The labial melanotic macule is a distinct entity that appears in adults as a well-defined brown or black pigmented macule on the lip. Patients followed up for up to 13 years had no adverse developments, a finding indicative of the benign nature of this lesion. The halo lesion typically involutes during a period of months in the absence of clinical signs of inflammation. Histologically, a chronic lymphocytic infiltrate surrounds the nevus cells, which may represent an autoimmune phenomenon. Although benign, spindle cell nevus may closely resemble a malignant melanoma.
Excisional biopsy is therefore advisable in many cases.
The mongolian spot is a bluish macule that is seen in newborns of dark-skinned races. The lesion usually disappears by 3 or 4 years of age. This malformation consists of a group of melanocytes with long, thin surface projections in the middle and lower thirds of the dermis and in subcutaneous fat. No tendency toward malignant transformation exists. The cellular blue nevus, which appears as a blue-black nodule or an indurated plaque, contains two types of cells, spindle shaped and rounded.