Out of Hand, Out of Control—Fibrous Hamartoma of Infancy of the Hand: A Case Report

Background: Fibrous hamartoma of infancy (FHI) is a rare benign tumor typically found in the axilla or trunk. Distal extremity involvement is exceptional. We present the first documented case of FHI of the hand in the Philippine literature, highlighting the conflict between oncologic clearance and functional preservation. Case Presentation: A 7-month-old male presented with an enlarging hypothenar mass. Initial ultrasonography revealed a heterogenous mass with intralesional cystic spaces, leading to a misdiagnosis of hemangioma despite the absence of significant flow on Doppler interrogation. Propranolol treatment failed. MRI revealed a poorly encapsulated mass encasing muscles, raising suspicion for malignancy. Intraoperatively, the tumor appeared as matted tissue with nondelineated borders, encroaching on neurovascular structures. To preserve hand function, a subtotal excision was performed rather than radical en bloc removal. Histopathology confirmed the triphasic components diagnostic of FHI. Conclusion: Local recurrence was noted 6 months postoperatively before the patient was lost to follow-up. This case underscores the diagnostic challenge of FHI in the hand due to vascular mimicry. Furthermore, the tumor's infiltrative nature in complex anatomy forces a difficult trade-off: Radical excision offers cure but risks functional devastation, whereas functional preservation carries a high risk of recurrence.