Pulmonary lymphoma
An 8yr old outdoor domestic shorthair cat with a history of chronic respiratory distress and anorexia. Radiographs/necropsy revealed a diffuse miliary interstitial lung pattern (Fig 1). Post-mortem samples of lung, liver and kidney were examined histopathologically.





Final Diagnosis
Pulmonary lymphoma
Discussion
This is a large-cell, T-cell lymphoma. It is not entirely clear whether this represents primary or metastatic lymphoma in this lung. Given the apparent random distribution of the neoplastic infiltrate, I would not exclude metastatic disease. However, as no other primary lesions were observed/reported at the time of post-mortem and no neoplasia was evident in the submitted renal or liver samples, primary pulmonary lymphoma was considered a valid differential in this case.
Pulmonary involvement with lymphoma is very uncommon in cats but should be considered amongst the potential differentials for infiltrative miliary or consolidated lung lesions. Other clinical differentials worth considering would include other metastatic neoplasia, pulmonary infiltrates with eosinophils (PIE) and granulomatous or pyogranulomatous diseases (e.g. parasitic, fungal or mycobacterial).
Refs: J Feline Med Surg. 2011 Oct;13(10):772-5 and Vet Radiol Ultrasound. 2010 Jul-Aug;51(4):386-90).