the blood flow to one's organs and tissues and can lead to severe health risks brought on by atherosclerosis ...

) * Pressure from a dental prosthesis *

Allergy Allergies, also known as allergic diseases, refer a number of conditions caused by the hypersensitivity of the immune system to typically harmless substances in the environment. These diseases include hay fever, food allergies, atopic derma ...

* Bulimia *

Infection An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...

Ionizing radiation Ionizing radiation (or ionising radiation), including nuclear radiation, consists of subatomic particles or electromagnetic waves that have sufficient energy to ionize atoms or molecules by detaching electrons from them. Some particles can travel ...

Diagnosis

Differentiation between this and SCC would be based on a history of recent trauma or dental treatment in the area.

Immunohistochemistry Immunohistochemistry (IHC) is the most common application of immunostaining. It involves the process of selectively identifying antigens (proteins) in cells of a tissue section by exploiting the principle of antibodies binding specifically to an ...

may aid the diagnosis. If the lesion is NS, there will be focal to absent immunoreactivity for p53, low immunoreactivity for MIB1 ( Ki-67), and the presence of 4A4/ p63- and calponin-positive myoepithelial cells.

Treatment

No surgery is required.

Prognosis

Healing is prolonged, and usually takes 6–10 weeks. The ulcer heals by

secondary intention Wound healing refers to a living organism's replacement of destroyed or damaged tissue by newly produced tissue. In undamaged skin, the epidermis (surface, epithelial layer) and dermis (deeper, connective layer) form a protective barrier agains ...

Epidemiology

The condition is rare. The typical age range of those affected by the condition is about 23–66 years of age. It usually occurs in smokers. The male to female ratio has been reported as 1.95:1, and 2.31:1.

Signs and symptoms

Causes

Diagnosis

Treatment

Prognosis

Epidemiology

History

Notes

References

External links