Congenital Bilateral and Multifocal Mesenchymal hamartoma of the chest wall: A Case in a Neonate and Differential Diagnosis

Abstract

Background:Mesenchymal hamartoma of the chest wall(MHCW) is a rare benign extrapleural lesion that arises from rib or spine of neonates or early infancy, and commonly presents as a unilateral mass. Here, we describe a rare case of bilateral and multifocal MHCW in the right 5th rib and the left 11-12th thoracic and 1st lumbar vertebrae.Case presentation:A male neonate of 3700g weight transferred to our hospital with mild respiratory distress and an asymptomatic, progressively enlarging intra-thoracic mass. Computed tomography scan(CT) and magnetic resonance imaging(MRI) indicated a large well-circumscribed, heterogeneous enhancing mass, arising from the posterior-medial aspect of the right chest wall, involving 3-5th posterior ribs. Other smaller sizes lesions observed in vertebral arch and transverse process of the left 11-12th thoracic and 1st lumbar vertebrae. The thoracotomy with en bloc resection of the mass and the 5th rib was performed. Microscopically, the lesion was cystic and solid, consisted of hyaline cartilages, mesenchymal cells, and various-sized hemorrhagic spaces. Immunohistochemically, the cartilages and mesenchymal cells were positive for S-100, Smooth Muscle Actin(SMA), CD163 and CD68. The epithelium cells of aneurysmal bone cyst(ABC)-like were negative for CD34. Ki-67 estimated at 5%-10%. Fluorescence in situ hybridization(FISH) was negative for USP6 gene break-apart probe, which ruled out primary ABC. At 8-month follow-up postoperatively, the right chest walls with no sign of recurrence and the lesions of left vertebral arch and transverse process were stable, no increased in size.Conclusion:The bilateral and multifocal MHCW is considerably rare and related clinical research is limited. Fortunately, we clearly observed the tumor’s origin, growth process from the earlier pregnancy to delivery, different effects during the fetal periods, and differential diagnosis. This report may raise awareness regarding the MHCW.