Lymphoma presenting as chronic nonproductive cough misdiagnosed as lung cancer recurrence: a case report

Chronic nonproductive cough is a common initial symptom prompting patients to seek medical attention. Its etiology is complex and broad, often posing diagnostic challenges in clinical practice. A woman with a history of resected double primary lung cancer experienced a persistent dry cough for over 2 months. Chest computed tomography (CT) revealed multiple enlarged lymph nodes in the mediastinum and right subclavian region. Pulmonary function tests suggested possible concomitant cough variant asthma. Positron emission tomography-computed tomography (PET-CT) suggested lung cancer recurrence with metastasis. However, endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) biopsy of the mediastinal lymph nodes showed no malignant cells. Anti-asthma and anti-lung cancer therapies failed to alleviate the dry cough. Ultimately, she was diagnosed with diffuse large B-cell lymphoma (DLBCL) by a left supraclavicular lymph node excisional biopsy. Following lymphoma treatment, her cough resolved and the enlarged lymph nodes regressed. This case highlights that in patients with chronic nonproductive cough post-lung cancer treatment, even when imaging suggests possible recurrence, second primary malignancies (SPMs) such as lymphoma should be considered. Pathological confirmation remains essential.