Presentation of congenital soft-tissue sarcomas: A single institution experience.

Abstract

e23551 Background: Pediatric sarcomas make up 10% of pediatric tumors and involve a varied range of histological patterns with different prognosis which creates therapeutic challenges. Neonatal presentation is rare among sarcomas and poses further challenges in therapy. Methods: We present 5 cases of congenital sarcomas reporting pathology, genetics, treatment, and outcomes. We retrospectively identified 5 patients with sarcomas diagnosed in the neonatal period from a single institution in Miami from 2017 – 2022 in order to identify similarities between neonatal sarcomas. Our sarcomas included an embryonal rhabdomyosarcoma (RMS), infantile fibrosarcoma (IFS), rhabdoid tumor, and two undifferentiated sarcomas. Results: The presentation occurred between birth and four days old. Location at presentation was varied. Four of our patients were Nonrhabdomyosarcoma Soft Tissue Sarcomas (NRSTS). Only one patient was diagnosed prenatally, while three were diagnosed at birth, and one at 4 days of life. Three patients presented spindle cell pathology. One of our undifferentiated sarcomas was classified as IFS-like, Archer FusionPlex was negative for mutation. Our other undifferentiated sarcoma showed a COL1A1 gene rearrangement on chromosome 17q.21 with immunostains positive for BCOR, SMARCB1, SMARCA4. Congenital fibrosarcoma showed ETV6 fusion with NTRK and immunostains positive for FLI-1, SMA, CD34, INI-1. The RMS showed focal loss of PTCH1 and FANCC and had immunostains positive for desmin and myogenin. The metastatic rhabdoid tumor showed SMARCB1 whole gene deletion as well as a 570kB deletion in chromosome 22q11.23. Three patients were treated on ARST 0331 with vincristine, doxorubicin, and cyclophosphamide (VAC), with the undifferentiated sarcoma requiring advancement to ARST 0332. The patient with metastatic rhabdoid tumor was treated with AREN 0321. Four patients required surgery. We had 1-year-survival in three patients, all treated on ARST 0331 or ARST 0332. The patient with metastatic rhabdoid tumor died at 4 months of age while on AREN 0321, and our patient with IFS-like sarcoma decompensate and died at ten days old, prior to starting therapy. Conclusions: We show multiple genetic mutations with SMARCB1 alteration in both an undifferentiated sarcoma and a malignant rhabdoid tumor but otherwise found no significant pattern among individual sarcomas. Our cases show good outcomes for patients qualifying for ARST 0331. We highlight the need for improved methods of detection of pediatric tumors in utero.