PC1187: Massive Lymphadenopathy in COVID-19 and MIS-C Masquerading as a Retroperitoneal Tumor

Introduction: The coronavirus disease 2019 (COVID-19) pandemic has brought many challenges to pediatric care due to its atypical symptomatology. In May of 2020, the U.S. Centers for Disease Control and Prevention described multisystem inflammatory syndrome in children (MIS-C), which may present in association with a COVID-19 diagnosis. The wide range of presenting symptoms for COVID-19 and MIS-C can mimic many other diagnoses lending clinical challenges. We report a case of COVID-19 and MIS-C presenting with gastrointestinal complaints and massive retroperitoneal lymphadenopathy, mimicking an abdominal tumor.

Case Description: A 7-year-old girl with a documented asymptomatic COVID-19 infection one month prior to presentation developed clinical symptoms suggestive of appendicitis. On workup, ultrasound identified a retroperitoneal mass that was confirmed on an abdominal computed tomography (CT) scan. The mass was five centimeters and caused compression on the inferior vena cava (IVC). Due to concerns for an oncologic process, we sought to obtain tissue for diagnosis. A percutaneous needle biopsy was not possible, so she underwent an open exploration of the retroperitoneum via an extraperitoneal approach. The mass was found to arise within the root of the mesentery and was completely excised. Pathology demonstrated a lymph node with capsulitis, areas of geographic necrosis with fibrin, karyorrhexis and fibrin thrombi within small blood vessels. All cultures were negative. Flow cytometry showed no evidence of abnormal lymphoid cells. Her postoperative course was complicated by the development of cardiogenic shock on postoperative day one, consistent with the development of MIS-C and required intensive care unit (ICU) treatment for ionotropic support. After therapy with intravenous immunoglobulin (IVIG) and corticosteroids, she gradually improved and was discharged home on hospital day eleven.

Discussion: GI manifestations of MIS-C are becoming more commonly reported in the literature. A few similar cases have been reported presenting with symptoms of appendicitis, likely consistent with mesenteric lymphadenitis, but there have been no published reports of massive mesenteric lymphadenopathy. This case provides a unique clinical dilemma given the implications of monitoring a potentially malignant mass rather than obtaining tissue for further diagnosis. It is vital to ensure the appropriate clinical context when making diagnostic decisions by evaluating for either current or past COVID-19 infection regardless of symptoms.

Conclusion: The COVID-19 pandemic has presented a diagnostic challenge for clinicians given the wide range of presenting symptoms. To our knowledge, there have been no reported cases of lymphadenopathy due to COVID-19 or MIS-C mimicking a retroperitoneal tumor in the literature. We advocate for a multidisciplinary patient-centered approach to formulating a diagnostic and therapeutic plan when encountering massive lymphadenopathy in the setting of a current or past COVID-19 infection. Close monitoring may be preferred over biopsy to avoid unnecessary surgery.