Melanocytic Acral Nevus With Intraepidermal Ascent of Cells: Five Cases

To the Editor: Acral melanocytic nevi are found in 4%–9% of the general population.1 These lesions exhibit various clinical, dermoscopic, and microscopic characteristics, making them unique and deserving of greater attention. Dermoscopy patterns include parallel furrows reticular, fibrillar, and atypical, with the first being the most common.1,2 Histologic analysis reveals melanocytes with mildly enlarged nuclei, variations in nuclear volume and architectural asymmetry,3 unlike nevi in other locations. Given these characteristics, such lesions can easily be mistaken for malignant or atypical to unfamiliar eyes, leading to unnecessary diagnoses and interventions. The observation of the ascent of melanocytes to the upper layers of the epidermis, in the absence of other histologic signs of malignancy, should be interpreted critically. This phenomenon can occur punctually in benign melanocytic lesions and represents a potential diagnostic pitfall because it is one of the diagnostic criteria for melanoma.4 Awareness of this finding is essential to avoid histologic misdiagnosis. This aim of this article was to report 5 cases of melanocytic acral nevus with intraepidermal ascent of cells, also known by the acronym MANIAC, coined by Leboit.5 Acral nevi have such distinctive characteristics that they are addressed in a separate chapter in the World Health Organization classification. The new edition of this publication mentioned MANIAC for the first time, consolidating it as a diagnostic entity in the context of acrally located nevi.6 Five distinct cases were analyzed, of which 4 (80%) were male patients. All lesions were excised because they presented at least one atypical feature (clinically or dermoscopically).7 The average age was approximately 9 years (maximum 14 years and minimum 3 years). Four lesions analyzed affected the lower extremities (2 on the feet and 2 on the legs) and one on the palm. All lesions had macroscopic dimensions—after fixation in 10% buffered formaldehyde—ranging from 0.6 to 0.2 cm, with an average of 0.4 cm (Table 1). All cases were junctional with a lentiginous distribution pattern. Isolated nests were identified in only 2 lesions. The cases presented melanocytes with mild atypia (the nuclei size did not exceed 1.5–2 times the size of the nucleus of the adjacent keratinocyte according to the WHO criteria). No mitoses were identified (Figures 1– 4). A chronic dermal inflammatory infiltrate was identified in 2 cases, and in one case, frequent melanophages were observed. TABLE 1. - Clinical Characteristics of the Presented Cases Case 1 Case 2 Case 3 Case 4 Case 5 Sex Male Male Male Female Male Age (yr) 7 13 3 14 9 Location Leg Hand Leg Foot Foot Dimension (cm) 0.4 0.3 0.2 0.5 0.6 The cases confirmed the previously described profile for MANIACs from a clinical and microscopic perspective.5 They are small lesions that occur in young patients and exhibit a clinically suspicious appearance. Contrary to the criteria for melanoma diagnosis,6 these lesions can have numerous ascending melanocytes, even at the lesion's periphery, that is, in the epidermis that extends beyond the intradermal component when it is present. Therefore, MANIAC is a benign melanocytic neoplasm that may exhibit some histologic features similar to melanoma. The young age of patients, small lesion size, absence of cytological atypia, and a lentiginous pattern with the spread of isolated cells are findings that assist in the microscopic diagnosis of these cases, avoiding unnecessary additional procedures.FIGURE 1.: Case 5 (A) dermoscopy image showing a predominant pigmented ridge pattern, (B) in detail.FIGURE 2.: Case 2 microscopic photograph showing a lesion with a purely lentiginous appearance with numerous melanocytes in the upper layers of the epidermis. A, ×40 H&E, (B) ×100 H&E, (C) ×200 H&E.FIGURE 3.: Case 3 microscopic photographs: (A) Panoramic view demonstrating a small lesion H&E ×40, (B) note the presence of inflammatory infiltrate and melanophages in the dermis H&E ×100, (C) note that the lesion is predominantly lentiginous but presents nests H&E ×200, and (D) in detail, cellular atypia with nuclei size not exceeding 1.5–2X the size of the adjacent keratinocyte H&E ×400.FIGURE 4.: Case 5 microscopic photographs: (A) Panoramic view demonstrating the predominant lentiginous pattern of the lesion H&E ×40, (B) note the presence of small nests among lentiginous melanocytes ×100 H&E, and (C and D) demonstrating melanocytes ascending through the spinous layer. Note that there is no nuclear atypia H&E ×40.