Background: The fetal lung interstitial tumor (FLIT) is a newly identified tumor and is extremely rare, with only five reports published in English. Here, we report 4 cases of FLITs in China and present a literature review, aiming to explore this rare tumor.
Methods: The clinical and histological findings, immunophenotype, and ALK FISH of these 4 FLIT cases were evaluated, with a detailed review of the literature.
Result: The 4 cases comprised 2 male and 2 female infants. Two cases had a lung or intrathoracic mass during pregnancy, as early as 28 gestational weeks, and tachypnea and groaning shortly after birth. The other two cases received clinical attention because of jaundice and weakness at 3 days and 10 minutes after birth. The two female patients had a high serum AFP level. CT showed a well-
circumscribed solid-cystic mass in the lung. Surgical removal was performed at 6 days, 11 days, 18 days and 5 days respective. Grossly, the tumor was a well-0circumscribed, solid-to-spongy cut surface, and the largest diameter was 5.5-6.1 cm. Histological examination revealed an immature airspace and interstitium resembling fetal lung tissue at the canalicular stage (20-24 weeks of gestation). The epithelial cells coexpressed CK, EMA, TTF-1 and b-catenin, while the interstitial cells were strongly and diffusely positive for vimentin, with variable degrees of desmin, SMA, MSA and b-catenin. There was no ALK positivity among the four cases. One of the four cases had an ALK gene fusion by FISH. All four cases were in good condition after surgery.
Conclusions: The FLIT is a recently reported type of congenital lung lesion with distinct pathological morphology. Some of the FLIT cases have high AFP levels, which represents an ALK gene fusion and may be related to ALK-positive tumors. The FLIT prognosis is good, and surgery is the preferred treatment. The differential diagnosis should include congenital pulmonary airway malformation (CPAM), pleuropulmonary blastoma (PPB), congenital inflammatory myofibroblastic tumor (CIMT) and pulmonary interstitial glycogenosis (PIG).
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