Unusual variants of malignant melanoma

Oral Atypical Cellular Blue Nevus: An Infiltrative Melanocytic Proliferation

“…While rare to absent in CBN [2], mitotic activity is nearly always seen in MBN [10,11], though at a variable rate. While mitotic rates often overlap in ACBN and MBN [8,18,19,22], the presence of mitotic activity in atypical blue nevi is associated with unfavorable biologic behavior [21] and multiple groups have reported that atypical mitoses are a feature of malignancy [4,9,11,13,28]. Our case lacked atypical cytologic features as may occur in ACBN.…”

“…For a specific discussion on the histologic differential diagnosis with other lesions sharing some features of ACBN (e.g. epithelioid blue nevus, deep penetrating nevus) the reader is referred to several recent reviews [3,19,20,22].…”

“…Cutoffs for distinguishing ACBN from CBN varies from [1-2 cm [17,18] to [2-3 cm [22] to [5 cm [3]. As the size increases from [3 cm [23] to [6 cm [3], melanoma is reported to be more likely.…”

“…However, multiple reports in recent decades of tumors with features intermediate between CBN and MBN prompted the controversial [15] designation of ''atypical blue nevus'' or ''atypical cellular blue nevus'' (ACBN) [16,17]. While similar clinically and apparently biologically to CBN [17], discrete histologic criteria for ACBN are currently under debate even among expert dermatopathologists [18][19][20][21][22]. The most often cited histologic criteria include asymmetry, a deeply infiltrative and irregular border, mild cytologic atypia, and mitotic activity [2 mm 2 [17,18,23].…”

Desmoplastic Melanoma

“…These lesions are usually painless. [7,8] The diagnostic challenge for desmoplastic melanoma is frequently attributed to the observation that more than half of all desmoplastic melanomas are amelanotic, or not possessing pigmentation. Therefore, they are commonly mistaken for benign lesions, such as dermatofibromas or scars.…”