Radiography
Findings
Peribronchial thickening, nodularity, and septal lines in a patient with AIDS and pulmonary involvement of Kaposi sarcoma.
- Radiographic findings in diffuse KS comprise 2 major patterns: linear interstitial nodules and fluffy ill-defined nodules. Coexistence of the 2 patterns is not uncommon.
- There is a tendency toward a perihilar distribution. This reflects the bronchovascular-centric nature of the disease, with characteristic thickening along bronchovascular bundles. The thickening becomes more nodular with tumor progression, with eventual confluence of poorly marginated nodules leading to dense airspace consolidation.
- The middle and lower portions of the lungs are affected more frequently than the upper zones.
- Classically, nodules are described as flame shaped or spiculated. They typically measure 1-2 cm in diameter and frequently number more than 10.
- Septal lines may be seen as a result of lymphatic obstruction or tumor invasion (see Image above and Image 1 in Multimedia).
- The less common focal form appears as segmental, lobar, or masslike consolidation.
- Airway involvement is common, occurring in as many as 75% of patients and occasionally leading to distal atelectasis.
- Effusions are common (30-90% of patients) and may be unilateral or bilateral.
- Hilar or mediastinal lymphadenopathy is reported in 10-16% of patients, although it is rarely bulky and is often not appreciated radiographically.
Degree of Confidence
Radiographic appearances of pulmonary KS are among the most distinctive seen in patients with AIDS; even subtle abnormalities should be viewed as suggestive of pulmonary involvement in a patient with known mucocutaneous disease.
False Positives/Negatives
See Differentials.
Computed Tomography
Findings
Marked peribronchovascular thickening on high-resolution CT in a patient with AIDS and pulmonary Kaposi sarcoma (same patient as in Image 1 in Multimedia). Parenchymal nodularity and a unilateral pleural effusion are present.
Irregular thickening of interlobular septa resulting from tumor infiltration and ill-defined parenchymal micronodularity in a patient with AIDS and pulmonary Kaposi sarcoma (same patient as in Images 1-2 in Multimedia).
- In patients with KS, characteristic CT findings correlate with findings on chest radiography, with bronchial wall thickening, ill-defined nodules, and areas of consolidation in a perihilar bronchocentric distribution (see Images above and Images 2-3 in Multimedia).
- Frequently, the nodules are seen to be surrounded by a halo of ground-glass attenuation, representing localized hemorrhage.
- Interlobular septal thickening is a common feature seen on high-resolution computed tomography (HRCT).
- Pleural effusions and, less commonly, adenopathy may be identified.
- Occasionally, patients with pulmonary KS with hemoptysis may present with patchy ground-glass attenuation caused by hemorrhage.
Degree of Confidence
Among AIDS-related thoracic diseases, KS is one of the most reliable diagnoses made on the basis of imaging findings. An accurate diagnosis of pulmonary KS can be established by CT scans in 90% of patients.15,16,17
False Positives/Negatives
See Differentials.
Magnetic Resonance Imaging
Findings
There is little evidence that MRI is as useful as other methods in diagnosing pulmonary KS. Although MRI is an excellent modality for detection of thoracic wall involvement, it is not useful in intrathoracic lesions apart from, perhaps, imaging large-vessel involvement.18
- In a series of 10 patients with AIDS-related KS, T1-weighted spin-echo images showed focally increased signal intensity in the pulmonary parenchyma.
- Enhancement was observed in parenchymal lesions and along the bronchovascular bundles after the intravenous administration of a gadolinium-based contrast agent. Gadolinium-based contrast agents (gadopentetate dimeglumine [Magnevist], gadobenate dimeglumine [MultiHance], gadodiamide [Omniscan], gadoversetamide [OptiMARK], gadoteridol [ProHance]) have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). For more information, see the eMedicine topic Nephrogenic Fibrosing Dermopathy. The disease has occurred in patients with moderate to end-stage renal disease after being given a gadolinium-based contrast agent to enhance MRI or MRA scans.NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness. For more information, see the FDA Public Health Advisory or Medscape.
- The second echo of T2-weighted spin-echo images resulted in markedly reduced signal intensity in affected areas.
- The findings were not observed in a control group of patients with AIDS-related PCP.
- The signal intensity of KS lesions has been postulated to be related to the angiomatous and fibrous components of the tumor.
Ultrasonography
Findings
Ultrasonography of the thorax is useful in the evaluation of pleural disease and for guiding therapeutic thoracentesis.
Nuclear Imaging
Findings
Approximately two thirds of patients with KS presenting with new pulmonary abnormalities have coexistent opportunistic infections. Differentiating KS from opportunistic infections is not always possible by using anatomic imaging.
Gallium-67/thallium-201 (67 Ga/201 Tl) radionuclide imaging has been used to distinguish AIDS-related KS from other pulmonary disease processes. KS is201 Tl avid, but it does not take up67 Ga. Abnormal chest radiographic findings in association with negative67 Ga findings suggest the presence of pulmonary KS.
Indium-111–labeled polyclonal immunoglobulin is taken up by infection but not by KS or lymphoma. Indium-labeled liposomes have been shown to accumulate in KS, but uptake has also been reported with lymphoma.19
Degree of Confidence
Radionuclide scans are a useful adjunct to radiographs and CT scans, particularly when radiographic findings are complex and when the exclusion of opportunistic infections that complicate KS is important. Indium-11-labeled polyclonal immunoglobulin uptake has a sensitivity of 97% in the diagnosis of AIDS-related pulmonary infections; by contrast, chest radiography has a sensitivity of 62%. Although high-resolution computed tomography (HRCT) is superior to chest radiography, some have suggested that HRCT may be less sensitive than67 Ga scintigraphy in the assessment of suspected Pneumocystis jiroveci pneumonia(PCP).
False Positives/Negatives
A false-positive rate of 15% has been reported with gallium scanning in the assessment for Pneumocystis jiroveci pneumonia (PCP). Other infections and lymphomas may also take up gallium. It has been suggested that thallium uptake may occur in lymphoma and infections such as PCP.
More on Kaposi Sarcoma, Thoracic |
| Overview: Kaposi Sarcoma, Thoracic |
 Imaging: Kaposi Sarcoma, Thoracic |
| Follow-up: Kaposi Sarcoma, Thoracic |
| Multimedia: Kaposi Sarcoma, Thoracic |
| References |
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References
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Further Reading
Keywords
KS, Kaposi's sarcoma, thoracic Kaposi's sarcoma, acquired immunodeficiency syndrome, AIDS, human immunodeficiency virus, HIV, human herpesvirus 8, HHV-8, Kaposi sarcoma herpesvirus, KSHV
