A retrospective analysis of initial ultrasonographic misdiagnosis of fibrous hamartoma of infancy at the ultrasound center of a tertiary hospital in China.

Background: Fibrous hamartoma of infancy (FHI) is a relatively rare fibroblastic or myofibroblastic tumor. FHI is highly prone to misdiagnosis prior to surgery owing to its nonspecific clinical features and imaging manifestations. We analyzed the potential factors associated with initial ultrasonographic misdiagnosis of FHI to improve the understanding and diagnostic accuracy of FHI and reduce the misdiagnosis rate among pediatricians and sonographers. Methods: We retrospectively analyzed all consecutive children with FHI at Anhui Provincial Children's Hospital between January 2012 and December 2025. The clinical characteristics, ultrasonographic features, and CT/MRI imaging findings of FHI were summarized, and potential factors associated with initial ultrasonographic misdiagnosis were analyzed. Results: Sixteen children and 17 lesions were included in this study. Fifteen children (15/16, 93.75%) were under 2 years of age, and the male-to-female ratio was approximately 3:1. Ultrasonographic examination revealed that three lesions (3/17, 17.65%) were hypoechoic, two (2/17, 11.76%) were mixed echoic, and 12 (12/17, 70.59%) were principally hyperechoic, of which two (2/17, 11.76%) manifested a "fence-like pattern", and six (6/17, 35.29%) exhibited a "serpentine pattern". All 16 children were initially misdiagnosed on preoperative ultrasonography. Lipoma accounted for the largest proportion (8/16, 50%), followed by infantile hemangioma (3/16, 18.75%). All 13 children who underwent CT/MRI were also misdiagnosed. Qualitative ultrasound-histopathology correlation suggested that hyperechoic lesions were mainly associated with mature adipose tissue, whereas hypoechoic lesions were mainly associated with primitive mesenchymal tissue. Follow-up data were available for five children (median, 76 months), and no local recurrence was observed. Conclusions: FHI is frequently misdiagnosed on ultrasonography. The "serpentine pattern" and "fence-like pattern" may be suggestive ultrasonographic manifestations of FHI. The proposed diagnostic flowchart, which emphasizes integrative interpretation of clinical characteristics and multimodal imaging findings, may assist pediatricians and sonographers in differentiating FHI from other soft-tissue lesions. However, a definitive diagnosis still relies on histopathological examination.