DISCUSSION
To this date, this hybrid SEF-LGFMS tumor with an EWSR1/CREB3L1 fusion has not been described in the literature as a primary lung neoplasm. Only one other EWSR1/CREB3L1 hybrid SEF-LGMS tumor has been reported, a 10-year-old primary renal tumor (7). The patient presented with widespread metastases, underwent biopsy and subsequent palliative chemotherapy; the patient died of metastatic disease 12 months after the diagnosis.
In contrast, the EWSR1/CREB3L1 gene fusion has been observed in 80-90% of SEF (a rare soft-tissue sarcoma) cases (8). The youngest patient reported with SEF and an EWSR1-CREB3L1 mutation was a 3-year-old who presented with numerous lung and bone metastases (8). In a case series of four pediatric patients with SEF in deep soft tissues of the trunk harboring EWSR1-CREB3L1 mutations, one patient did not receive further treatment and died 17 months after diagnosis, two remained disease-free post-surgery, and one remained disease-free 22 months following radiation and multiple chemotherapy cycles (9). A review of 51 SEF cases (4/51 pediatric) found that 10% of primary SEF tumors occurred in the lung, while 42.1% of metastatic tumors were found in the lung/pleura (10).
LGFMS is an indolent tumor with metastatic potential and has only been reported in 33 pediatric patients. As with hybrid SEF-LGFMS tumors, most LGFMS cases display FUS-CREB3L2 mutations; only four case reports thus far demonstrate EWSR1-CREB3L1 fusion mutations in LGFMS (with primary tumors of the orbit, lower leg, thigh, and kidney) (11,12). Of the two pediatric patients with EWSR1-CREB3L1 LGFMS, one presented with a subcutaneous nodule on the lower leg and is disease-free 12 months after excision; the other presented with a primary renal solid tumor and was disease-free 18 months post-surgical excision of solely the encapsulated mass (12).
This is only the second reported case of the use of robotic bronchoscopy in a pediatric patient. Though a specimen was obtained safely in our patient, it was not diagnostic, and an additional specimen was obtained surgically (13). There is a need for less invasive sampling of lung lesions in the pediatric population. Clinicians choose between surgical sampling and less often, flexible bronchoscopy with endobronchial or transbronchial biopsy. Robotic assisted bronchoscopy has recently joined this list as an option, due to its stability, adjustability, and peripheral visualization (14).
This unique case provides insight into the clinical and pathologic presentation of a EWSR1-CREB3L1 driven primary lung hybrid SEF- LGFMS, further broadening the molecular spectrum of pediatric lung tumors.
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