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Radiologic-Pathologic Conferences of the Massachusetts General Hospital |
1 All authors: Department of Radiology, Massachusetts General Hospital, 55 Fruit St., FND Bldg. 2, Boston, MA 02114.
Received May 6, 2006; accepted after revision August 18, 2006.
Address correspondence to R. R. Colen
(rrcolen{at}partners.org).
Keywords: chest • correlation • infectious diseases • lung diseases • radiologic-pathologic
An 89-year-old man with a history of chronic obstructive pulmonary disease (COPD) and a 30-year smoking history presented with shortness of breath and productive cough of a few months' duration. He denied any history of malignancy or recent travel. He was HIV negative and without history of organ or bone transplantation, immunodeficiency disorder, or immunosuppressive medications. On physical examination, he was found to be afebrile.
A standard chest radiograph showed an opacity in the basilar segments of the left lower lobe (Figs. 1A and 1B). Partial collapse of the right middle lobe was also incidentally noted. A chest CT scan revealed a large oval, irregular, and ill-defined mass in the left lower lobe abutting the pleura (Fig. 1C). There was no evidence of lymphadenopathy or pleural effusion. Because of the likelihood of lung carcinoma, the patient underwent a CT-guided percutaneous transthoracic left lower lobe biopsy.
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Pulmonary cryptococcosis is caused by inhalation of cryptococcal particles of the infecting organism C. neoformans variant gattii or variant neoformans. C. neoformans variant neoformans is an encapsulated, unimorphic fungus that is ubiquitous in soil and particularly abundant in pigeon excreta and decayed wood [2-4]. The neoformans variant tends to cause extensive pulmonary involvement associated with disseminated disease, especially in immunocompromised patients [2]. Cryptococcus variant neoformans and Cryptococcus variant gattii occur mainly in tropical and subtropical regions, thought to be due to its association with the Eucalyptus tree, and tend to cause more focal pulmonary and cerebral disease, mainly in immunocompetent patients [2].
Cryptococcus usually causes a confined, localized granulomatous reaction in the lung of the immunocompetent patient. However, it may result in severe, disseminated disease in immunocompromised patients [4].
The imaging manifestations of cryptococcal pneumonia include pulmonary nodules or masses, segmental or lobar consolidation, or reticulonodular opacities, the latter most commonly seen in AIDS patients. These are usually bilateral and asymmetric with measurements ranging from 5 mm to 5 cm. Distribution is predominantly peripheral and lower lobe in 80% and 58% of patients, respectively [2]. Cavitation of nodules or consolidation is considered rare in the immunocompetent patient [5]. However, a study by Fox and Müller [2] noted cavitation in approximately 42% of patients. A solitary cryptococcal nodule or mass may simulate lung cancer [4].
Fox and Müller [2] reported that CT manifestations and the clinical presentation were influenced by patient age. In that series, six patients who were older than the median age of 44 years presented with only one or two peripheral nodules and were asymptomatic. An additional six patients with multiple nodules, consolidation, or cavitation were younger than the median age, and of these, five were symptomatic and one was asymptomatic. Miliary dissemination, cavitation, lymphadenopathy, and pleural effusions are rare in immunocompetent patients and frequently seen in immunocompromised patients [2, 4].
Sputum cultures are not reliable and serum titers are usually not elevated except in disseminated disease [4]. Therefore, the diagnosis depends on biopsy and pathologic confirmation of the mucinous yeast capsule that stains strongly positive, bright red with mucicarmine. A methenamine silver stain reveals yeast forms with no evidence of budding. On PAS (periodic acid-Schiff) stains, the organism appears as a pale round structure [6].
For cryptococcal pneumonia in asymptomatic immunocompetent patients, careful observation only may be warranted [7]. For symptomatic or immunocompromised patients, oral fluconazole (Diflucan, Pfizer) is the antifungal agent commonly used. Prognosis depends on immunological status and underlying comorbidities.
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