Pigmented epidermotropic breast cancer metastases: A rare variant with a particularly unusual feature.

Pigmented epidermotropic breast cancer metastases are a rarity, often clinically misdiagnosed as melanocytic lesions. Histopathologically, they show a dermal proliferation of neoplastic metastatic cells that extend to the overlying epidermis in a pattern identical to that seen in primary Paget disease (PD). Differential diagnosis should be established with entities with a similar presentation, such as pigmented mammary PD and malignant melanoma. Immunohistochemistry may be useful for this purpose. We present a new case of pigmented epidermotropic breast cancer metastases with a particularly unusual feature: the absence of dermal infiltration by neoplastic cells, thus considered as pure epidermotropic metastatic involvement. [ABSTRACT FROM AUTHOR]