Malignant melanoma in situ
— intraepidermal: spread can be lentiginous (continuous basal layer) or upward (single cells, nests, "buck-shot" or Pagetoid) in this noninvasive radial growth phase.
— face/Hutchinson's melanotic freckle: a lentiginous single and nested basal layer proliferation of melanocytes with cytological atypia (enlarged, hyperchromatic angular nuclei and cytoplasmic vacuola-tion) ± architectural atypia (expanded junctional nests) on a background of dermal solar elastosis. Expansion and spindling of junctional nests and any clinically nodular areas should raise a suspicion of invasion. The clinical term lentigo maligna encompasses any degree of proliferation that is confined to the epidermis (i.e. it includes Clark level I or melanoma in situ), while lentigo maligna melanoma implies the presence of dermal invasion (at least Clark level II).
Superficial spreading melanoma
— radial phase of spread.1
Usually an asymmetrical lateral border of atypical junctional cell nests with a central segment of epidermis showing upward melanocytic spread (single cells/nests/"buck-shot" patterns). Moderate dusty pigmentation ± a dermal component related to the growth phase.
— vertical phase of spread.2
Often exophytic/nodular and thick ± pigmentation, with <2 or 3 rete pegs showing atypical junctional nests at the lateral border of the lesion.
— sole of foot, nail bed, mucosae. Features are often a combination of lentigo maligna and superficial spreading patterns ± a nodular, vertical growth phase component.
1Radial growth phase includes melanoma in situ (i.e. intraepidermal) ± microinvasion of the papillary dermis. The radial phase may be indolent with no metastatic potential and 95-100% survival rate. The dermal component is usually <1 mm thick, i.e. the lesion is wider than it is deep and can have morphologically bland cell nests (usually <10 cells across) of uniform size and cytological appearance. This may be accompanied by signs of regression with a brisk lymphocytic response. The radial phase potentially progresses by clonal expansion to the vertical phase. 2Vertical growth phase tumour comprises expansive nests, nodules or plaques of cyto-logically atypical melanoma cells in the dermis; it implies a biological potential for metastatic spread and is the main determinant of prognosis. The cell nests are usually larger than the biggest intraepidermal nest, >10-25 cells in dimension, show variation throughout the lesion, mitoses and a variable host dermal lymphocytic response. Vertical growth phase melanomas are often at least Clark level III and thicker than 1 mm with an inconstant relationship between the width and depth of the lesion.
Breslow depth or thickness (mm) = the maximum vertical depth from the top of the granular layer or ulcerated surface to the deepest point of invasion
Figure 21.1. Malignant melanoma. |QAJ
In general, these main subtypes do not show prognostic differences but there is correlation with recurrence and metastases, e.g. nodular melanoma is often thick (with a significant Breslow depth) and ulcerated. Knowledge of the various clinicopathological subtypes also helps in their diagnostic recognition.
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Complete Guide to Preventing Skin Cancer. We all know enough to fear the name, just as we do the words tumor and malignant. But apart from that, most of us know very little at all about cancer, especially skin cancer in itself. If I were to ask you to tell me about skin cancer right now, what would you say? Apart from the fact that its a cancer on the skin, that is.