LAUSR

AAFX: aneurysmal atypical fibroxanthoma AFX: atypical fibroxanthoma ERG: ETS-related gene RP: rainbow pattern INTRODUCTION Atypical fibroxanthoma (AFX) is an uncommon spindle cell tumor of fibrous tissue most often located on the sun-damaged skin on the head and neck of elderly patients. It has a locally aggressive behavior and a tendency to recur after surgery but a low metastatic potential. Clinically, AFX presents as a rapidly growing solitary nodule, which sometimes becomes ulcerated. Several subentities exist, including the aneurysmal atypical fibroxanthoma (AAFX), which is the subject of this report. Dermoscopy of AFX usually shows a nonspecific pattern including slight pigmentation, reddish and whitish areas, and/or a polymorphic vascular pattern (eg, linear, dotted, hairpin, and highly tortuous vessels) irregularly distributed over the surface of the lesion. This pattern can also be seen in other clinically similar tumors, such as squamous cell carcinoma, angiosarcoma, Merkel cell carcinoma, and amelanotic melanoma. The dermoscopic term rainbow pattern (RP) is used for highly vascularized lesions with areas showing various colors of the rainbow on polarized dermoscopy. Hemosiderotic and aneurysmal variants of fibrohistiocytic tumors such as dermatofibromas have been described as presenting with a RP. RP has previously been reported in a case of AFX, but to the best of our knowledge, no cases of AAFX showing the dermoscopic RP have been reported.