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Título

Fetus in Fetu: Intra-abdominal Fetal Mass. Case Report

Descrição sucinta do(s) objetivo(s)

The objective of this presentation is to display and correlate imaging findings from fetal magnetic resonance (fMR) imaging and ultrasound (US) in a rare prenatal condition known as Fetus in fetu (FiF).

História clínica

A 28-year-old patient, undergoing her second pregnancy, with no pathological or toxic clinical history, presented with an intra-abdominal fetal mass identified during a 34-week gestational age routine ultrasound. A Fetal Magnetic Resonance Imaging was performed, revealing findings compatible with FiF.

Discussão e diagnóstico

With an estimated incidence of 1 in 500,000 births, FiF is a condition in which, due to abnormal embryogenesis in a monochorionic diamniotic pregnancy, one fetus grows abnormally within the body of the other. The diagnosis is based on imaging findings and is characterized by the presence of a separate vertebral column and the development of organs around this axis, indicating an early stage of fetal development. These features distinguish it from a highly differentiated Teratoma.

In this case, the US examination revealed the finding of an intraperitoneal mass in the middle of the fetal abdomen, solid, heterogeneous, with fatty areas and calcified structures resembling long bones. Presented vascularization by a branch of the superior mesenteric artery and displaced abdominal organs without invading them. These findings were confirmed later with fMRI.
Birth was delivered via cesarean section at 38 weeks. Due to suspicion of FiF vs. Teratoma (Tt), tumor markers were tested with negative results. During follow-up, FiF growing was observed, leading to the decision to surgically remove the tumor at two months of age. Anatomopathologic examination confirmed the diagnosis of FiF. A computed tomography of the surgical specimen revealed characteristic FiF signs.

Conclusões

Imaging plays a crucial role in the diagnosis of this anomaly due to its similarity to a Tt, which can have malignant potential. Although it is a benign condition, the mass can affect surrounding structures. Prenatal diagnosis is more feasible nowadays, and suspicion should arise when an encapsulated cystic mass with calcified components is identified. Surgical treatment is required, and early detection allows for a favorable prognosis.

Palavras Chave

Fetus in fetu; Fetal MRI; Prenatal

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