Nodular senile pulmonary amyloidosis: a unique case confirmed by immunohistochemistry, mass spectrometry, and genetic study
Nodular pulmonary amyloidosis, characterized by solitary or multiple parenchymal nodules, is primarily composed of amyloid immunoglobulin light chain protein. Pulmonary involvement by senile amyloidosis has been reported as an incidental finding with scattered or diffuse interstitial deposition of amyloid protein transthyretin mostly in patients with cardiac senile amyloidosis in a small number of autopsy cases. We report a unique case of pulmonary senile amyloidosis presenting with conglomerated nodular deposition of amyloid protein transthyretin as the main clinical manifestation. The patient was an 82-year-old man who presented with recurrent pleural effusions and nodular replacement of pulmonary parenchyma on a chest computed tomographic scan. He underwent a wedge resection of the lesion. Histologic examination revealed a massive deposition of Congo red-positive amyloid identified as amyloid protein transthyretin by both immunohistochemistry and mass spectrometry using formalin-fixed, paraffin-embedded tissues. Molecular testing did not show any mutation associated with familial amyloidosis in the TTR gene, further supporting the diagnosis of senile amyloidosis. To our knowledge, this is the first documented case of nodular senile amyloidosis of the lung that was confirmed with the current state-of-the-art methods.