Most severe type of malignant melanoma mostly arises from:

Ans: (b) Arising de novoRook's Dermatology and Essentials in DermatologyMost severe type is Nodular melanoma. It often arises de novo and carries the worst prognosis. MALIGNANT MELANOMA - SUBTYPESSuperficial spreading melanoma is by far the most frequent type of melanoma.Most common sites: In female - leg and the In males - back.If the melanoma is developing in a pre-existing naevus, which occurs in approximately 50% of lesions, the irregular appearance of the growing melanoma may contrast strikingly with the more regularly pigmented and outlined residual naevus component.All patients with suspected malignant melanoma should have an excision biopsy of the lesion carried out with a margin of 1-2 mm of clinically normal skin.Incisional or punch biopsies should NOT be performed in suspected melanoma because of sampling error, because an inaccurate tumour thickness may be obtained due to biopsy trauma, and also because the overall shape and symmetry of the whole lesion is important to the diagnosis of melanocytic lesions. There is a theoretical risk of displacing melanoma cells deeper into the dermis.The essential pathological features of superficial spreading melanoma are the presence of a focus of malignant melanoma cells invading the dermis with areas of in situ malignant change in the adjacent epidermis.MELANOCYTE DIFFERENTIATION MARKERSS100gp100/HMB-45TyrosinaseMART-1/Me!an-AHMW_MAAS100 is less specific than the other three, but highly sensitive and therefore is usually used in combination with at least one of the others.Invasive melanomas up to 2 mm thick may be safely treated with a minimal excision margin of 1 cm.In patients with thicker tumours, the recommended excision margin is 2 to 3 cm.TYPES OF MELANOMAA. Superficial spreading melanomaMost common subtypeAccounts for 70% casesPresents as flat or slightly elevated brown lesionVariegate pigmentation (Black, blue or pink discolouration)Prognosis is worse than lentigo maligna melanoma typeB. Nodular melanomaPresents as a dark brown to black papule or dome shaped noduleUlcerates and bleeds with minor traumaRapid growth over weeks to monthsCarries Worst Prognosis*C. Lentigo maligna melanoma (Hutchinson's freckle)Slowly grows over 5-20 yearsArises in only a small percentage of the intra-epithelial precursor lesion, the lentigo malignaMalignant Melanoma in situGood prognosisD. Acral lentiginous melanomaLeast common subtypeOccurs on the palms, soles, beneath the nail plate (Subungual variant)Pigment spread to the proximal or lateral nailfolds (Hutchinson sign) - Hallmark of this subtypePrognosis is worse than superficial spreading melanoma subtypeE. Amelanotic melanomaNonpigmentedPink or flesh coloredMimics basal cell carcinoma or Squamous cell carcinomaMost commonly occurs in the setting of melanoma metastasis to the skinInability of the poorly differentiated cancer cells to synthesize melanin pigment