Fibrous Hamartoma of Infancy of the Arm Mimicking a Vascular Malformation: A Diagnostic Pitfall.

Background: Fibrous hamartoma of infancy (FHI) is a rare benign soft tissue tumor of early childhood, often misdiagnosed due to its clinical and/or radiological resemblance to vascular malformations or pediatric soft tissue neoplasms. Case Presentation: A 7-month-old male presented with a rapidly enlarging, firm, non-pulsatile subcutaneous mass involving the anterior aspect of almost the entire right arm. MRI suggested a low-flow vascular malformation; however, due to clinical concern for alternative pathology and the lesion's benign appearance, large size, superficial location, and resectability, complete excision was performed. Histopathology revealed the characteristic triphasic pattern confirming fibrous hamartoma of infancy. The patient recovered well with no recurrence at 3-month follow-up. Conclusion: This case highlights the diagnostic pitfalls of FHI, which may closely mimic vascular anomalies on imaging, and underscores the importance of surgical excision for both definitive diagnosis and curative treatment. To our knowledge, this represents the first reported case of FHI from Palestine.