Abstract
Congenital perianal lipoma is a rare benign tumor in infants, often requiring careful differential diagnosis from more complex lesions like sacrococcygeal teratoma. This report details the presentation, imaging, and management of a congenital perianal lipoma in a 55-day-old infant. A 55-day-old infant was referred with a perianal mass initially identified on prenatal ultrasound. Physical examination revealed a soft, palpable mass approximately 2 cm superior to the anal verge. Targeted postnatal ultrasonography demonstrated a well-circumscribed, homogeneous, spindle-shaped mass with no connection to deep pelvic structures, the rectum, or the spine, and no associated spinal anomalies. The infant underwent complete, sphincter-sparing surgical excision. Histopathological examination confirmed the diagnosis of a lipoma, composed of mature adipose tissue. The postoperative course was uneventful, with preserved urinary and bowel function. This case illustrates that in a prenatally suspected perianal mass, a connection-focused imaging pathway, primarily using high-resolution ultrasound to exclude deep extensions, can effectively support the diagnosis of an isolated congenital lipoma. Complete local excision with sphincter preservation is the definitive and function-sparing treatment, yielding an excellent outcome.