LAUSR

Abstract Rationale: Fibrous hamartoma of infancy (FHI) is a rare benign soft-tissue tumor in children with a triphasic organoid histologic appearance. Patient concerns: We here report a case with the largest FHI published so far. A 13-month-old boy with a rapidly growing tumor 45 cm in length and 69.3 cm in circumference of the left lower extremity was identified immediately at birth. Diagnoses: The diagnosis was uncertain before the operation, although biopsy was conducted. The postoperation histological examination showed arranged spindle cells, adipose tissue, and nests of immature small cells embedded in a myxoid background, which is the characteristic triphasic histology of FHI. Interventions: Under general anesthesia, hip and lower extremity amputation was performed. Outcomes: The patient was followed-up for 6 years and no signs of recurrence were found, suggesting a favorable prognosis, although a part of the residual tumor was present after the surgery. Lessons: FHI exhibits pathological and clinical characteristics. However, differential diagnosis of FHI from other soft-tissue tumors before operation remains a challenge. Thus, sometimes, aggressive therapy for the treatment of FHI might be a good choice to get a satisfactory.