November 2025, Volume 3, Issue 11

Author

Supriya Adiody and Anjaly Anoopkumar

Abstract

Background: Pulmonary neuroendocrine tumors (NETs) encompass a wide spectrum, ranging from well-differentiated neuroendocrine tumors (NETs: typical and atypical carcinoids) to poorly differentiated, high-grade neuroendocrine carcinomas (NECs: small cell lung carcinoma [SCLC] and large cell neuroendocrine carcinoma [LCNEC]). Accurate classification is critical for appropriate management. Case Presentation: A 75-year-old male with COPD and recurrent cerebrovascular accidents presented with progressive dyspnea, cough with mucoid expectoration, and low-grade fever. Imaging revealed a large mediastinal mass encasing the right pulmonary vessels with metastatic lung changes. CT-guided biopsy showed a malignant neoplasm with necrosis, high mitotic activity, and a Ki-67 index of 62%. Tumor cells expressed TTF-1, synaptophysin, and chromogranin, consistent with high-grade pulmonary NEC. NETs were excluded; morphology favored a differential diagnosis of SCLC versus LCNEC. Conclusion: This case highlights the diagnostic challenge of differentiating pulmonary NEC subtypes. Integration of morphology and immunohistochemistry is essential, as therapeutic strategies diverge markedly from those used for NETs.