Pleural effusion masquerading as pseudotumor.

Sir,

A 52-year-old female patient presented with fever for 40 days and progressive breathlessness for a week. Examination identified tachypnea, tachycardia and signs of right pleural effusion. Complete blood count, blood sugar, renal function tests, serum electrolytes and liver function tests were normal. Serum brain natriuretic peptide was 60 pg/ml (normal < 100 pg/ml). Anti-nuclear antibody, anti-ds deoxyribonucleic acid, rheumatoid factor and testing for human immunodeficiency virus were negative. Bed side chest X-ray [Figure 1] showed homogenous opacities over right lower zone, right para-tracheal region and a mass lesion with convex margins in the right mid-zone. Echocardiogram was normal. Computerized tomography of chest showed loculated pleural effusion in anterior and posterior aspect of right hemithorax [Figure 2] and mass with convex margin in the reconstructed film [Figure 3]. The posterior spherical collection mimicked a tumor. Pleural fluid analysis revealed exudative effusion with lymphocyte predominance. Pleural fluid adenosine deaminase was 120 U/L (normal < 40 U/L) and cytology was negative for malignant cells. Polymerase chain reaction testing for tuberculosis was negative. In view of prolonged fever, exudative lymphocyte predominant pleural effusion (no evidence of malignancy or connective tissue disorder) and elevated adenosine deaminase she received empirical anti-tubercular drugs. No diuretics or steroids were administered. The pseudo-tumor due to pleural effusion vanished after 4 weeks of treatment. Pleural fluid culture was sterile at 4 weeks.

Figure 1

Chest X-ray showing a mass lesion in the right mid-zone with convex margins and homogenous opacities over right lower zone and right para-tracheal region

Figure 2

Computerized tomography-thorax (mediastinal window) showing pleural based opacities on the posterior and anterior aspect. The posterior located abnormality is mimicking a mass lesion

Figure 3

Reconstructed computerized tomography showing the pleural based pseudo-tumor

Pleural effusion in the inter-lobar fissure mimicking a tumor, which resolves with diuretic therapy is a well-known sequel of heart failure.[12] Tumor like appearance of pleural fluid in heart failure is due to transient fluid loculation in the interlobar fissures (oblique or horizontal fissure).[2] The inter-lobar pleural fluid and the tumor like appearance it produces disappear with therapy for heart failure. Pseudotumor due to pleural effusion often occur along lobar fissures and characteristically have tapering ends.[2] Though the opacity in this case was along the line of horizontal fissure, lack of tapering ends made the suspicion inconclusive in chest X-ray. Pulmonary inflammatory tumors, frequently referred as pseudotumor are benign pulmonary parenchymal mass lesions, which occur as a result of an inflammatory reaction probably due to respiratory infection.[3] Unlike the vanishing tumor of heart failure which resolves spontaneously, pulmonary inflammatory tumors need surgical excision.[3] The lack of isolation of Mycobacterium tuberculosis is a strong limitation for the causal association in our case. However, the exclusion of heart failure, malignancy, rheumatoid arthritis and systemic lupus erythematosis coupled with a markedly elevated adenosine deaminase and favorable response to anti-tuberculosis drugs makes the etiology likely to be tuberculous. The fact that isolation of tubercle bacilli is possible only in less than a third of tuberculous pleural effusion adds to our argument.[4]