Melanoma overview

Overview
Melanoma is a malignant tumor of melanocytes which are found predominantly in skin but also in the bowel and the eye (see uveal melanoma). It is one of the rarer types of skin cancer but causes the majority of skin cancer related deaths. Despite many years of intensive laboratory and clinical research, the sole effective cure is surgical resection of the primary tumor before it achieves a thickness greater than 1 mm.

Around 160,000 new cases of melanoma are diagnosed worldwide each year, and it is more frequent in males and caucasians. It is more common in caucasian populations living in sunny climates than other groups. According to the WHO Report about 48,000 melanoma related deaths occur worldwide per annum.

The treatment includes surgical removal of the tumor; adjuvant treatment; chemo- and immunotherapy, or radiation therapy.

Melanomas also occur in horses, see equine melanoma.

Sometimes the skin lesion may bleed, itch, or ulcerate, although this is a very late sign. A slow-healing lesion should be watched closely, as that may be a sign of melanoma. Be aware also that in circumstances that are still poorly understood, melanomas may "regress" or spontaneously become smaller or invisible - however the malignancy is still present. Amelanotic (colorless or flesh-colored) melanomas do not have pigment and may not even be visible. Lentigo maligna, a superficial melanoma confined to the topmost layers of the skin (found primarily in older patients) is often described as a "stain" on the skin. Some patients with metastatic melanoma do not have an obvious detectable primary tumor.

Types of primary melanoma


The most common types of Melanoma in the skin: Any of the above types may produce melanin (and be dark in colour) or not (and be amelanotic - not dark). Similarly any subtype may show desmoplasia (dense fibrous reaction with neurotropism) which is a marker of aggressive behaviour and a tendency to local recurrence.
 * superficial spreading melanoma (SSM)
 * nodular melanoma
 * acral lentiginous melanoma
 * lentigo maligna (melanoma)

Elsewhere:
 * clear cell sarcoma (Melanoma of Soft Parts)
 * mucosal melanoma
 * uveal melanoma

Equine melanoma
Melanomas are also not uncommon in horses, being largely confined to grey (or white) animals - 80% of such pale horses will develop melanomata by 15 years of age ; of these, 66% are slow growing but all may be classified as malignant. Surgical excision may be attempted in some cases, if the tumours are limited in extent and number. However, they are often multiple (especially in older animals) and perineal tumours are notoriously difficult to excise. Often, a position of "benign neglect" is assumed, especially if the tumours are not causing any clinical problems. Medical therapy with cimetidine (2.5-4.0mg/kg three times daily for 2 months or more) is also an option, although it has a lower success rate than surgery and cryosurgery.

Treatment of advanced malignant melanoma is performed from a multidisciplinary approach including dermatologists, medical oncologists, radiation oncologists, surgical oncologists, general surgeons, plastic surgeons, neurologists, neurosurgeons, otorhinolaryngologists, radiologists, pathologists/dermatopathologists, research scientists, nurse practitioners and physician assistants, and palliative care experts. Nurse practitioners (NPs) and physician assistants (PAs) are qualified to evaluate and treat patients on behalf of their supervising physicians. Treatment guidelines can be found through many resources available to health care professionals around the world. Inspired by melanoma’s increasing prevalence, researchers are seeking to understand the pathways that regulate melanin production.