Superficial spreading melanoma (SSM) was the most common subtype in NHW, HW, and API, whereas in Blacks, it was the second most common subtype.
(3-8,16) Historically, three main subtypes of melanoma including superficial spreading melanoma (SSM), lentigo maligna melanoma (LMM) and nodular melanoma (NM) were first described in 1969; (9) desmoplastic melanoma (DM) was added in 1971; (12) and acral lentiginous melanoma (ALM) was introduced in 197710 and defined in 1980.
Recently, epidemiologic analysis led to the proposal of an "early-onset melanoma" category, which is predominantly associated with female sex, superficial spreading melanoma, and a lower extremity location, and a "late-onset melanoma" category, which is predominantly associated with male sex, lentigo maligna melanoma, and a head and neck location.
The histologic profile of superficial spreading melanoma consists of an asymmetric proliferation of uniformly atypical melanocytes that are found at all levels of the epidermis, with single or small aggregates of atypical melanocytes present in the stratum corneum or granulosum ("pagetoid growth").
In some cases, diagnostic considerations included dysplastic nevus and
superficial spreading melanoma. In 2 cases, FISH was performed to confirm a suspected but histologically challenging diagnosis of nonsarcomatoid desmoplastic melanoma.
The unique clinical and histologic features discussed above and summarized in Table 2 suggest that lentiginous melanoma represents a distinct clinicopathologic entity from a common lentiginous nevus, dysplastic nevus,
superficial spreading melanoma, and lentigo maligna.
Vertical growth pattern in
superficial spreading melanoma is defined as the presence of 1 or more dermal clusters larger than the largest epidermal cluster and/or the presence of any mitotic activity in the dermis.
In the case of
superficial spreading melanoma, the patches or plaques can measure up to 2.5 cm.
Nodular melanomas (NMs) constitute the second commonest clinical subtype of melanomas (representing 14%-30% of the cases of melanomas), following the more common
superficial spreading melanomas. The less common subtypes are lentigo maligna melanomas and acral lentiginous melanomas.
(4,5,20,21) Nodular and
superficial spreading melanomas occur less commonly in the black population, and lentigo maligna melanoma is rare.
Melanomas in children arise from congenital nevi, de novo nodular nevi, and
superficial spreading melanomas that are sun induced, said Dr.
Pan-nuclear staining is also observed in a subset of neoplastic cells in
superficial spreading melanomas and nodular melanomas, but not to the extent seen in the setting of lentiginous melanomas.