Background: Malignant Small round Cell Tumor (MSRCT) is very rare group of tumors. Malignant cells have similar histologic appearance making it difficult to distinguish one from another, and poses a diagnostic challenge with needs for a multimodal approach. Immunohistochemistry and immunophenotyping by flow cytometry, reverse transcriptase polymer chain reaction (RTPCR) and fluorescence in situ hybridization are needed to confirm. The appropriate and best treatment in early stages of MSRCT is early surgical excision with chemoradiotherapy based on patient specification. Inspite of all these, tumors have poor prognosis and chance of recurrence are high. Method: Case study of a 27-year-old male who presented with a non-productive cough for 4 weeks, with feverish feeling with weight loss and shortness of breath and a new onset precordial chest pain non radiating and worse on exertion. On examination his vitals were: BP 121/91 mm of hg, pulse rate 114bpm, temperature 36.3 degrees Celsius, respiratory rate 24/per min, SPO2 96%.On examination, Elevated Jugular Venous Pressure, hyperactive precordium, displaced apex beat to 6th intercostal space anterior axillary line, muffled heart sounds and bilateral lower limb edema. Respiratory exam was unremarkable. Sputum gene expert was negative for mycobacterium tuberculosis and covid 19 rapid test was negative. Chest X Ray showed cardiomegaly and a transthoracic echocardiography revealed moderate-large pericardial effusion, with mild collapse of right atrium in diastole. Pericardiocentesis done showed hemorrhagic effusion with lymphocytes cell component, patient was initiated on treatment for TB pericarditis empirically. Three months later a chest CT scan done revealed extensive mediastinal/pericardial mass with lung nodules. An ultrasound guided mediastinal/Pericardial biopsy was done, revealed a poorly differentiated small round cell carcinoma. Results: Patient expired 14 weeks from the initial onset of symptoms while awaiting immunohistochemistry studies for specific diagnosis of the tumor and oncology review. Discussion: This demonstrates the complexity of establishing differential diagnosis of MSRCT in a resource limited setting with subsequent delay in treatment initiation, heralds poor prognosis. This also confirms difficulties in establishing differential diagnosis in poorly differentiated tumor.