Signature nevi: individuals with multiple melanocytic nevi commonly have similar clinical and histologic patterns

Individuals with multiple melanocytic nevi oftentimes have melanocytic nevi, usually two, with similar clinical and histopathologic patterns that may be typical or atypical. The melanocytic nevi are known in common parlance as signature nevi [1, 2]. In addition to being aware of these nevi, finding multiple unconventional melanocytic nevi with architectural pattern asymmetric and/or cellular pattern atypical helps to lend credence to the diagnosis of melanocytic nevus rather than melanoma. In order to evaluate the concept of the signature nevus we reviewed the histopathologic patterns of melanocytic nevi from patients having at least two nevi with similar histologic patterns.


Introduction
Individuals with multiple melanocytic nevi oftentimes have melanocytic nevi, usually two, with similar clinical and histopathologic patterns that may be typical or atypical. The melanocytic nevi are known in common parlance as signature nevi [1,2]. In addition to being aware of these nevi, finding multiple unconventional melanocytic nevi with architectural pattern asymmetric and/or cellular pattern atypical helps to lend credence to the diagnosis of melanocytic nevus rather than melanoma. In order to evaluate the concept of the signature nevus we reviewed the histopathologic patterns of melanocytic nevi from patients having at least two nevi with similar histologic patterns.

Materials and methods
Melanocytic nevi from patients with multiple melanocytic nevi having at least two with similar histologic pattern were retrieved retrospectively from the files of Dermatopathol-     pattern" (n=52) and "melanocytic nevus, junctional, epidermal/interface pattern" (n=26), while "melanocytic nevus, nodular" was one of the least (n=2).

Discussion
The article "Signature nevi" [1] by Suh and Bolognia empha- When one encounters a troublesome or atypical histologic pattern in one melanocytic nevus from an individual with many melanocytic nevi, e.g., architectural asymmetry and/or focal cellular atypia, it is common and expected to find other melanocytic nevi from that patient to have similar atypical histologic patterns.
Melanocytic nevi have been reported to have a variety of clinical phenotypic patterns [11], and a variety of histologic anatomic (Figure 1), architectural ( Figure 2) and cellular patterns (Figure 3) [3], not unlike that situation commonly found in apocrine neoplasia [4] and inflammatory skin diseases [5]. On occasion, an unusual melanocytic nevus will present with clinical and histologic changes that may be difficult to differentiate from a melanoma ( Figure 5) and (Figure 6). A quandary often occurs when there are histologic changes in pattern architectural such as asymmetry or pattern combined cellular such as focal cellular atypia [6]. These variations may be found and are expected in melanomas as well as in some unusual melanocytic nevi, such as signature nevi [7], nevi with the "ugly duckling" sign [8,9], acquired nevi [10], congenital nevi, Spitz's nevi [11,12], dysplastic nevi [13], traumatized nevi, or those found on a "special site" such as the genitalia, perineum, thigh, umbilicus, palm, sole, scalp and ear, etc. In addition, some atypical patterns of melanocytic nevi are classified by acronyms such as MIN [14], SAMPUS and MELTUMP [15], and eponyms such as Unna, Clark, Reed, Miescher, Zitelli, Mark, Seab and Ackerman [16,17], or too often with hazy descriptive monikers such as atypical nevus, dysplastic nevus with architectural disorder with moderate to severe cytologic atypia. The latter are often used to announce uncertainty and indecision by the pathologist as to whether the melanocytic proliferation is benign or malignant. Those bewildering and evocative names unfortunately all too often bode ill for the patient and may lead to unwarranted surgical procedures, e.g. sentinel lymph node biopsy and lymphadenectomy [18]. Regrettably, to date, there is no unanimity or litmus test to distinguish between those unusual and tricky clinical and histologic melanocytic nevi, or melanocytic proliferations from subtle melanomas. Sorry to say, we must alas rely upon questionable subjective clinical and histologic morphologic criteria to arrive at a definitive diagnosis, nevus or melanoma [19,20].
In summary, we agree that awareness and knowledge of the fact that an individual with multiple melanocytic nevi is prone to have several melanocytic nevi with similar and   sometimes unusual clinical patterns (signature nevi) as well as common and/or unconventional histologic patterns (anatomic, architectural and cellular). As a result, this concept of signature nevi supports unusual findings, clinical and histologic, to be customary and expected in melanocytic nevi for a particular individual with many melanocytic nevi. When a melanoma is in the differential diagnosis of a lesion pigmented, this valuable lesson may help to eliminate mistakes [21], avoid over diagnosing melanoma, and eliminate unnecessary surgery. Thus, in the end, one will be more prone to arrive at an accurate, precise and definitive diagnosis of melanocytic nevus.