Pilomatricoma Arising at an Influenza Vaccination Site

775 Pilomatricoma is a benign skin neoplasm that arises from hair follicle matrix cells. It occurs on the head, neck, and upper extremities, and less frequently on the trunk and lower extremities. The etiology of pilomatricoma is subject to controversy. Trauma, insect bites, or surgery are thought to be antecedent events to the onset of the tumors. Influenza vaccination is a common annual event among individuals. Complications are usually mild and selflimiting. Prophylactic influenza vaccinations rarely cause cutaneous complications. Few cases of foreign body granuloma, infectious reaction, and other cutaneous complications have been reported. In this article, we describe a case of pilomatricoma arising at an influenza vaccination site. Although there has been a report of an association between pilomatricoma and bacille Calmette-Guerin (BCG) vaccination [1], an association with influenza vaccination has not been reported previously. The clinical manifestations and progress of the case are presented in this report. A 7-year-old girl received her routine influenza vaccination in the left upper arm. One month later, a sensation of warmth and redness developed on the vaccination site. Serous discharge was drained with a small amount of blood. Three months later, the patient was referred to the plastic surgery outpatient department, where she presented with a pinkish ulcerative nodule on her left upper arm at the site of administration of the influenza vaccine. At that time, the nodule was covered with a dressing, but it gradually became harder to the touch and larger in size. Seven months later, the nodule reached approximately 10 mm in diameter, and was fixed firmly to deep subcutaneous tissue (Fig. 1). Ultrasonographic examination revealed a heterogeneous echo texture, surrounding subcutaneous fat infiltration, and subtle vascularity (Fig. 2). Clinical differential diagnoses included foreign body granuloma, postvaccinal lymphadenitis, Pilomatricoma Arising at an Influenza Vaccination Site