What Is a Mucosal Neuroma?

A mucosal neuroma is a tumor of the facial nerves that appears on the mucous membranes—that is, soft areas of the skin such as those inside the mouth, on and around the lips, and under the eyelids. Although mucosal neuromas themselves are not cancerous, their appearance is often associated with certain kinds of cancer.

Appearance

• A mucosal neuroma is usually between 0.08 inch and 0.28 inch in diameter.

  A mucosal neuroma appears as a round, yellow-white, painless nodule between two and seven millimeters in diameter (about the size of a small pencil eraser). Singular mucosal neuromas sometimes appear, but more commonly they show up in clusters. Large numbers of mucosal neuromas originating deep in the connective tissue of the skin can cause overall swelling of the lips, cheeks and eyelids as well as the characteristic bumps on the skin surface.

Multiple Endocrine Neoplasm Type 2B

• A cluster of mucosal neuromas may indicate a larger problem.

  Very commonly, the appearance of multiple mucosal neuromas is associated with a DNA mutation that also causes cancer of the thyroid, adrenal glands and other components of the endocrine system. The cluster of diseases presented by patients with this mutation is called multiple endocrine neoplasm type 2B—or MEN-2B—and is a fast-progressing condition that becomes apparent between infancy and puberty. Multiple mucosal neuromas are often an early symptom that leads to diagnosis. MEN-2B patients have distinctive physical traits, including an elongated face, prominent jaw and eyebrows, and loose joints, and they are usually tall with long arms and legs. This group of physical traits, collectively called a "marfanoid" appearance, has sometimes been attributed to Abraham Lincoln, and a recent book, "The Physical Lincoln," suggests that he may have suffered from MEN-2B.

Pure Mucosal Neuroma Syndrome

• Most, but not all, patients with mucosal neuromas have MEN-2B.

  Although all patients with MEN-2B have mucosal neuromas, not all patients with mucosal neuromas have MEN-2B. Four cases of "pure" mucosal neuromal syndrome—or MNS—in which the patient did not have the DNA mutation associated with MEN-2B were documented in a 1998 article in "The Journal of Clinical Endocrinology & Metabolism," and a 2004 case study in the "British Journal of Oral and Maxillofacial Surgery" reported on a patient with a solitary mucosal neuroma but no other symptoms of MEN-2B. Approximately 95 percent of patients with mucosal neuromas, however, are eventually diagnosed with MEN-2B.

Incidence and Treatment

• Mucosal neuromas and MEN-2 are considered rare, with about one in 30,000 individuals affected, according to "Essentials of Anatomic Pathology." Usually the patient's first neuromas are seen by age 10. The growths themselves are benign and surgical removal is not considered necessary. If the patient has the genetic mutation associated with MEN-2B, immediate surgical removal of the thyroid gland is often recommended because of the very high chance of early-onset thyroid cancer.

Similar Neuromas

• Though similar in appearance, PENs and neurofibromas have different implications for the patient's health.

  Any tumor that involves the peripheral nervous tissue is a neuroma. Mucosal neuromas can be similar in appearance to other neuromas, especially plexiform neurofibromas, which are indicative of a less aggressive disease called neurofibromatosis I, and palisaded encapsulated neuromas, which are not indicative of any systemic disease. Because the treatment and prognosis for these different neuromas are drastically different, it is important to differentiate between them clinically.

Identification

• Mucosal neuromas can be differentiated from other neuroma types in several ways. Mucosal neuromas and neurofibromas usually first appear in young children or adolescents, whereas PENs are usually seen in older patients. Physicians can sometimes identify a neuroma as a mucosal neuroma if other symptoms of MEN-2B are obvious or if the patient has been positively identified as having the associated genetic mutation. The changes in the underlying tissue also differ between the neuromas, so examining a biopsy sample of the growth under the microscope can help with differentiation. Histologically, a mucosal neuroma is characterized by overgrowth of multiple components of the nerve fiber, especially the connective tissue that surrounds individual nerves, called the perineurium.