Dermatology: Practical and Conceptual 56 Quiz | Dermatol Pract Concept 2018;8(1):13 DERMATOLOGY PRACTICAL & CONCEPTUAL www.derm101.com Whitish halo on a papular pigmented lesion Martina Lambertini1, Barbara Corti2, Carlotta Baraldi1, Maria Lucia Tardio2, Michelangelo La Placa1 1 Dermatology Division, University of Bologna, Bologna, Italy 2 Section of Pathology, S. Orsola-Malpighi University Hospital, Bologna, Italy Citation: Lambertini M, Corti B, Baraldi C, Tardio ML, La Placa M. Whitish halo on a papular pigmented lesion. Dermatol Pract Concept. 2018;8(1):56-58. DOI: https://doi.org/10.5826/dpc.0801a13 Received: February 20, 2017; Accepted: November 11, 2017; Published: January 31, 2018 Copyright: ©2018 Lambertini et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: None. Competing interests: The authors have no conflicts of interest to disclose. All authors have contributed significantly to this publication. Corresponding author: Dr. Michelangelo La Placa, Dermatology Division, Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Via Massarenti 1, 40138 Bologna, Italy. Tel. +39-051-2143880; Fax +39-051-347847. E-mail: michelangelo. laplaca@unibo.it A 49-year-old healthy Caucasian woman presented with a sudden change in a lesion on her abdomen. At the time of our consultation, we observed a pigmented papular lesion, 1.5 cm in diameter, surrounded by an incomplete whitish halo with two dark rounded blotches at its top (Figure 1a). The patient had a fair skin phototype and chronic photo- aging, characterized by atrophic skin, wrinkling, and diffuse solar elastosis, especially on the sun-exposed areas. Dermos- copy showed a brownish irregularly oval plaque with a few dotted vessels and regular globules. On top of the lesion, two heavily asymmetric and pigmented blotches were visible: on the left, it was bluish and on the right side reddish (Figure 1b). Histopathological examination revealed a compound, predominantly intradermal melanocytic nevus with congeni- tal features adjacent to a focal scar, suggestive of a previous trauma or surgical procedure (Figure 2a). Within the lesion, an expanding dermal nodule was detected, characterized by nests of epithelioid melanocytes. No nuclear cell atypia, pleomorphism, mitosis, or pagetoid spread into the epider- mis was observed (Figure 2b). The nodule was characterized by large melanocytes with minimal pleomorphism, without evidence of necrosis (Figure 2c). The periphery of the nodule showed maturation of the melanocytes blending with the surrounding nevus. Cells of the congenital nevus and cells of the dermal nod- ule were positive for S-100 protein and negative for HMB45. The Ki-67 proliferation index was low in the congenital nevus but moderately high in the nodule, while p-16 was negative in the nodule, but positive in the remainder of the nevus. BAP-1 immunohistochemistry revealed BAP-1 nuclear stain- ing (Figure 2d). What is your diagnosis? Figure 1. (a) Clinical presenta- tion. Papular pigmented lesion measuring 1.5 cm in diameter, surrounded by an incomplete whitish halo and areas of hy- perpigmentation on its top. (b) Dermoscopic images revealed a regular pigmented network with two hyperpigmented blotches on its top, one bluish and one reddish, surrounded by an asymmetric vitiligoid halo. [Copyright: ©2018 Lambertini et al.] A B Quiz | Dermatol Pract Concept 2018;8(1):13 57 tochemical analysis was also performed in order to evaluate the loss of BAP-1 expression [8-10]. In our case, Ki-67 was moderately high in the PN and negative in the remaining congenital nevus, while p-16 was negative in the nodule, but positive in the remainder of the nevus. The presence of melanocyte maturation with sym- metrical architecture and the presence of p-16 in the lower part surrounding the nodule did not support the criteria for malignant melanoma. BAP-1 immunohistochemistry revealed BAP-1 nuclear staining in the proliferative nodule, supporting the benign nature of the melanocytic proliferation [8-10]. Our case is remarkable because of the patient’s age and the unusual clinical and dermoscopic features, characterized by an incomplete whitish halo corresponding to the focal scar and the reddish blotch on its top corresponding to the proliferative nodule on the left. It is possible, however, that her lesion had started primarily as a nodule, and the sudden occurrence of the depigmentation prompted the patient to seek medical advice. In conclusion, PNs are typically found in childhood but may develop in much older individuals, and every rapid change on a CMN should always lead to surgical excision. Figure 2. Histological findings. (a) Junctional and dermal melanocytic congenital nevus with a dermal nodule (he- matoxylin-eosin, 4x). (b) Dermal nodule with nests of typical epithelioid cells. The periphery of the nodule showed gradual loss of cell density and blended with the surrounding nevus (hematoxylin-eosin 10x). (c) High power view. Large melanocytes with minimal pleomorphism and without necrosis (hematoxylin-eosin 40x). (d) BAP-1 immunos- taining. Strong and diffuse nuclear staining in the proliferative nodule. [Copyright: ©2018 Lambertini et al.] Answer Proliferative nodule in a small congenital melanocytic nevus Explanation Proliferative nodules (PNs) are rare melanocytic neoplasms arising in congenital melanocytic nevi (CMNs) that usually have a very good prognosis but can mimic malignancy in the rapid onset and clinical features [1]. Nevertheless, histological analysis can be difficult and every new proliferation arising on a CMN poses a challenge to determine the differential diagnosis from a malignant melanoma [2-6]. Except for one case in a 17-year-old girl, PN prolifera- tion has been described exclusively in newborns or during childhood [2-3]. Despite the worrisome clinical morphol- ogy, characterized by a nodular or papular consistency that slowly regresses, the majority of these neoplasms are benign, confirming the extreme rarity of melanoma in infancy [2-6]. Sometimes immunohistochemical analyses can be helpful, using the melanocytic markers S-100, HMB-45 or Melan A and other antibodies against Ki-67 and p-16 [7]. Immunohis- 58 Quiz | Dermatol Pract Concept 2018;8(1):13 6. Vergier B, Laharanne E, Prochazkova-Carlotti M, et al. Prolifera- tive nodules vs. melanoma arising in giant congenital melanocytic nevi during childhood. JAMA Dermatol. 2016;152(10):1147- 1151. 7. Herron MD, Vanderhooft SL, Smock K, Zhou H, Leachman SA, Coffin C. Proliferative nodules in congenital melanocytic nevi: a clinicopathologic and immunohistochemical analysis. Am J Surg Pathol. 2004;28(8):1017-1025. 8. Piris A, Mihm MC Jr, Hoang MP. BAP1 and BRAFV600E expres- sion in benign and malignant melanocytic proliferations. Hum Pathol. 2015;46(2):239-245. 9. Uguen A, Uguen M. About BRAF Mutations and p16 Expression in Melanomas Associated With Blue Nevi or Mimicking Cellular Blue Nevi. Am J Surg Pathol. 2016;40(6):857. 10. Busam KJ, Sung J, Wiesner T, von Deimling A, Jungbluth A. Combined BRAF(V600E)-positive melanocytic lesions with large epithelioid cells lacking BAP1 expression and conventional nevomelanocytes. Am J Surg Pathol. 2013 Feb;37(2):193-199. References 1. Bastian BC, Xiong J, Frieden IJ, et al. Genetic changes in neo- plasms arising in congenital melanocytic nevi: differences be- tween nodular proliferations and melanomas. Am J Pathol. 2002;161(4):1163-1169. 2. Lowes MA, Norris D, Whitfeld M. Benign melanocytic prolif- erative nodule within a congenital naevus. Austral J Dermatol. 2000;41(2):109-111. 3. Kiyohara T, Sawai T, Kumakiri M. Proliferative nodule in small congenital melanocytic naevus after childhood. Acta Derm Vene- reol. 2012;92(1):96-97. 4. Nguyen TLT, Theos A, Kelly DR, Busam K, Andea AA. Mi- totically active proliferative nodule arising in a giant congenital melanocytic nevus: a diagnostic pitfall. Am J Dermatopathol. 2013;35(1):e16-21. 5. Christou EM, Chen AC, Sugo E, Barbaric D, Wargon O. Prolifera- tive nodules of undifferentiated spindle cells arising in a large con- genital melanocytic nevus. 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