Giant nodular fasciitis originating from the humeral periosteum: A case report

BACKGROUND: Nodular fasciitis (NF) is a self-limiting tumor that mostly occurs in the subcutaneous superficial fascia. NF originating from the appendicular periosteum is extremely rare. A large NF lesion of periosteal origin can be misdiagnosed as a malignant bone tumor and may cause overtreatment. CASE SUMMARY: A right axillary mass was found in a 46-year-old man and was initially diagnosed intraoperatively as low-grade sarcoma, but later diagnosed as NF after post-resection histopathological evaluation. Furthermore, fluorescence in situ hybridization analysis revealed a USP6 gene rearrangement that confirmed the diagnosis. To the best of our knowledge, this is the first case of NF in the humeral periosteum. CONCLUSION: NF poses a diagnostic challenge as it is often mistaken for sarcoma. Postoperative histopathological examination of whole sections can be combined with immunohistochemical staining and, if necessary, the diagnosis can be confirmed by molecular detection, and thus help avoid overtreatment.