Skin, Combined nevus

The common or classic blue nevus is a small slate-blue to black-blue macule or papule found most commonly on the extremities. It is composed of elongated, sometimes finely branching, melanocytes in the interstices of the dermal collagen of the mid and upper dermis. There are some admixed melanophages. Some lesions show dermal fibrosis (sclerosing blue nevus). In about 3% of cases, there is minimal pigment present. Such cases have been called ‘amelanotic’ or ‘hypopigmented’ blue nevi. Occasionally, an overlying intradermal nevus is present: such lesions are called combined or ‘true and blue’ nevi. Combined nevi are characterized by the presence of two or more different types of melanocytic nevi in a single lesion. ‘True and blue’ nevi are the most common type of combined nevus.

This case exhibits a well-circumscribed intradermal melanocytic lesion (9mm) with a combined appearance. It shows superficial epithelial nevoid cells with mild mineralization and focal nesting consistent with an ordinary intradermal nevus and a deeper scattered banal spindle/oval cell proliferation with prominent admixed melanophages consistent with a common blue nevus. The lesion is symmetrical with nevoid architecture. There is no cytologic atypia or mitotic activity within lesional cells.