Evidence map›Paper›PMID 42687164›Full record

ArticleBMC pediatrics2026

Clinical features and imaging diagnostic challenges of fetus-in-fetu associated with abdominal cryptorchidism: a case report.

Xianlong Wu, Youqi Chen, Weiming Chen, Yongjuan Wei, Yangming Chen

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In one paragraph

Article in BMC pediatrics, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.

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4 · The record

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5 · Who and what money

Authors and funding

5 authors.

Xianlong WuDepartment of Pediatric Surgery, Quanzhou Maternity and Children's Hospital, No.700 Fengze Street, Quanzhou, Fujian Province, 362000, China.
Youqi ChenDepartment of Pediatric Surgery, Quanzhou Maternity and Children's Hospital, No.700 Fengze Street, Quanzhou, Fujian Province, 362000, China.
Weiming ChenDepartment of Pediatric Surgery, Quanzhou Maternity and Children's Hospital, No.700 Fengze Street, Quanzhou, Fujian Province, 362000, China.
Yongjuan WeiDepartment of Pediatric Surgery, Quanzhou Maternity and Children's Hospital, No.700 Fengze Street, Quanzhou, Fujian Province, 362000, China.
Yangming ChenDepartment of Pediatric Surgery, Quanzhou Maternity and Children's Hospital, No.700 Fengze Street, Quanzhou, Fujian Province, 362000, China. 649458756@qq.com.

Funding

No grant is acknowledged in the PubMed record.

6 · The paper itself

Abstract

backgroundFetus-in-fetu (FIF) is a rare congenital anomaly in which a malformed monozygotic twin is incorporated within its host twin. FIF is usually retroperitoneal, whereas association with an intra-abdominal undescended testis is exceptionally uncommon. Because imaging may show a heterogeneous mass containing soft tissue, fat and calcified elements, FIF can be difficult to distinguish preoperatively from mature teratoma, especially when cryptorchidism is also present. CASE PRESENTATION: A 3-day-old male neonate was admitted because of jaundice and a palpable right abdominal mass. Physical examination revealed an underdeveloped right hemiscrotum without a palpable right testis; the left testis was palpable and a left hydrocele was suspected. Prenatal ultrasound demonstrated a mixed echogenic mass in the right lower abdomen and raised the possibility of FIF. Fetal magnetic resonance imaging (MRI) and postnatal contrast-enhanced computed tomography (CT) showed a well-circumscribed cystic-solid abdominal mass with fat-like signal/density and multiple calcified stripe-like components, leading to diagnostic uncertainty between FIF and teratoma. Serum alpha-fetoprotein (AFP) and human chorionic gonadotropin (HCG) showed no abnormal elevation after interpretation according to neonatal age. Exploratory laparotomy revealed a 5.0 cm x 4.0 cm x 4.0 cm encapsulated cystic-solid mass arising from the right intra-abdominal undescended testis, without identifiable viable right testicular parenchyma. The mass and the atrophic right testicular/epididymal tissue were excised. Gross and histopathological examination demonstrated an organized axial skeleton/spinal structure and multiple differentiated tissues, including brain, intestine, liver, bone, skeletal muscle, skin, and epididymal duct tissue, fulfilling the Willis criterion for FIF.

conclusionsThis case highlights a very rare presentation of FIF associated with abdominal cryptorchidism. Recognition of calcified axial skeletal elements, fat components, organoid structures and the relationship to the spermatic cord/testicular structures may help pediatric surgeons and radiologists anticipate FIF rather than misdiagnosing the lesion as a testicular or abdominal teratoma. Complete surgical excision and long-term follow-up with ultrasonography and tumor markers are recommended.

Indexed as

CryptorchidismFetus-in-FetuDiagnosis, DifferentialHumansInfant, NewbornMagnetic Resonance ImagingMalePregnancyTeratomaTomography, X-Ray ComputedUltrasonography, PrenatalAbdominal massCase reportCryptorchidismFetus-in-fetuTeratomaUndescended testis

Identifiers

PMID42687164
PMCPMC13539875

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Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.