The patient was a 72-year-old woman with a history of smoking (50 pack-years), alcoholism and extrinsic asthma who consulted for fever, productive cough and an increase in her usual dyspnoea. Physical examination revealed fever (37.9º C), tachypnoea and hypoventilation with expiratory wheezing. No visceromegaly or adenopathies were palpable.
Laboratory tests showed a mild neutrophilia and mild thrombocytopenia, and sputum culture and Gram and Ziehl-Neelsen stains were negative. Chest X-ray showed a left paracardiac condensation, with air bronchogram, blurring the cardiac silhouette and computed axial tomography (CT) confirmed the existence of a left pulmonary infiltrate, with pleural involvement. With the suspected diagnosis of lingula pneumonia, treatment was started with bronchodilators, oxygen therapy and amoxicillin-clavulanic acid, with clinical improvement and disappearance of the febrile fever. The patient was discharged for follow-up in the pneumology department where, given the persistence of the condensation image, the study was continued. Bronchoscopy showed non-specific inflammatory signs in the left bronchial tree with normal right bronchial tree; cytology of bronchial aspirate and bronchial brushing was negative for malignancy. CT-guided fine needle aspiration (FNA) showed a monomorphous lymphoid proliferation, suspicious for non-Hodgkin's lymphoma (NHL). A lung biopsy by mini-thoracotomy confirmed the diagnosis of CD 20 positive, bcl-2 positive, p-53 negative small B-cell lymphocytic lymphoma (SBCL).

Biological studies showed a discrete increase in ESR, b2-microglobulin and the presence of a minimonoclonal IgM lambda band in the proteinogram. Viral serology and autoimmunity study (ANOES) were negative. Abdominal ultrasound showed incipient signs of diffuse chronic liver disease and abdominal CT showed no adenopathy. A new thoracic CT scan confirmed the presence of a dense, homogeneous, 5x7 cm, triangular-shaped lung mass with peripheral base and pericardial apex, involving the lingula and left upper lobe, accompanied by an atelectasis component with mediastinal deviation. Bone biopsy ruled out lymphoma infiltration.
With the diagnosis of low-grade primary pulmonary lymphoma (PLL), oral treatment was started with pulsed chlorambucil, 40 mg orally on day 1, and prednisone, 100 mg/day for 4 days, every 4 weeks. At the first re-evaluation, after four cycles of chemotherapy, the size of the tumour mass had not changed, so treatment with intravenous polychemotherapy was proposed to the patient, which she refused. Continuous chlorambucil was then started at a dose of 3 mg/day. A new chest CT scan showed a decrease in the diameter of the lung mass of more than 50% (8 months later) and more than 75% (16 months after starting daily treatment). Side effects included haematological and hepatic toxicity, both WHO grade I, and the dose of chlorambucil was reduced to 1 mg/day. After two years of continued treatment, chest X-ray and CT scan showed well-ventilated lung parenchyma, with only some residual fibrous tract in the left lung. A gammagraphic study with gallium-67 showed hyperactivity in the middle third of the left hemithorax, confirming the existence of residual disease. Despite this, the patient has remained in therapeutic abstinence, in very good partial remission (VBPR) and progression-free to date (progression-free interval of 53 months).

