Case 15

Section 1

Look at images 1 and 2.

Image 1


What are the abnormalities?



lgg1lgg2consolImage 2

Find a region of normal lung and give its boundaries.


Outline 2 areas of septal lines coexisting with ground-glass opacity in each image.

In image 1 find abnormal lung where septal lines are not visible.


Section 2: Definition


A pattern of coexistent septal lines and ground-glass that is sharply demarcated from normal lung is known as "crazy-paving."

Section 3

Histologic Findings

This section shows portions of 3 lobules separated by interlobular septa (arrows). The alveolar spaces of the lobules at the top and bottom are filled with pink material. Similar material widens the interlobular septa. The central lobule is normal, although it is collapsed.

On HRCT, the lobules at the top and bottom and the interlobular septa correspond to ground-glass opacity and septal lines, respectively.

Combined with the normal lung, this pattern represents "crazy-paving."


Medium-(left) and High-(right) Power Views of the Alveolar Exudate

Left panel: Dark pink clumps and empty clefts mar the homogeneous appearance of this material. Alveolar walls show minimal to mild thickening without type II cell hyperplasia.

Right Panel

A few macrophages are degenerating within the exudate, which has a granular appearance.

Find 2 degenerating macrophages.

Find 2 cholesterol clefts (cholesterol crystals have been dissolved in processing).


Electron microscopic images of the alveolar exudate would show surfactant material.

Differential diagnosis of "crazy-paving" on HRCT: The differential diagnosis of septal thickening and ground-glass opacity is extensive. When the pattern of "crazy-paving" is present, alveolar proteinosis is most likely but lipoid pneumonia, bronchioloalveolar carcinoma, and pneumocystis pneumonia should also be considered.

Histologic differential diagnosis: Pink material filling alveolar spaces suggests protein-rich edema fluid (if exudate is homogeneous), Pneumocystis carinii pneumonia (if exudate is foamy), alveolar proteinosis (if exudate is granular), or a mucinous exudate from adenocarcinoma (especially bronchioloalveolar carcinoma) (if exudate is homogeneous).

Diagnosis: Pulmonary alveolar proteinosis

Diagnostic features of alveolar proteinosis on HRCT



Table of Contents


































Ground-glass opacity, septal lines, and consolidation

































Septal lines coexisting with ground-glass opacity





























Abnormal lung where septal lines are not visible. This area represents consolidation: septal lines are not visible.






























Find a region of normal lung and give its boundaries.

In this image, the right middle lobe is spared along with a portion of the anterior-medial lower lobe. The latter is demarcated by interlobular septa. This sharp demarcation of normal and abnormal is very characteristic of this lesion.






























Degenerating alveolar macrophage
































Cholesterol cleft