Intraepidermal Dendritic Melanocytes in Spitzoid Neoplasms

Abstract

Melanocytes with prominent bipolar dendritic processes are a well-recognized component of some dermal melanocytic lesions, the so-called “dermal dendritic melanocytic proliferations,”1 the most frequent of them being “common” blue nevus. Moreover, “compound” blue (Kamino) nevus,2 lentigo labialis,3 pigmented actinic keratosis,4 and melanoma 5 are characterized by the presence of dendritic melanocytes within the epidermis. Massi and LeBoit 6 also stated that “early” Reed nevus and spitzoid melanoma on sun-damaged areas are composed of junctional nests of melanocytes with delicate intraepidermal dendritic processes. We examined the histologic specimens of 45 consecutively excised nevi belonging to the morphologic spectrum of pigmented spindle cell Spitz/Reed nevus (lumped together as previously assessed 7). Moreover, seven cases of spitzoid melanoma metastatic to the sentinel lymph node were retrieved and also examined. All the selected cases were from the Department of Dermatology of the Second University of Naples. No case of “atypical Spitz tumor” as defined earlier 8 was selected. Each case had undergone dermoscopic examination and documentation before the surgical procedure. The individuals with Spitz/Reed nevus were mainly females (male-to-female ratio = 0.7:1), with a mean age of 22 years (age range: 1 to 58 years); most lesions were located on the limbs (29 cases, 64.4%). On dermoscopy, the most common pattern was described as “starburst” pattern 7 (17 cases, 37.8%). Histopathologically, 19 out of these 45 nevi showed clearly visible single intraepidermal dendritic melanocytes outside the junctional nests. These dendritic processes were thin and regular, mainly oriented perpendicular to the skin surface (Fig. 1). No significant difference was found between the 2 groups of nevi with and without single dendritic cells in terms of sex and age of the patients and of location and dermoscopic features of the lesions.