The dictionary defines dysplastic as an “abnormal growth or development of cells, tissue, bone, or organ.”

The dictionary defines nevus as “any congenital anomaly of the skin, including moles and various types of birthmarks,” or “any congenital growth or pigmented blemish on the skin; birthmark, or mole.”

In 1978, the first report on what was named dysplastic nevus DN was published in the archives of dermatology by Wallace Clark and colleagues. The neoplasm was defined as a unique type of melanocytic nevus that occurred in two families with melanoma and multiple such nevi. Because the histological and clinical findings in the nevi of these patients were different from banal nevi, it was called DN, implying with unusual, atypical (or dysplastic) features. Soon after, similar lesions, clinically and histologically, were reported outside the familial melanoma setting, and called sporadic dysplastic nevi. Even in this nonfamilial setting, dysplastic nevi were found to increase a person’s risk for melanoma independent of other melanoma risk factors.

Thus, the epidemic of the dysplastic nevus was born. Around 10 % of the pathology material the author reads on a daily basis is to rule out dysplastic or atypical nevus. The neoplasm has progressively penetrated the awareness of the general public, in some cases producing fear in affected individuals, their friends, and relatives. Many times, a patient is told she had pre-melanoma or even early melanoma when the pathology report says “dysplastic nevus.” So how is this nevus diagnosed? What are the defining characteristics of dysplastic nevus? Are they reliable? Are they valid? Are they clinical or histological?

Clinically, DN has features of the ABCD of melanoma, well known to dermatologists, but are generally stable (hence with very little or no E). Histologically, the dysplasia or atypia is recognized both in the architecture of the proliferation as well as cytology of the nevus cells.

Architecturally, the proliferation is asymmetric and the junctional component of a compound dysplastic nevus extends beyond the dermal component laterally, resulting in the macular and papular components of a lesion. Additionally, junctional nevus nests occupy the sides or shoulders of the rete in addition to the tips which occurs in a banal nevus. Unlike in a banal nevus, nevus cells are also likely to be present as single units among the basal layer, so-called lentiginous melanocytic hyperplasia. A nevus cell may be present in the spinous layer but prominent pagetoid spread is not seen and should raise suspicion for melanoma. In a DN, the papillary dermis also reveals some changes. These include fibrosis, dilated capillaries, melanophages, and lymphocytes, altogether contributing to the pinkish appearance of many dysplastic nevi, especially those that are not pigmented.

In addition to the above architectural features of the dysplastic nevus, there may be cytological or nuclear atypia as well. Unlike in melanoma, the nuclear atypia is random, that is, not uniform among all the proliferating junctional nevus cells. In other words, the atypia is sporadic, affecting scattered individual nevus cells among otherwise unremarkable ones. The degree of atypia has been arbitrarily divided into mild, moderate, and severe.