Dermatology: Practical and Conceptual Observation | Dermatol Pract Concept 2017;7(3):7 35 DERMATOLOGY PRACTICAL & CONCEPTUAL www.derm101.com Case Report A 65-year-old male presented with a pigmented lesion on his left hip, that he had noticed for some months. On examination a 10 x 15-mm asymmetrically shaped dark brown macule was seen (Figure 1). Dermatoscopically the lesion show asymme- try of patterns and colours. Variegated light and dark brown reticular lines are seen in the periphery and white reticular lines in the centre. A structureless white area was extending to the periphery. An asymmetrical lesion with pigmented reticular lines in the periphery and white reticular lines in the centre, together with an eccentric white structureless zone strongly favours a diagnosis of melanoma with regression and dermal fibrosis. Another clue to melanoma is the occurrence of gray structures (Figure 2) [3]. The lesion was both clinically and der- matoscopically highly suggestive of melanoma and a diagnostic excision was performed. The histological sections showed broad and superficial zone of acanthosis with a reticulated pattern and clusters of mature sebocytes attached to the bases of the anastomosing rete ridges. Focal coalescence of sebaceous lobules and papillary dermis fibrosis are also seen (Figure 3). Based on this constellation of findings the diagnosis of RASD was rendered. Immunohistochemistry revealed intact DNA mismatch repair proteins (MLH1, MSH2, MSH6, and PMS2). Reticulated acanthoma with sebaceous differentiation mimicking melanoma Felipe Ribeiro1, Elizabeth Leocadia1, Ricardo S. Macarenco2, Jan Lapins3, Pascale Huet4, Bengu Nisa Akay5, Denise Steiner1 1 Department of Dermatology, Mogi das Cruzes University, Mogi das Cruzes, Brazil 2 Department of Pathology, Hospital Israelita Albert Einstein, São Paulo, Brazil 3 Department of Dermatology, Karolinska University Hospital, Stockholm, Sweden 4 Dermatology, Montferrier-sur-lez, France 5 Department of Dermatology, Ankara University, Ankara, Turkey Key words: reticulated acanthoma with sebaceous differentiation, RASD, melanoma, mimicker, dermatoscopy, dermoscopy, histopathology Citation: Ribeiro F, Leocadia E, Macarenco RS, Lapins J, Huet P, Akay BN, Steiner D. Reticulated acanthoma with sebaceous differentiation mimicking melanoma. Dermatol Pract Concept 2017;7(3):7. DOI: https://doi.org/10.5826/dpc.0703a07 Received: January 11, 2017; Accepted: May 27, 2017; Published: July 31, 2017 Copyright: ©2017 Ribeiro 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: Felipe Ribeiro, MD, Department of Dermatology, Mogi das Cruzes University, 201 Ottavio Giannotti Street, 71 08773510 Mogi das Cruzes, São Paulo, Brazil. Tel. + 55 11 981971166 Email: rsfeliperibeiro@gmail.com Reticulated acanthoma with sebaceous differentiation (RASD) is a rare, benign cutaneous tumor with peculiar histopathologic characteristics [1]. RASD had been described under various synonyms such as superficial epithelioma with sebaceous differentiation, sebocrine adenoma, poroma with sebaceous differentiation, and seborrheic keratosis with sebaceous differentiation [2]. Clinical differential diag- nosis of RASD includes cutaneous superficial epithelial neoplasia such as Bowen’s disease, superficial basal cell carcinoma (BCC) and intraepidermal eccrine poroma [1]. We report the first case of RASD mimicking both clinically and dermoscopically a melanoma. ABSTRACT mailto:rsfeliperibeiro@gmail.com 36 Observation | Dermatol Pract Concept 2017;7(3):7 to our case, most significantly the occur- rence of yellow structures, implicating sebaceous differentiation, something that Discussion To our knowledge, this is the first case of RASD mimicking melanoma. There is only one previous report on derma- toscopic features of RASD, that shows some important differences compared Figure 1. A 10 x 15 mm asymmetric brown macule on the hip of a 65-year-old male. [Copyright: ©2017 Ribeiro et al.] were not present in our case [1]. RASD may be rare; however, another possibil- ity is that RASD has been misinterpreted as seborrheic keratosis, and not excised or not regarded as worth reporting [4]. The histology of the present case has all the features characteristic of RASD. Muir-Torre syndrome (MTS) is char- acterized by the presence of cutaneous sebaceous neoplasia, such as sebaceous adenoma, sebaceous carcinoma, and sebaceoma. Patients with MTS develop carcinoma of internal organs very fre- quently, mostly in the gastrointestinal system, and occasionally in the genito- urinary system, and a single skin tumor with sebaceous differentiation can be a sign of MTS [5,6]. Immunohistochemis- try has emerged as a practical screening tool for MTS. Mismatch repair proteins MLH1, MSH2, MSH6, and PMS2 are currently tested for this purpose [7]. Most sebaceous neoplasms in MTS lack expression of at least one of the above- Figure 3. Dermatoscopic findings in an RASD mimicking melanoma. Pigmented reticular lines in the periphery. White reticular lines in the center extending into an eccentric white structureless zone. Gray structures. No yellow structures indicating sebaceous differentiation can be seen. [Copyright: ©2017 Ribeiro et al.] Figure 2. Dermatoscopic findings in an RASD mimicking melanoma. Pigmented re- ticular lines in the periphery. White reticular lines in the center extending into an eccentric white structureless zone. Gray structures. No yellow structures indicating sebaceous differentiation can be seen. [Copyright: ©2017 Ribeiro et al.] Observation | Dermatol Pract Concept 2017;7(3):7 37 5. Shon W, Wolz MM, Newman CC, Bridges AG. Reticulated acanthoma with seba- ceous differentiation: another sebaceous neoplasm associated with Muir-Torre syn- drome? Australas J Dermatol. 2014;55 (4):e71-73. 6. Rothenberg J, Lambert WC, Vail JT Jr, Nemlick AS, Schwartz RA. The Muir- Torre (Torre’s) syndrome: the significance of a solitary sebaceous tumor. J Am Acad Dermatol. 1990;23:638–640. 7. Jessup CJ, Redston M, Tilton E, Reimann JD. Importance of universal mismatch repair protein immunohistochemistry in patients with sebaceous neoplasia as an initial screening tool for Muir-Torre syn- drome. Hum Pathol. 2016;49:1-9. 8. Roberts ME, Riegert-Johnson DL, Thomas BC, et al. A clinical scoring system to identi- fy patients with sebaceous neoplasms at risk for the Muir-Torre variant of Lynch syn- drome. Genet Med. 2014;16(9):711-716. icking melanoma both clinically and dermoscopically. References 1. Ito T, Yoshida Y, Furue M, Yamamoto O. Dermoscopic features of reticulated acanthoma (superficial epithelioma) with sebaceous differentiation. Eur J Derma- tol. 2012;22(5):704-706. 2. Haake DL, Minni JP, Nowak M, Abenoza P, Nousari CH. Reticulated acanthoma with sebaceous differentiation. Lack of as- sociation with Muir-Torre syndrome. Am J Dermatopathol. 2009;31(4):391-392. 3. Kittler H, Rosendahl C, Cameron A, Ts- chandl P. Dermatoscopy. An Algorithmic Method Based on Pattern Analysis. Vien- na: Facultas Verlags, 2011. 4. Fukai K, Sowa J, Ishii M. Reticulated acan- thoma with sebaceous differentiation. Am J Dermatopathol. 2006;28:158. mentioned proteins, while sporadic seba- ceous neoplasms are expected to present all four proteins intact (positive) in the neoplastic cells’ nuclei. Although the present case was clinically unlikely to be associated with MTS [8], a case of RASD has been recently documented in association with MTS [5]. Thus, immunohistochemistry was performed in order to rule out such association, and it revealed intact (positive) nuclear proteins, yielding a negative screening result for MTS. This immunoprofile is in agreement with most previous reports on RASD that studied mismatch repair proteins by immunohistochemistry. In conclusion, we have presented the dermatoscopic findings in an unusual case of RASD and to our knowledge, we describe the first case of RASD mim- https://www.ncbi.nlm.nih.gov/pubmed/?term=Ito%20T%5BAuthor%5D&cauthor=true&cauthor_uid=22858895 https://www.ncbi.nlm.nih.gov/pubmed/?term=Yoshida%20Y%5BAuthor%5D&cauthor=true&cauthor_uid=22858895 https://www.ncbi.nlm.nih.gov/pubmed/?term=Furue%20M%5BAuthor%5D&cauthor=true&cauthor_uid=22858895 https://www.ncbi.nlm.nih.gov/pubmed/?term=Yamamoto%20O%5BAuthor%5D&cauthor=true&cauthor_uid=22858895 https://www.ncbi.nlm.nih.gov/pubmed/?term=Yamamoto%20O%5BAuthor%5D&cauthor=true&cauthor_uid=22858895 https://www.ncbi.nlm.nih.gov/pubmed/22858895 https://www.ncbi.nlm.nih.gov/pubmed/22858895