Agminated Acquired Melanocytic Nevi of the Common and Dysplastic Type

Abstract

Dear Editor: 'Agminated' refers to circumscribed grouping of lesions confined to a localized area of the body. Pigmented lesions that have been described as agminated includes melanocytic nevi1, Spitz nevi2, nevi spilus3, blue nevi4, and multiple lentigines5. However, the presence of acquired common and dysplastic nevi (ACDN) arranged in an agminated pattern has not been well-established. Herein, we describe a patient with multiple agminated acquired melanocytic nevi, several of that were histologically characterized as dysplastic nevi. A 16-years-old female presented with multiple irregular moles on her right inguinal area (Fig. 1A). Her parents reported that this cluster of nevi developed at the age of 6 years, and continuously increased in numbers and sizes. No family history of melanoma or multiple moles was present. Physical examinations revealed more than 40 melanocytic nevi clustered in a 5×5 cm skin area on her right inguinal area, where several of these nevi were irregular with variegation of color and a diameter greater than 5 mm (Fig. 1A). No background pigmentation within or surrounding the cluster was noted clinically or even with Wood's light examination. Dermoscopy of the clustered nevi revealed a diffuse patchy reticulation (Fig. 1B). A biopsy from a clinically atypical nevus demonstrated a lentiginous, compound-melanocytic nevus with architectural disorder in the epidermis. In the dermoepidermal junction, the nests of nevus cells were profused in the tips and sides of elongated rete ridges. In the center of the nevus, nests of melanocytes are present in the papillary dermis (Fig. 2A). There were scattered single cells in a lentiginous array without continuous proliferations (Fig. 2A). A few atypical melanocytes with large, irregularly shaped, hyperchromatic nuclei lay individually or within a small group (Fig. 2B). The diagnosis of dysplastic nevi was confirmed by the presence of an architectural disorders and cytologic atypia. Several nevi within the cluster had clinical, dermoscopic, and histologic features which are commonly attributed to dysplastic nevi. Dysplastic nevi have been the subject of ongoing controversy regarding its definition and use of more than 20 years6. It is argued that dysplastic nevi are both acquired and common, and they should be regarded as nothing but common nevi. However, when considering a review article from Elder6, theses lesions have been only significant in relation to melanoma, as stimulants of melanoma, as markers of risks for melanoma, and as potential and occasional actual precursors of melanoma. Therefore, clinical and histological classifications of nevi have the most important purpose of categorizing these lesions so that dysplastic nevi can be distinguished, clinically and histologically, from melanoma. In our patient, the diagnosis of dysplastic nevi was based on the clinical, dermoscopic and histologic features. Agminated dysplastic lesions, similar to our case should be distinguished from other forms of dysplastic nevi, which show a segmental distribution without a definite clustering. Two cases of dysplastic nevi with segmental distributions have been previously reported in the literature7,8. Both of the cases are not being described as agminated, because multiple dysplastic nevi were distributed throughout the patients' upper left quadrant. One thing that deserves the attention of clinicians is that malignant melanoma developed within the lesions of both cases. There still exists much controversy about the presence of agminated ACDN. Marghoob et al.9 and Bragg et al.10 previously reported 5 cases of agminated ACDN. Unlike our case, however, agminated lesions were superimposed on an underlying dysplastic nevus syndrome phenotype in 4 out of 5 cases. In the 2 cases of the 5 reported as agminated ACDN, malignant melanoma did not developed within the agminated lesion, but within the underlying dysplastic nevus syndrome phenotype. The authors believed that agminated ACDN were a new, previously not described, clinical variant of dysplastic nevi. In conclusion, the uncertainty in the biological behaviors of agminated ACDN suggests a strict follow-up for this unusual entity.