2018 Volume 128 Issue 12 Pages 2659-2663
An 8-year-old Japanese boy presented with a hemispherical, smooth, and flexible, 25×23 mm nodule at the back of his head after a concussion one year previously. Our initial diagnosis was a mesenchymal tumor, so it was surgically removed for excisional biopsy. A pathological examination revealed that spindle cell proliferated from the dermis to the subcutaneous tissues. The immunohistochemical examination was positive for α-SMA, D2-40, and Ki-67 and negative for CD34. Chromogenic in situ hybridization analysis for USP6 rearrangement revealed positive results. Therefore, the patient was diagnosed with nodular fasciitis. No recurrence was observed to date. Recently, it has been found that USP6 rearrangement such as MYH9-USP6 gene fusion are specific to nodular fasciitis, which is often misdiagnosed as sarcoma. Therefore, the diagnosis of nodular fasciitis is sometimes confusing. However, identifying USP6 rearrangement is useful in confirming the diagnosis of nodular fasciitis in cases of insufficient results from a pathological examination alone.