C80-25 Bone Marrow Metastasis as the Initial Presentation of Small Cell Lung Carcinoma: A Diagnostic Challenge

Abstract Case Presentation A 72-year-old man with a medical history of hypertension and prior stroke was admitted with recurrent hemoptysis, acute hypoxic respiratory failure, and newly detected left infra-hilar mass. Laboratory evaluation revealed severe normocytic anemia (hemoglobin 6 g/dL) and thrombocytopenia (platelet count 55 ×109/L) without evidence of overt bleeding aside from mild hemoptysis. Despite receiving 5 units of packed red blood cells and platelet transfusions, his count remained refractory. Chest CT demonstrated a 5.4 cm left lower lobe infra-hilar mass extending into the mediastinum with significant mediastinal and left hilar lymphadenopathies, raising concern for malignancy. Diagnostic bronchoscopy/endobronchial ultrasonography with biopsies form the mass, hilar and mediastinal lymph nodes were done. Two days later, the patient developed worsening hemoptysis requiring cryotherapy for endobronchial lesions, left mainstem endobronchial blocker placement, and inhaled tranexamic acid therapy. The pathology result including immunohistochemistry confirmed small cell adenocarcinoma with the involvement of right-side mediastinal nodes. Evaluation for thrombotic microangiopathy was negative, and reticulocyte count was low, suggesting bone marrow suppression. Given persistent cytopenias, a bone marrow biopsy was performed and demonstrated metastatic small cell carcinoma involving approximately 30% of the marrow space. The flow cytometry confirmed CD56 positivity with high FSC (forward and side scatter) consistent with metastatic small cell carcinoma. Brain MRI showed no intracranial metastases. The patient received palliative radiation therapy to the left hilum and mediastinum (850 cGy/1700 cGy) but ultimately transitioned to comfort-focused care. Discussion Bone marrow metastasis as an initial presentation of small cell lung carcinoma (SCLC) is uncommon and often portends a poor prognosis. This case highlights the diagnostic complexity when cytopenias precede a confirmed pulmonary diagnosis. While bronchoscopy remains the standard diagnostic approach for suspected lung malignancy, bone marrow biopsy in patients with unexplained anemia and thrombocytopenia may expedite diagnosis and management, especially when invasive pulmonary procedures pose additional risks. Early bone marrow evaluation in such settings could reduce diagnostic delays and facilitate timely therapeutic intervention. Conclusion This case underscores the importance of considering bone marrow biopsy as an early diagnostic step in patients presenting with cytopenias and a radiographic lung mass. Awareness of this rare presentation of SCLC with bone marrow involvement is crucial to avoid delays in diagnosis and optimize patient outcomes. This abstract is funded by: NA