Malignant Melanoma & Subtypes

Melanoma- is a type of skin cancer that occurs in the cells that color the skin, called melanocytes.  A direct translation of the word is “a black tumor”.  It is not to be confused with the more common forms of squamous cell or basal cell skin cancers.  Melanoma is the more serious because it can spread to other parts of the body through the lymph system or the blood.  It is the leading cause of all skin cancer-related deaths. 

The Cause

One of the main risk factors appears to be exposure to UV radiation.   Those exposed to intense sun over a short period of time are more at risk for melanoma than people who have a more consistent daily exposure.  

CUTANEOUS MELANOMA-Seventy per-cent (70%) of melanomas are “superficial spreading”, meaning that they have a superficial radial growth phase before they mature/clone and begin to invade vertically.  The majority of melanomas could therefore potentially, at least in theory, be cured if they were diagnosed early enough and excised with adequate margins.  It is mostly the superficial spreading melanomas that are increasing in incidence globally.

Twenty per-cent (20%) of cutaneous melanomas are NODULAR MALIGNANT MELANOMA, and they do not have a radial growth phase, at all.  Instead, they start out with a vertical growth phase, which explains why they are more aggressive.

The other ten per-cent (10%) of the cutaneous melanomas include LENTIGINOUS MALIGNANT MELANOMA, a slow growing, extended radial growth phase, on sun exposed skin, mostly on the face and neck.

ACRAL LENTIGINOUS MELANOMA-found on the palms, soles and nail beds, also in Asians & African Americans; has a radial growth phase initially but diagnosis is often delayed, perhaps because it looks like a wart or fungus.

DEMOPLASTIC MALIGNANT MELANOMAS- a scar like lesion which delays diagnosis, is not very aggressive even though it starts to grow in the vertical growth phase, but may spread to the lungs.

GIANT MELANOCYTIC NEVUS-is defined as a mole present at birth and measuring more then 20cm diameter.  Up to five per-cent (5%) of these giant birthmarks may develop into melanomas. 

AMELANOTIC MALIGNANT MELANOMA- Is without melanin pigment.  Not having the “darkness” of “typical” melanoma they can be very difficult to recognize.  They show up as pink or red growths.

ACRAL LENTIGINOUS MELANOMA- is not attributed to sun exposure.  This is the type of melanoma that killed Reggae singer, Bob Marley.

Unusual Melanoma Variants

MUCOSAL MALIGNANT MELANOMA-(less then 5 per-cent (5%) of all melanomas) which may occur in the nasal or oral cavities (1.9%), genitals, including vagina (0.7%), anus and rectum (0.3%), urethra (0.2%), oesophagus (0.1%).   These melanomas may have an initial radial lentiginous growth, but there is also a more aggressive nodular type that only grows vertically.  Diagnosis is very difficult due to the hidden locations, and often the lesions simulate anal hemorrhoids, gingival vascular formations or chronic sinusitis.

OCULAR MALIGNANT MELANOMA-Up to 5% of all melanomas originates from the eye.

Since the unusual variants of melanoma are so rare, it is not known if they respond in the same way to treatment as the more common cutaneous melanomas.  In addition, the diagnosis is often very difficult due to their hidden locations.