These changes are evenly distributed throughout the lesion. Malignant change in cellular blue nevi may be heralded by a sudden increase in size and occasionally ulceration. Cases of eruptive blue nevi have been reported, some following skin trauma such as sunburn. Common blue nevi tend to be smaller than 1 cm and cellular blue nevi tend to be larger than 1 cm. In general, imaging studies are not necessary.
Some authors advocate the use of dermoscopy in the evaluation of atypical pigmented lesions.
The clinical utility of this method is currently controversial. A histologic continuum exists from common blue nevi to cellular blue nevi. Scattered melanophages are usually noted. There are no mitoses. Occasional mitoses may be seen but significant cytologic atypia and areas of necrosis are absent.