Not only vascular lesions: a case report of infantile fibrosarcoma.

Objectives: To present a rare case of congenital infantile fibrosarcoma (IFS) mimicking a vascular anomaly and to emphasize the diagnostic value of color Doppler and contrast-enhanced ultrasound (CEUS) in differentiating IFS from benign vascular tumors such as congenital hemangioma.

Materials and methods: We present the case of a 4-month-old male with a congenital lumbosacral mass initially suggestive of congenital hemangioma. Ultrasound and Doppler examination demonstrated a highly vascularized lesion; however, the imaging findings remained equivocal for a definitive diagnosis of hemangioma. MRI confirmed a solid, hypervascular lesion without spinal involvement. Histopathology identified a spindle cell neoplasm consistent with IFS, likely driven by an NTRK rearrangement. The mass was surgically excised with a good postoperative recovery.

Results: Doppler and CEUS findings showed vascular features atypical for congenital hemangiomas, which generally present with diffuse, centripetal enhancement and sustained contrast uptake. In contrast, this lesion exhibited an organized radial vascular pattern with early unidirectional enhancement and rapid washout. However, imaging findings remained equivocal for a definitive diagnosis of hemangioma, necessitating further histopathological evaluation, leading to timely surgical management.

Conclusions: This case underscores the diagnostic challenge in distinguishing IFS from benign vascular tumors and highlights the importance of histological evaluation. Early recognition is essential, as IFS, though locally aggressive, has a favorable prognosis when promptly and properly managed.