Abstract
A 6-year-old boy was admitted to our hospital because of a subcutaneous tumor in his right upper arm. The tumor rapidly became large within a 2-week period. Roentogenography showed homogenous mass density without calcification. At the time of ultrasonography, a heterogenous solid mass with an obliterated border between the tumor and the fascia was noted MRI T2 weighted images revealed that the tumor had invaded the fascia An excisional biopsy was carried out due to suspicion of malignancy. The tumor was excised with the involved fascia. Spindle cell sarcoma was histologically suspected at surgery, but no definite histological diagnosis was made until a second opinion suggested nodular fasciitis. The patient is doing well with no clinical signs of recurrence. Nodular fasciitis is a benign reactive proliferation of myofibroblasts, and usually occurs in the forearm of adults. It can be misdiagnosed as a malingnant soft tissue tumor because of clinically rapid growth and highly cellular pseudo-sarcomatous proliferations. At the time of diagnosis of soft tissue tumor in children, nodular fasciitis must also be considered as a possible differential diagnosis to avoid misdiagnosis and overtreatment of this rare tumor.
