CPD • Clinicopathological case CED Clinical and Experimental Dermatology An asymptomatic nodule on the forearm I. Oguz Topal, 1 Y. Topal, 2 D. Sakiz 3 and S. G€ ung € or 1 1 Department of Dermatology, Okmeydani Research and Training Hospital – Dermatology, Istanbul, Turkey; 2 Department of General Surgery, Taksim Research and Training Hospital, Istanbul, Turkey; and 3 Department of Pathology, Bakirkoy Dr Sadi Konuk Research and Training Hospital, Istanbul, Turkey doi: 10.1111/ced.12376 Clinical findings A 53-year-old woman presented with a solitary lesion on her left forearm, which had first appeared approxi- mately 20 years earlier and had gradually increased in size. Physical examination (Fig. 1) revealed a firm, reddish-brown, dome-shaped nodule, 30 9 20 mm in diameter. In addition, there were yellow-brown, circu- lar crusts of around 1 mm in size over the lesion, along with a bleeding ulcerative area. Histopathological findings On histological examination of a skin biopsy specimen, hyperkeratosis, light acanthosis and focal basaloid cell proliferation were seen in the epidermis. In the dermis, there were cystic dilated and branching tubular struc- tures with papillary projections into the lumen, sur- rounded by a fibrous stroma. These ducts were surrounded by two layers of epithelial cells. The ductal cells were primarily cuboidal, but some were columnar and/or flattened. The cuboidal cells of the inner layer of the tubular structures showed decapitation secretion (Fig. 2a,b) and were positive for epithelial membrane antigen (EMA) and gross cystic disease fluid protein (GCDFP)-15 (Fig. 2c,d). What is your diagnosis? Correspondence: Dr Ilteris Oguz Topal, Department of Dermatology, Batman State Hospital, Batman 72070, Turkey E-mail: drilteris@yahoo.com Conflict of interest: the authors declare that they have no conflicts of interest. Accepted for publication 1 February 2014 Figure 1 A reddish-brown, dome-shaped, nontender nodule, 30 9 20 mm in size, on the patient’s forearm. ª 2014 British Association of Dermatologists 760 Clinical and Experimental Dermatology (2014) 39, pp760–762