Summary A 2-year-old captive-born male moustached tamarin was subjected to necropsy examination after a fatal head trauma. A solitary, circumscribed, subpleural mass (0.6 cm diameter) was found in the right caudal lung lobe. The mass was diagnosed as a mucinous cystadenoma. Histochemical and immunohistochemical tests were performed to further characterize the tumour. Surfactant proteins A, B, C and D were not found in the neoplastic cells, suggesting that the tumour arose from a non-surfactant producing alveolar lining cell. Pulmonary mucinous cystadenomas are uncommon benign tumours in man and have not been reported previously in animals.

Pulmonary alveolar proteinosis (PAP) is a rare human disease characterized by accumulation of surfactant in alveoli without generating an inflammatory response. Lung lesions resembling PAP were observed in seven adult tamarins (five males and two females). Gross lesions were characterized by areas of discoloration, slight bulging over the lung parenchyma, and occasional consolidation. Histological examination of tamarin lung samples revealed intra-alveolar accumulation of an amorphous, amphophilic, PAS-positive, finely granular to dense material. In some cases type II pneumocyte hypertrophy and hyperplasia with pleural and septal thickening and fibrosis were observed. Large numbers of intra-alveolar foamy macrophages were noted surrounding and/or in the vicinity of the lesions. Immunohistochemical analysis of the lung lesions using polyclonal (surfactant proteins A, B, and C) and monoclonal (surfactant protein D) antibodies revealed the granular material to be composed largely of surfactant protein B, followed by surfactant protein A. Surfactant proteins C and D (SP-D) were present in lesser quantities; with SP-D observed surrounding the lipoproteinaceous deposits. Transmission electron microscopy of the affected lungs showed numerous, irregularly-shaped, osmiophilic lamellar bodies in type II pneumocytes. The cytoplasm in alveolar macrophages was expanded, containing ingested surfactant with swollen mitochondria and rough endoplasmic reticulum. Thoracic radiographs, available in one animal, depicted the lesions as small multifocal opacities randomly distributed in cranial and diaphragmatic lung lobes. This is, to our knowledge, the first report of spontaneous PAP in nonhuman primates.