Melanoma in Adult
The etiology of melanoma is incompletely understood, although ultraviolet radiation is believed to play a role in some melanomas and knowledge of the melanoma genome continues to advance. Melanoma has been shown to have one of highest mutation rates of any cancer type, reflective of its clinical and pathologic diversity and resistance to treatment in advanced stages.
Risk factors for melanoma include a family history or prior personal history of melanoma, a history of severe or blistering sunburns, a changing mole, a giant congenital nevus (greater than 20 cm), older age, lighter skin phototype, and multiple atypical nevi. In a case control study of over 1000 patients, 3 or more iris pigmented lesions conferred an increased risk for cutaneous melanoma. Men are more prone to developing melanoma on the head, neck, and trunk, whereas women tend to develop melanoma on the arms and legs. The median age at diagnosis is in the 60s. The number of new cases of melanoma in the United States has been steadily rising since 1975, with an estimated 76 380 new cases of melanoma in the United States in 2016. The lifetime risk of being diagnosed with melanoma in the United States is estimated to be 2.1%.
The primary prognostic feature of melanoma is the depth of invasion, which is measured histologically in millimeters and referred to as the Breslow thickness. Early diagnosis and treatment of thin melanomas can lead to a generally favorable prognosis (97% and 93% for 5- and 10-year survival for a T1aN0M0 melanoma; see staging below), while advanced forms carry a dismal prognosis (33% for 1-year survival for an M1c melanoma). Mortality rates are higher among men than among women. The most frequent sites of melanoma metastasis are skin / subcutaneous, lymph nodes, lungs, liver, and brain; however, melanoma can metastasize to any organ of the body.
The management of advanced melanoma has changed dramatically over the last several years and continues to rapidly evolve with the introduction of therapies targeted to specific genetic mutations and immunotherapies that activate an individual's immune system against melanoma. Clinical trials have shown these agents to be effective in extending life expectancy in metastatic melanoma for several months.
Related topic: Amelanotic melanoma
C43.9 – Malignant melanoma of skin, unspecified
372244006 – Malignant melanoma
- Atypical nevus
- Seborrheic keratosis – presence of pseudohorn cysts is typical
- Pigmented basal cell carcinoma – pearly quality
- Bowen disease (pagetoid or pigmented)
- Spitz nevus
- Compound nevus
- Congenital nevus
- Blue nevus
- Lentigo simplex
- Solar lentigo
- Lobular capillary hemangioma (pyogenic granuloma) – friable, glistening surface
- Hemangioma – cherry, thrombosed
- Dermatofibroma – firm tan or brown papule with positive dimple sign
- Halo nevus – tan or brown papule with surrounding depigmented patch
- Metastatic carcinoma
- Paget disease
- Tinea nigra
- Subungual hematoma
- Pigmented actinic keratosis
- Talon noir (black heel)
- Longitudinal melanonychia (a pigmented line along the length of a nail plate) may be a benign finding or a sign of a nail matrix melanoma. Hutchinson's sign – the presence of pigment in the proximal nail fold in a patient with longitudinal melanonychia – should prompt consideration of a nail matrix melanoma.
- Recurrent melanocytic nevus – History of the initial biopsy is often critical for the dermatologist and/or pathologist. Recurrent nevi characteristically occur on the trunk within 6 months of the original biopsy in women 20-30 years of age. While many different clinical morphologies may be seen, it often manifests as a scar with variegated hyper- or hypopigmentation, linear streaking, and halo, stippled, and/or diffuse pigmentation patterns. While most cases do not pose a diagnostic challenge on histopathology, some specimens, especially partial biopsies, may look indistinguishable from melanoma on histopathologic grounds alone.