Infantile Fibrous Hamartoma: A Rare Case of a Paraumbilical Subcutaneous Mass in a One-Year-Old Male

Infantile fibrous hamartoma (FHI) is a benign soft tissue tumor that primarily occurs in infants. We present the case of a one-year-old male with a paraumbilical subcutaneous mass. Clinical differentials included lipoma versus paraumbilical hernia. Ultrasound revealed a hypoechoic, elongated, poorly defined nodule in the right upper anterior abdominal wall, while immunohistochemistry showed positivity for BCL2, smooth muscle actin (SMA), and cytoplasmic β-catenin. Surgical excision and pathological examination revealed an ill-defined lesion composed of abundant mature adipose tissue interspersed with densely hyalinized fibrous tissue. Paraumbilical FHI can clinically mimic a lipoma or a small hernia. Correlation with targeted ultrasound assists in excluding hernia and guiding surgical management. Surgical removal is generally curative, with a low recurrence rate. This case contributes to the literature on FHI and underscores the importance of considering this entity in the differential diagnosis of subcutaneous masses in infants.