The benign pulmonary nodules - so it's not cancer, what could be?

We report a case of a 71-year-old woman with a history of bronchiectasis and Sjogren's syndrome who reported anorexia, weight loss, and a productive cough.

The X-ray revealed multiple nodular opacities of varying dimensions scattered throughout the lung fields, with irregular margins and random distribution (Figure 1). A subsequent computed tomography (CT) was then performed for further evaluation, which also showed the presence of mediastinal adenomegalies and confirmed the ill-defined nodular densities occupying both lungs with variable sizes. There were no observed calcification or cavitation lesions (Figure 2). PET-CT showed an increase in FDG uptake in the pulmonary lesions (Figure 3). Resection of the pulmonary nodule was performed by thoracotomy and the material was sent for pathological anatomy demonstrating the presence of amyloidosis (Figures 4 and 5). Research on amyloid substance on abdominal wall biopsy was negative, so we concluded that this is a case of localized amyloidosis in the lung. The patient remained asymptomatic and under surveillance. After two years of follow-up, the lesions are stable.

Amyloidosis is a disease of protein metabolism with extracellular deposition of the amyloid substance in different organs and tissues [1].

The overall incidence of amyloidosis is about ten cases per million per year, estimated if the incidence of pulmonary amyloidosis reaches about 20% [2].

Pulmonary involvement is rare and can occur in isolation or in association with systemic disease. Three patterns of pulmonary amyloidosis are described: nodular pulmonary amyloidosis, tracheobronchial/laryngeal amyloidosis, and diffuse/septal-alveolar parenchymal amyloidosis [3,4].

Nodular pulmonary amyloidosis is a rare, benign, and indolent disease. It has a variable presentation and imaging studies show nonspecific findings that can simulate other more common pathologies such as neoplasms. Localized forms of amyloidosis progress slowly and rarely require treatment, unlike systemic amyloidosis forms [1,3].

PET-CT, performed in the differential diagnosis of neoplasms, shows that amyloid deposits have high activity, like other metabolically active lesions, and should therefore be carefully interpreted. F-FDG is recognized for being absorbed by not only cells engaged in inflammation and infection (leukocytes), but also by cells participating in the clearance response, such as macrophages, monocytes, and giant cells. In cases of localized AL amyloidosis, the presence of giant cells is believed to be attributed to their involvement in amyloid production [5].

This case emphasizes how crucial it is for the radiologist to be familiar with pulmonary amyloidosis, allowing for a prompt clinical approach with the optimization of its final diagnosis.