Amelanotic Melanoma (AM)
Amelanotic literally means “without melanin.” This could be classified as more of a general subcategory than a specific type, but since it is often ignored until too late (due to the lack of dark coloration) it is being included here under Types.
Amelanotic melanoma appears as a lesion that has little or no color (non-pigmented) or may appear red, pink or scarlike-white. It has an asymmetrical shape, and an irregular faintly pigmented border.
Any of the types of melanoma may be amelanotic, but a particular amelanotic variety is called desmoplastic melanoma (DM). DM is most commonly found in acral lentiginous melanomas located subungually (under the nailbed), in lentigo maligna lesions or after cryotherapy for treatment of lentigo maligna. Desmoplastic is a unique melanoma in that the overall survival of patients with thick (>4mm) tumors appears to be longer than that of the other melanoma types (Zettersten et al, 2002). It appears on the head and neck, up to 40% recur locally, and most often metastasizes to the lung while sparing the regional lymph nodes (Jaroszewski et al, 2001). Recurrence rates are high because the tumor cells have a spindle shape making them vulnerable to inadequate surgical excision (Liu et al, 2003).
Any lesion that is scar-like in appearance or grows next to a previously treated melanoma should be examined immediately.
According to one study, there is a 13-month average delay in diagnosis due to the lack of pigmentation and treatments for previous misdiagnoses, so they are often advanced when found.