Next, case examples will illustrate how knowledge of the anatomic distribution of the basic HRCT patterns helps in formulating the differential diagnosis of disease. Note how the examples of the pathologic changes, which are not taken from the same cases, correlate with the HRCT findings. After answering the questions with each illustration, you will be given a differential diagnosis and the diagnosis of the particular case.
Section 1
Look at Images 1 and 2.
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What is the major abnormality in this case? a) Linear
opacities F = mediastinal end of the right major interlobar fissure | ||||||||||
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What is the distribution of the major abnormality? a) Bronchovascular
interstitium | ||||||||||
Section 2
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Find 3 pleural nodules in the right lung. Find an example of thickened bronchovascular interstitium in the right lung. Find thickened fissural pleura with nodules along the outer portion in the left lung. Find interlobular septal nodules. F = mediastinal end of the right major interlobar fissure | ||||||||||
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Find nodules along 2 interlobular septa originating from the right fissure. Find a group of centrilobular nodules in the right lung. Outline this group of centrilobular nodules. Find a nodule at the proximal end of thickened bronchovascular interstitium in the right lung. | ||||||||||
Note the unmarked nodules along the fissural pleura bilaterally. Architectural distortion is seen here as angulation along the major fissure on the right.
Section 3: Gross Appearance
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Pleural Abnormalities The pleural surface of this lung shows multiple nodules corresponding to the pleural nodules noted in the first image above. | |||||||
Section 4: Histologic Findings
Look at the next two histologic images and answer the questions.
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What is the histologic distribution of the lesions? B = Bronchovascular bundle I = Interlobular septum | ||||||
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High magnification of a single nodule illustrated above What is the diagnosis of this lesion?
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Note: The diagnoses and features listed are not intended to be complete. See standard references.
Differential diagnosis of nodules and lines on HRCT: Diagnoses include sarcoidosis and lymphangitic tumor. Architectural distortion, as shown on image 2 is frequent in sarcoidosis, but not with lymphangitic tumor.
Histologic differential diagnosis: Infectious granulomatous disease (tuberculous or fungal), sarcoidosis, hypersensitivity pneumonia (granulomas are usually less well-formed), and reaction to tumor or drug should be considered.
Diagnosis: Sarcoidosis
Summary of diagnostic features of sarcoidosis on HRCT
See Case Study 33 for other examples of sarcoidosis.
b. The major abnormality is the presence of nodules. Also present are linear abnormalities (answer a): thickened fissures, bronchovascular interstitium, and interlobular septa.
The distribution of the nodules includes all of the regions listed although the centrilobular nodules are subtle.
Thickened bronchovascular interstitium
Nodules along interlobular septum
Nodule along interlobular septum originating from the right fissure
Nodule at proximal end of thickened bronchovascular interstitium
Thickened fissural pleura with nodules along the outer portion
The distribution of lesions is bronchovascular, interlobular septal, and pleural. Some of the bronchovascular nodules extend peripherally into the centrilobular regions. The distribution is the same as that seen in the HRCT images.
Non-necrotizing granuloma composed of epithelioid histiocytes, multinucleated giant cells, and lymphocytes
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