Fetus in Fetu Presenting as a Second Head: A Rare Case Report with Pathologic Correlation

Fetus in fetu (FIF) is a rare congenital anomaly in which a malformed parasitic twin is enclosed within its host, usually in the retroperitoneum. Oral presentation is extremely rare, with few cases described. Differentiation from teratomas, particularly epignathus, is challenging but crucial for prognosis and management.

An 18-year-old gravida 3, para 2 was referred at 26 weeks for suspected epignathus. Ultrasound showed a large oropharyngeal mass, polyhydramnios, omphalocele, diaphragmatic hernia, and cardiac anomalies. Fetal demise occurred at 32 weeks. Postmortem examination revealed a second head-like mass with skin, cranial bones, facial features, and cerebral tissue. Histopathology confirmed highly organized fetiform mass consistent with FIF despite absence of vertebral axis.

This is a rare case of oral FIF entirely comprising a second head and associated with major host anomalies. Awareness of this entity is essential for accurate diagnosis and perinatal planning when airway compromise is anticipated.