Radiology/Pathology Correlation

Unknown 6


A 75-year-old woman had a long history of constipation and progressive shortness of breath.

Figure 1. Chest Radiograph

Describe the abnormality. Is there lymphadenopathy? Pleural effusion?


Figure 2. HRCT

Describe the changes on the HRCT.




What is the differential diagnosis?





Figure 3

Gross Appearance

This slice of lung from another patient shows irregularly shaped consolidated masses on both sides of the interlobar fissure at the base. Note the distortion of the fissure. Surrounding lung parenchyma is also firm and shows fine honeycombing.

Outline the consolidated mass that crosses the fissure. Click on the structure in the image to get verification.

Outline the surrounding area of honeycombing in the upper lobe.


Figure 4

Histologic Findings

Here, two bronchioles are filled with vacuolated macrophages. The adjacent parenchyma shows fibrosis, some apparently empty, rounded spaces of different sizes, and scattered chronic inflammatory cells.

Find the two bronchioles.

Find the largest space in the surrounding connective tissue.




Figure 4a. High-power View of Figure 4

Some of the large spaces in the fibrotic interstitium have multinucleated giant cells adjacent to them.

Find a multinucleated giant cell.



Figure 5

Here, an air space contains many vacuolated macrophages, as does the interstitium, which is covered by reactive type II cells.

Find reactive type II cells of the alveolar wall.

What is the differential diagnosis?



Scroll down after answering the questions.
























Discussion: Lipoid accumulations within the lung may have endogenous or exogenous sources [1]. Exogenous lipoid pneumonias often occur as repeated, subclinical aspiration events in patients using mineral oil as a laxative, or in patients with structural esophageal disease or neurological disease, both of which predispose to aspiration. Lipoid pneumonias also occur in infants with feeding difficulties [2]. Rarely, occupational inhalation of aerosols of oily substances occurs [3]. The patient may be asymptomatic or have symptoms of cough and dyspnea [3].

Radiographic findings: In most cases, the initial radiographic manifestation of lipoid pneumonia is primarily air space consolidation. The distribution is commonly dependent, affecting the lower lobes. Because the aspiration leading to the development of lipoid pneumonia may occur while the patient is sleeping, the superior segments of the lower lobes and the posterior segments of the upper lobes may be affected. The consolidation may be poorly-defined or well-defined, and small acinar nodules are not uncommon early in the disease. Later, as the lipid is absorbed into the pulmonary interstitium, a linear and reticular pattern may develop [3-6].

Occasionally, a peripheral, mass-like consolidation may be encountered (the so-called "paraffinoma")[3-7]. Such opacities may be associated with linear opacities, reflecting interlobular septal thickening. Calcification and cavitation (sometimes related to secondary infection) are rare occurrences in patients with lipoid pneumonia [7,8].

HRCT findings: In the mass-like consolidations, HRCT may allow a definitive diagnosis of lipoid pneumonia if fat is identified within the pulmonary opacities (figures 6 and 6a). Fat may be identified on HRCT by its noticeably lower attenuation than surrounding soft tissue, or the density of the tissue in question may be measured directly on the CT scanner. Fat usually measures less than -80 Hounsfield units. Fat may also be identified on MR imaging of the chest: fat will show increased T1 signal, or may be specifically identified using chemical shift imaging.


Figure 6. Localized Mass--Soft Tissue Window

Another patient with lipoid pneumonia had this spiculated mass shown below as the lung window. It shows a central area of low attenuation consistent with fat.

Outline the area of low attenuation.

Figure 6a. Localized Mass--Lung Window

Mass-like lesions in patients with lipoid pneumonia may be quite spiculated, and may be associated with surrounding architectural distortion, indicating the presence of fibrosis. Shrinkage of parenchyma posterior to this lesion is accompanied by overinflation anteriorly (top). This picture illustrates findings similar to those in the slice of gross lung (figure 3) shown above.

In patients with lipoid pneumonia in whom "fat" cannot be identified, the pneumonia typically presents as widespread ground-glass opacity associated with interlobular septal thickening (figure 2). While the combination of ground-glass opacity and interlobular septal thickening suggests the presence of "crazy paving" and pulmonary alveolar lipoproteinosis, the sharp demarcation between normal and abnormal lung that characterizes alveolar lipoproteinosis is usually not observed with lipoid pneumonias [9].

Pathology: Histologically, exogenous lipoid material is taken up by macrophages, which then fill alveolar spaces and move into the interstitium. Some of the lipoid material reaches regional or other lymph nodes and sometimes even other organs. Over time fibrosis results, expanding the centrilobular interstitium, interlobular septa and even alveolar walls. Type II cells become hyperplastic. Within the interstitium there may be a granulomatous response with multinucleated giant cells and a variable amount of chronic inflammation. Also, as macrophages die, lipoid droplets can coalesce in the interstitium to form large globules, often surrounded by multinucleated giant cells (figures 4 & 4a above) [1].

Therapy and Complications: Treatment consists of discontinuing use of the lipoid material or taking measures to prevent aspiration [3]. Localized masses can be resected, if necessary. Pneumonic infiltrates have been treated with some success with corticosteroids or whole lung lavage [1,10]. Secondary infection with non-tuberculous mycobacteria or fungi has been reported [8].

Diagnosis: Identification of "fat" by imaging studies, obtaining a history of use of, or exposure to, oily products, and finding lipoid-filled macrophages in respiratory secretions or transbronchial or needle biopsies make a strong case for the diagnosis and may obviate the need for larger biopsies or resection.

Comments on the Radiographic Features

Chest radiographs usually show one of two patterns:

Comparable HRCTs show

Comments on the Pathologic Features

Final Diagnosis: Exogenous lipoid pneumonia

References: To return to reference section after viewing abstract, click here before clicking on "abstract".

1. Spickard III A, Hirschmann J. Exogenous lipoid pneumonia. Arch Intern Med 1994; 154:686-692. Abstract

2. Collins K, Geisinger K, Wagner P, Blackburn K, Washburn L, Block S. The cytologic evaluation of lipid-laden alveolar macrophages as an indicator of aspiration pneumonia in young children. Arch Pathol Lab Med 1995; 119:229-231. Abstract

3. Gondouin A, Manzoni Ph, Ranfaing E, Brun J, Cadranel J, Sadoun D, Cordier J, Depierre A, Dalphin J. Exogenous lipid pneumonia: a retrospective multicentre study of 44 cases in France. Eur Respir J. 1996; 9:1463-1469. Abstract

4. Kennedy J, Costello P, Balikian J, Herman P. Exogenous lipoid pneumonia. AJR Am J Roentgenol 1981; 136:1145-1149.

5. Lee K, Müller N, Hale V, Newell Jr J, Lynch D, Im J-G. Lipoid pneumonia: CT findings. J Comput Assist Tomogr 1995;19:48-51. Abstract

6. Laurent F, Philippe J, Vergier B, Granger-Veron B, Darpeix B, Vergeret J, Blanc P, Velly J. Exogenous lipoid pneumonia: HRCT, MR, and pathologic findings. Eur Radiol 1999; 9:1190-1196. Abstract

7. Case Records of the Massachusetts General Hospital. N Engl J Med 1999; 341:1379-1385.

8. Jouannic I, Desrues B, Léna H, Quinquenel M, Donnio P, Delaval Ph. Exogenous lipoid pneumonia complicated by Mycobacterium fortuitum and Aspergillus fumigatus infections. Eur Respir J 1996; 9:172-174. Abstract

9. Franquet T, Giménez A, Bordes R, Rodríquez-Arias J, Castella J. The crazy-paving pattern in exogenous lipoid pneumonia: CT-pathologic correlation. AJR Am J Roentgenol 1998; 170:315-317. Abstract

10. Wong C, Wilsher M. Treatment of exogenous lipoid pneumonia by whole lung lavage. Aust NZ J Med 1994:24:734-735.

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Last modified 9/12/02


























The frontal view of the chest shows diffuse, bilateral symmetric opacities without evidence of lymphadenopathy or pleural effusion. Additionally, there is no evidence of mediastinal widening or cardiomegaly.





























High-resolution CT of the lung shows bilateral, poorly-defined areas of ground-glass opacity associated with interlobular septal thickening and intralobular fibrosis.


























Radiographic differential diagnosis: The differential diagnosis includes numerous causes of air space filling processes, particularly hydrostatic pulmonary edema, pulmonary hemorrhage, diffuse opportunistic infection (especially pneumocystis pneumonia), pulmonary alveolar proteinosis, desquamative interstitial pneumonia, lipoid pneumonia, acute hypersensitivity pneumonitis, and other causes of acute lung injury.





























Mass lesion that crosses fissure






























Honeycombed scar surrounding mass
























































































Multinucleated giant cell



























The histologic differential diagnosis includes exogenous lipoid pneumonia and endogenous lipoid pneumonia. The diagnosis is exogenous lipoid pneumonia because the cytoplasmic vacuoles are large compared to the small vacuoles of endogenous lipoid pneumonia. Also characteristic of the exogenous type, some of the lipoid material is extracellular with a giant cell reaction (Figures 4 & 4a).

What special stain would help with the diagnosis? Answer
































Type II cells































Low attenuation consistent with fat