Nodular pulmonary amyloidosis
Nodular pulmonary amyloidosis is a subtype of pulmonary amyloidosis. It is considered a limited form of amyloidosis characterized by one or more intrapulmonary nodules or masses (amyloidomas).
Patients are usually asymptomatic. Some may rarely present with a cough or shortness of breath.
Albeit rare in general it is commoner than the diffuse parenchymal form. The incidence is thought to peak around the 6th decade of life 5.
There is nodular deposition of amyloid within the lungs. Amyloid is an inert, proteinaceous, homogeneous, acellular, and eosinophilic material.
When subjected to histochemical staining with Congo red shows green birefringence under polarized light.
Nodular amyloid deposits usually appear in multiple sites; focal deposits are much less common.
Amyloid nodules usually tend to be localised to the lower lobes and towards the peripheral and subpleural areas
Four characteristic features have been described on CT 1,4-5:
- sharp, smooth and lobulated contours
- often central or in an irregular pattern within the nodule
- seen in ~50% of cases
- variable shapes and sizes: 0.5-15 cm
- slow growth: often over years and with no regression
Associated cavitation has been described but is very rare.
Vary rarely, lung cysts can also form (most often described with localised amyloidosis in association with Sjögren syndrome) 3,6,8.
Treatment and prognosis
Management options are dependent on the severity of symptoms where asymptomatic patients usually do not require treatment. In some situations they are resected which can be both diagnostic and curative 5.
Nodular pulmonary amyloidosis is a great mimicker of various entities which include
- primary or metastatic malignant nodules
- granulomatous disease
- silicosis 2
- multiple pulmonary hamartomas 2
For a broader differential consider
A tissue biopsy is considered essential for a definitive diagnosis.
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- 4. Vieira IG, Marchiori E, Zanetti G et-al. Pulmonary amyloidosis with calcified nodules and masses - a six-year computed tomography follow-up: a case report. Cases J. 2009;2 (1): 6540. doi:10.4076/1757-1626-2-6540 - Free text at pubmed - Pubmed citation
- 5. Giménez A, Franquet T, Prats R et-al. Unusual primary lung tumors: a radiologic-pathologic overview. Radiographics. 2002;22 (3): 601-19. Radiographics (full text) - Pubmed citation
- 6. Chew KM, Clarke MJ, Dubey N et-al. Nodular pulmonary amyloidosis with unusual, widespread lung cysts. Singapore Med J. 2013;54 (5): e97-9. Pubmed citation
- 7. Webb WR, Muller NL, Naidich DP. High-resolution CT of the lung. Lippincott Williams & Wilkins. ISBN:0781769094. Read it at Google Books - Find it at Amazon
- 8. Seaman DM, Meyer CA, Gilman MD, McCormack FX. Diffuse cystic lung disease at high-resolution CT. AJR. American journal of roentgenology. 196 (6): 1305-11. doi:10.2214/AJR.10.4420 - Pubmed