Localized Amyloid 'tumours' of the Lung Simulating Malignant Neoplasms.

Amyloidosis has been classified by Symmers (1956) into (1) generalized secondary amyloidosis; (2) generalized primary amyloidosis ; and (3) localized amyloidosis. Involvement of the respiratory tract by amyloid material in the generalized systemic form of the disorder is not as rare as is commonly supposed. In amyloidosis associated with a recognized predisposing disease the incidence is at least 10% (Dahlin, 1949), and in generalized primary amyloidosis in the absence of any recognized predisposing disease Symmers (1956) found involvement of the lungs in 30% of 145 cases. In both these groups of cases, which form the majority of all patients with amyloidosis, pulmonary symptoms are usually overshadowed by the severity of changes in other organs, notably the kidneys, spleen, and liver in the secondary disease, and the heart, alimentary tract, liver, spleen, and kidneys in primary amyloidosis. Occasionally, however, diffuse pulmonary involvement, particularly in secondary amyloidosis, may be the dominant clinical feature with death occurring from respiratory insufficiency. A further, but relatively rare, type of amyloidosis is localized to one organ or anatomical site; diffuse disease does not develop and there is no known predisposing condition. The commonest sites where such lesions have been reported as occurring are the skin and mucous membranes (mouth, vagina, and conjunctiva), the urinary bladder and urethra, the upper respiratory tract, particularly the larynx, and the lower respiratory tract including lesions of the trachea, bronchi, and lung parenchyma. In the lower respiratory tract, solitary or multiple tumorous masses may form, often with symptoms due to obstruction of the air passages and clinical and radiological appearances which are readily mistaken for primary or secondary neoplasms of the lung. In a review of localized amyloidosis of the lower respiratory tract, Prowse (1958) was able to find only 16 cases reported in the literature to which he added two that he had personally observed. From the diagnostic and prognostic viewpoints he emphasized the importance of subdividing these cases into the following three groups according to the distribution of the lesions: group 1, multiple nodules of amyloid material confined to the peripheral lung parenchyma; group 2, a solitary tumorous mass of amyloid material affecting a major bronchus; and group 3, amyloid localized to the lower respiratory tract but of a more widespread distribution, involving the mucosa and submucosa of many of the major air passages; this group he calls diffuse tracheo-bronchial amyloidosis. Although cases in all these groups can simulate lung neoplasms, it is in those of groups 1 and 2 that the presence of localized masses visible radiologically is most likely to cause diagnostic confusion. This paper reports two cases, one in group 1 and one in group 2, in both of which the diagnosis of a neoplasm, in one case multiple metastases and in the other adenoma or carcinoma of the bronchus, seemed from the clinical and radiological viewpoints almost certain. These cases are reported in order to increase awareness of these unusual manifestations of a disease that appears to show an actual increase in incidence.