An Unexpected Journey of Pediatric Hodgkin's Lymphoma Diagnosed via Pericardial Cytology: An Educational Case Report.

Hodgkin's lymphoma (HL) is a recognized hematological malignancy that typically appears in two specific age groups: the first peak occurs between 15 and 40 years of age, while the second peak arises in individuals aged over 60. While typically presenting as a mediastinal mass, rarer initial presentations include cardiac tamponade. In this case, we report a pediatric patient with HL presenting with massive pericardial effusion in the emergency department. We emphasize how a simple cytology test can facilitate diagnosis in such cases and discuss the role of cytological evaluation in guiding management. A 13-year-old male presented to our institution with fever and breathlessness. Radiological examinations indicated a mediastinal mass lesion. An emergency echocardiogram revealed pericardial effusion, which was subsequently drained and sent for cytological evaluation. Cytology revealed large atypical cells characterized by abundant cytoplasm, large nuclei, and prominent nucleoli, corresponding to Reed-Sternberg cells. Immunocytochemistry (ICC) on the cell block further confirmed the diagnosis of HL. Treatment commenced following biopsy confirmation, yielding favorable prognostic results from the patient's perspective. The primary goal of presenting this case is to underscore the unusual early presentation of HL and to illustrate how a simple test, combined with comprehensive diagnostic reasoning, can enable early diagnosis and enhance prognostic outcomes. Furthermore, we highlight the crucial role of ICC in the timely identification of this condition.