Unusual variant of blue nevus associated with dermatofibromas.

The blue nevus is a variant of a melanocytic nevus that presents as blue-gray to blue or black papules or nodules measuring up to 1 cm in diameter; it has a predilection for females and can be congenital or acquired. The classification of blue nevi is complex, with biological behavior being benign, borderline, or malignant. The case we present is one of a 40-year-old woman with multiple dermatofibromas that appeared and increased gradually in size during pregnancy. Physical examination revealed three spherical, brownish to red-purple nodules localized on the left leg, right shoulder and right laterocervical area. In addition, on her right forearm, there was a 0.3 cm nodule with a discreet non-pigmented, elevated area and a blue perilesional border that appeared in her childhood, affirmative after stinging herself with a pencil. The patient's family history was negative for significant lesions. The laboratory and imagistic findings were normal. Four skin biopsies were performed. The histopathological examination revealed an uncommon blue nevus with two different populations of pigmented cells: spindle shaped or dendritic melanocytes diffuse distributed in the middle dermis and closely aggregated deeply pigmented melanocytes in the reticular dermis. The other three lesions were diagnosed as dermatofibromas: bland spindle shaped cells in a fibrous stroma, some cells with a storiform arrangement. The overlying epidermis was hyperplastic with acanthosis and hyperpigmentation of the basal cell layer. No mitoses were seen.