Imaging in Oncology
Imaging in Oncology (Answer)
Answer:
3. mycotic pulmonary artery aneurysm
The predischarge CT image of this immunocompromised patient demonstrates findings
consistent with invasive pulmonary aspergillosis with nonenhancing peripheral wedge-shaped
and nodular central opacities. Follow-up CT scans demonstrate a decrease in the size of
the previously noted opacities with a new, more central nodular opacity. This central
lesion demonstrates dense contrast opacification, measures approximately 3 cc, and
occupies the location of a previously seen normal caliber blood vessel. The location,
coupled with the contrast enhancement, is highly suggestive of a vascular lesion. In light
of the patient's clinical history, these findings indicate a diagnosis of mycotic
pulmonary artery aneurysm as the best choice among the options provided.
Discussion
Aspergillus sp. in the immunocompetent host rarely produce clinically
significant sequelae. These organisms, however, frequently become pathogenic in patients
who are immunocompromised. The most frequent site of infection is the lung.1
Progression to invasive pulmonary aspergillosis may rise to as high as 11% in high-risk,
immunocompromised patients.2
An ominous complication of invasive pulmonary aspergillosis is the development of a
mycotic aneurysm involving a pulmonary artery. The potential for rapid growth (Fig 2) and
rupture necessitates prompt recognition and treatment.3 The pathogenic
mechanisms for the development of a mycotic aneurysm include embolism of the vasa vasorum,
lodging of septic emboli within the vessel followed by invasion of the intima, and
extension to an erosion of the vessel wall from an adjacent lung infection either directly
or via the lymphatics.4
Radiographically, a mycotic aneurysm of the pulmonary artery may be difficult to
differentiate from inflammatory or neoplastic lesions of the lung.3 An aneurysm
located near the hilum may appear similar to mediastinal lymphadenopathy due to a variety
of etiologies (eg, tuberculosis, sarcoid, or lymphoma). Peripherally located aneurysmal
lesions may simulate any of the numerous etiologies of a pulmonary lesion (eg, metastatic
disease or primary lung neoplasm).3 Features that suggest an aneurysm include a
rapid change in contour of the vessel,3 enhancement of the lesion during the
arterial phase of contrast injection with slow wash-out that is secondary to loss of
elastic tissue,5 pulsation during fluoroscopy (Pezzi's sign or "hilar
dance"),6 and a triangular cardiac shadow on the chest radiograph due to
rotation of the heart secondary to displacement by the dilated pulmonary artery (Shadow of
Laubry and Bordet).6
Given the potentially grave consequences of this disease complication, early
recognition and definitive treatment are imperative. In the immunocompromised patient with
a history of pulmonary aspergillosis and a new pulmonary lesion, clinical suspicion for
mycotic aneurysm is high. CT of the thorax with contrast enhancement is helpful in
narrowing the differential diagnosis but may fail to elucidate the vascular nature of a
lesion.7 If the diagnosis is still questionable and the patient is a suitable
candidate, pulmonary angiography is indicated as a more definitive diagnostic procedure to
differentiate a mycotic aneurysm from other vascular and nonvascular pulmonary lesions.3
Biopsy of a lesion in a patient whose clinical presentation supports a differential
diagnosis that includes a mycotic aneurysm is, for obvious reasons, contraindicated.
Due to the high rate of rupture, treatment of a mycotic aneurysm of the pulmonary
artery is recommended, even if the patient is asymptomatic. Treatment options include, but
are not limited to, surgical resection, aneurysmorrhaphy, lobectomy, or banding.8
For more peripheral lesions, embolotherapy using particles or balloons can be used.9
In this case, right pneumonectomy was required due to aneurysmal involvement of the second
division of the right pulmonary artery, thus involving essentially all lobes of the lung.
References
- Amaissie E. Opportunistic mycoses in the immunocompromised host: experience at a cancer
center and review. Clin Infect Dis. 1992;14:543-553.
- Boon AP, O'Brien D, Adams DH. 10-year review of invasive aspergillosis detected at
necropsy. J Clin Pathol. 1991;44:452-454.
- Jaffe RB, Condon UR. Mycotic aneurysms of the pulmonary artery and aorta. Radiology.
1975;116:291-298.
- Libshitz HI, Pagani JJ. Aspergillosis and mucormycosis: two types of opportunistic
fungal pneumonia. Radiology. 1981;190:301 306.
- Monichik J, Wilkens EW Jr. Solitary aneurysm of the middle lobe artery: a case report
and review of solitary peripheral pulmonary artery aneurysms. Ann Thorac Surg.
1974;17:496-503.
- Deterling RA Jr, Clagett OP. Aneurysm of the pulmonary artery: review of the literature
and report of a case. Am Heart J. 1947;34:471-499.
- Chung CW, Doherty JU, Kotler R, et al. Pulmonary artery aneurysm presenting as a lung
mass. Chest. 1995;108:1164-1166.
- Bartter T, Irwin RS, Nash G. Aneurysm of the pulmonary arteries. Chest. 1988;94:
1065-1075.
- Renie WA, Rodeheffer RJ, Mitchell S, et al. Balloon embolization of a mycotic pulmonary
artery aneurysm. Am Rev Respir Dis. 1982;126:1107-1110.
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