The differential diagnosis for neonatal primary lung masses includes developmental anomalies and congenital lung tumors. Fetal lung interstitial tumor (FLIT) is a rare benign mesenchymal lesion which presents either antenatally or within the first 3 months of age. FLIT is a circumscribed solid-cystic mass which histologically resembles the fetal lung during the canalicular stage at 20-24 weeks of gestation. It is composed of immature mesenchymal cells expanding the interstitium and irregular airspace-like structures. Of all published cases, only 1 identified an α2-macroglobulin (A2M)::anaplastic lymphoma kinase (ALK) fusion and all cases underwent surgical resection in the neonatal or infancy period. We present the second case of FLIT with an A2M::ALK fusion diagnosed postnatally in a neonate which partially regressed spontaneously during conservative management with interim resection at 39 months of age, and provide a review of the literature.

中文翻译：

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新生儿 A2M::ALK 重排使胎儿肺间质性肿瘤自发部分消退。

新生儿原发性肺部肿块的鉴别诊断包括发育异常和先天性肺部肿瘤。胎儿肺间质瘤 (FLIT) 是一种罕见的良性间质病变，在产前或出生后 3 个月内出现。FLIT 是一种边界清楚的实性囊性肿块，其组织学类似于妊娠 20-24 周小管阶段的胎儿肺。它由扩张间质和不规则空腔样结构的未成熟间充质细胞组成。在所有已发表的病例中，只有 1 例鉴定出 α2-巨球蛋白 (A2M)::间变性淋巴瘤激酶 (ALK) 融合，所有病例均在新生儿或婴儿期接受了手术切除。我们介绍了第二例 FLIT 病例，该病例是出生后在新生儿中诊断出的 A2M::ALK 融合，在 39 个月大时进行临时切除的保守治疗期间部分自发消退，并提供了文献综述。