Extranodal Nasal Type NK/T-Cell Lymphoma of the Transverse Colon With Gastrointestinal Perforation in a 15-Year-Old: Durable Remission With Modified SMILE Chemotherapy and HSCT.

NK/T-cell lymphoma (NKTCL) is an aggressive lymphoma associated with Epstein-Barr virus (EBV), with higher incidence in Asian populations. Typically, patients present in their fifth decade with extranodal disease in the upper aerodigestive tract. Pediatric NKTCL is rare, with no established pediatric standard of care treatment. We describe the case of a healthy 15-year-old Filipino-Canadian male who presented with transverse colon perforation and was diagnosed with extranodal EBV + nasal type NKTCL of the gastrointestinal (GI) tract. After a complicated initial surgical course, we elected to treat him using six cycles of modified SMILE (dexamethasone, PEG-asparaginase, ifosfamide, and etoposide) chemotherapy and consolidative hematopoietic stem cell transplant (HSCT). The post-HSCT course involved cytomegalovirus reactivation (buccal lesions, viremia); adenovirus reactivation (positive nasal swab, viremia); zoster reactivation; acute and chronic oral/upper GI graft-versus-host disease (GVHD); chronic skin GVHD (vitiligo); and avascular necrosis. At the most recent follow-up, surveillance imaging and investigations at 2 years post-transplant showed durable CR1 and 100% donor chimerism. To our knowledge, this is the fourth reported case of primary GI NKTCL in a pediatric/adolescent patient; the only patient treated with an asparaginase-containing regimen; and the only patient to undergo consolidative HSCT. Our patient's outcome supports the utilization of an aggressive approach to treat GI NKTCL in young, fit patients similar to Stage III/VI nasal NKTCL. Our case also highlights unique treatment considerations for adolescent cancer patients, including delayed diagnoses and lack of standardized protocols.