Abstract
<title>Abstract</title> <p> Thymomas and lymphomas usually occur separately but their diagnosis is a well-recognized challenging pitfall owing to their common location and overlapping morphohistology. They present as anterior mediastinium mass with epithelial-lymphoid admixtures and lymphocyte-rich patterns respectively. We report a case of incidental discovery of an anterior mediastinal mass thought to be thymoma but later revealed by immunohistochemistry (IHC) as PMBCL (Primary Mediastinal Large B-cell Lymphoma). <bold>Background</bold> : Differentiating thymic lymphoma from thymoma is one of the most clinically consequential diagnostic challenges in anterior mediastinal pathology, as misdiagnosis can lead to inappropriate surgery (for lymphoma) or delayed resection (for thymoma). The key pitfalls span imaging, histopathology, and immunohistochemistry. The thymus, one of two primary lymphoid organs, contains both epithelial and lymphoid cells. Accurate clinical distinction can be challenging owing to their common location and gross appearance, is essential with far-reaching clinical consequences(2). Our case is among a handful of published reports detailing such challenges of diagnosis of thymoma and lymphoma. <bold>Case Presentation</bold> : Case of 32 year old female, history of Endometrial Carcinoma status post hysterectomy, Bilateral Salpingophorectomy(BSO) and Lymph Node dissection brought in by Emergency medical services (EMS) as a Trauma code, gunshot wound(GSW) injury to the abdomen, unresponsive and in hemorrhagic shock. Patient intubated, resuscitated and emergently taken for Exploratory Laparotomy. Finding on postoperative imaging revealed a 3.5cm right prevascular anterior mediastinal mass suggestive of thymoma or lymphoma.owing to retained bullets, a Magnetic Resonance Imaging was not obtained. Patient evaluated at outpatient cardiothoracic clinic, discussed surgical excision of mass based on an imaging review and report to obtain tissue diagnosis. Biopsy obtained via a median sternotomy with intraoperative findings of ~ 5–6 cm extra pericardial anterior mediastinal mass with no involvement of lungs or brachiocephalic vessels. An intraoperative surgical pathology was noted as thymoma, lymphocytic. A final surgical pathology review at an outside facility favored final diagnosis of CD20 + primary mediastinal large B-cell lymphoma. Patient referred to an oncologist for additional workup and management. Nuclear medicine imaging report showed no metabolically active disease. Patient immediately started on a dose-escalated six cycles of chemotherapy regimen. A three-month postop follow-up revealed patient was clinically stable with ongoing chemotherapy sessions. <bold>Conclusion</bold> : Lymphoma, diagnosed as thymoma is not quite uncommon owing to their common gross presentation. The availability of cytoarchitecture, nuclear imaging and emerging scientific technologies have improved the challenging hurdle of diagnosis, thus impacting the direction of treatment strategies. Our case will thus add to the body of research that already exists to raise the awareness of such clinical scenarios or instances, especially in the differential diagnoses of thymomas and or lymphomas. </p>