Case 19

Section 1

Look at images 1, 2, and 3 from progressively lower slices through the thorax.

Image 1

What is the abnormality?



What is the distribution?



Image 2

Image 3

Find a cluster of centrilobular nodules with central lucencies in the right lung.


Section 2

Image 1

Find a cluster of centrilobular, ground-glass nodules in the right lung.

Find a cluster of centrilobular, consolidated nodules in the left lung.

Section 3

Gross Features

This lung was firmer than normal and had a gritty sensation when it was cut with a knife. Centrilobular markings are accentuated. The fine, white, branching, linear structures correspond to airways. Together with the fuzzy whitish regions around them, they comprise the centrilobular nodules seen on HRCT. These markings are more prominent in the upper, than in the lower, lung.

Find 2 representative lobules.


Section 4

Special Stain of Centrilobular Area

A stain for phosphate (black) shows deposition in the wall of an airway and in the basement membrane and elastic tissues of the alveolar walls, which are slightly thickened. Alveolar walls farther from the centrilobular region were not stained.

Find the stained airway wall. The lumenal contents include epithelial cells that were sloughed postmortem.


Special Stain of Alveolar Walls

At higher magnification, staining of the linear basement membrane and staining of coiled elastic fibers centrally in the alveolar walls can be seen.

Find 2 examples of staining of coiled, central elastic fibers.


Differential diagnosis of peribronchial/peribronchiolar nodular densities on HRCT: Metastatic calcification, endobronchial spread of infection (e.g., tuberculosis), hypersensitivity pneumonia, sarcoidosis, silicosis, Langerhans' cell histiocytosis, respiratory bronchiolitis.

Histologic differential diagnosis: Metastatic calcification in normal lung tissue and dystrophic calcification in previously inflamed foci in the lung. The latter may be focal and in the upper or lower lung. The histologic stain used here stains phosphate black. An alizarin stain will color calcium red.

Diagnosis: Metastatic calcification related to renal failure (see bone scan below)

Diagnostic features of metastatic calcification on HRCT

Comment: Metastatic calcification refers to deposits of calcium salts in normal tissues. It may occur in persons with high serum calcium of any cause or in those with an elevated calcium x phosphate product, as in the present case. Deposits favor sites of high pH, including the upper lung zones.


Bone Scan for Lung Calcification

Although metastatic calcification sometimes produces calcific densities visible on soft tissue windows, the calcification is often below the resolution of HRCT, as in this case. In order to confirm a diagnosis of metastatic calcification in this patient with chronic renal failure and to exclude a chronic infection, such as tuberculosis, a bone scan was performed to identify calcium in the lung.

The bone scan agent is a phosphate analogue that binds to calcium. This frontal image from the bone scan shows uptake (black) of the agent in the skeletal system (skull, shoulders, ribs, sternum, pelvis, and extremities). The lungs also show diffuse uptake, with the heart silhouetted as a white structure. The lung uptake of the bone scan agent confirms the diagnosis of metastatic calcification. (Bone scans do not show uptake in calcified tuberculous granulomas because the absence of blood supply to the walled-off granuloma does not permit access of the agent to the calcium).




Table of Contents





























Representative lobule






























Airway wall






























Staining of coiled elastic fibers in alveolar wall



























Peribronchial, peribronchiolar, and centrilobular ground-glass or consolidated nodular opacities of various sizes. Lumens tend to be spared.

































Lesions are present diffusely in both lungs but tend to spare the subpleural regions. There is a distinct upper lung predominance.





























Cluster of centrilobular, ground-glass nodules




























Cluster of centrilobular, consolidated nodules




























Cluster of centrilobular nodules with central lucencies