A previously healthy 16-year-old girl presented to our department with a red tumor on her right upper arm that enlarged over 6 months. The lesion initially started as a small cutaneous nodule without obvious triggers that gradually developed and enlarged to form a red-colored tumor with a hard nodule inside. There was no history of local trauma or insect bite. Her personal, past, and family histories were unremarkable.
On physical examination, there was a 6 × 6-cm protuberant, thick-walled, and well-defined red bullalike tumor on the right upper arm, which extended 1 to 3 cm from the epidermal surface (Figure, A). Inside the tumor, a nontender, firm-to-hard nodule was palpated. There was no regional lymphadenopathy, and results of the rest of the physical and systemic examinations were normal. Laboratory examinations of hematologic, biochemical, and urinalysis tests were normal. The tumor was excised completely under local anesthesia, and part of the tissue was sent for pathological examination.