Scattered clear cells along the basal layer of the epidermis

Lack of melanin, nesting, cytological atypia

AE1/AE3 cytokeratin (+), mCEA (+), EMA (+), GCDFP-15 (+)

S100 (−), HMB 45 (−), Mart 1/Melan A (−)

Scattered bland cells with pyknotic nuclei, perinuclear halo and pale cytoplasm in the upper layers of the epidermis

Absence of atypia, nesting

HMWCK (+)

mCEA (−), HMB 45 (−), S-100 (−), Mart 1/Melan A (−)

Bland cells with round nuclei and clear pale cytoplasm that predominate in the basal layer of the epidermis

Absence of pleomorphism and cytological atypia

EMA (+), LMWCK (+), CK 7 (+)

HMWCK (−), mCEA (−), HMB 45 (−), Mart 1/Melan A (−)

Plump, spindle and epithelioid cells with abundant eosinophilic cytoplasm and inconspicuous bland nuclei

Cells mainly in the superficial dermis with varying degree of epidermal extension

S-100 (+), calretinin (+), inhibin (+), CD68 (+)

Mart 1/Melan A (−), HMB 45 (−)

Well defined nests of large cells with distinct intercellular bridges or basaloid cells with small dark staining nuclei

Large, dendritic melanocytes scattered through the epidermis in the melanoacanthoma variant

Columns and sheets of basaloid to squamoid cells with intervening horn cysts and slender elongated rete ridges

Absence of cytological atypia

HMWCK (+) (fig 4B), P63 (+) (fig 4C)

S-100 (−) (fig 4D), HMB 45 (−), Mart 1/Melan A (−)