A lesson learnt: retrospection in a case of pilomatricoma mimicking as parotid neoplasm

DOI: 10.1590/S1679-45082015AI3096 A 10-year-old girl presented with a painless, slow-growing swelling on left pre-auricular region that was noticed for 2 years (Figure 1). The swelling was bosselated, nontender, firm-to-hard on palpation, had poorly-defined margin, and measured approximately 3.5cm x 3.0cm. In addition, it had restricted mobility, and seemed to be of parotid origin, with overlying skin apparently stretched and fixed. The ultrasonography was unable to delineate the depth and confirm the involvement of the parotid, although fine needle aspiration cytology (FNAC) suggested pleomorphic adenoma. For this reason, we decided to perform superficial parotidectomy. The Figure 1. The pre-operative image shows a diffuse swelling in the left preauricular region producing an impression of a parotid mass. Note the “tent sign” (arrow). The skin appears taut and stretched. On careful examination, a faint bluish tinge over the lesion could be seen Figure 2. Histopathology shows two predominant cell population of pilomatricoma – the basophilic basaloid cells with scanty cytoplasm, prominent nuclei and indistinct borders, and the eosinophilic anucleated “ghost cells” with relatively distinct borders, and with a transitional zone in between. As the tumor ages, the basaloid cells undergo apoptosis and become “ghost cells”. Hematoxylin-eosin x 400