pulmonary cryptococcosis is a type of fungal infection , initiated by inhalation of the organism , cryptococcus neoformans , from an environmental source ( 1 ) .
it most commonly occurs in immunocompromised hosts , such as human immunodeficiency virus ( hiv)-infected or cancer patients , and rarely involves the immunocompetent hosts ( 1 , 2 ) .
imaging features , associated with pulmonary cryptococcosis , which mimic hematogeneous metastases , are rare in immunocompetent patients .
to our knowledge , this is a rare presentation of pulmonary cryptococcosis with computed tomography ( ct ) characteristics of hematogeneous lung metastases , and it 's valuable to show the pathologic correlation with positron emission tomography ( pet ) scan .
a 49-year - old man was admitted with a complaint of dry cough over the last two weeks , and pulmonary nodules were incidentally found on his chest radiography ( fig .
1a ) at our outpatient department . due to the pulmonary nodules of unknown cause , ct of the chest was arranged .
multiple well - defined nodules ( number : more than 10 ) were observed in both lungs ( fig .
each nodule differed in size , ranging from 4 mm to 12 mm ; moreover , the nodules were randomly distributed in every lobe , accompanied by minimal pleural effusions .
no recent travel history was noted . the physical examination and all the laboratory tests presented no remarkable findings .
however , tumor markers , such as carcinoembryonic antigen , squamous cell carcinoma antigen , and prostate - specific antigen were all detected to be in the normal range .
the gastroscopy and colonoscopy also showed within normal findings . after failing to find any possible primary malignancy , we arranged a whole body 18f - fluorodeoxyglucose ( fdg ) pet scan to evaluate the possible primary malignancy
our preoperative diagnosis of hematogeneous lung metastases was based on the presence of multiple pulmonary nodules of varying sizes , which distributed randomly throughout the lung ; however , the findings of the whole - body fdg pet scan indicated that the nodules were possibly benign .
two nodules each from the right middle and lower lobe were surgically removed ; histopathology revealed a fibrotic nodule with mild peripheral granulomatous inflammation and many cryptococcal spores ( fig .
a series of examinations were performed for greater detail , such as immunoglobulin levels , hiv by enzyme - linked immunosorbent assay , serum and cerebrospinal fluid cryptococcal antigens , but tested negative .
the patient was then administered intravenous fluconazole , shifting to oral drugs 400 mg per day , for three months , after discharge .
the nodules remain stable in size and number , during a one year follow up .
the pulmonary manifestations in patients with cryptococcal infection can present with a variety of appearances , showing from air - space consolidation to ill- or well - defined nodules / masses ( 2 - 7 ) . in some cases ,
mixed associated findings , such as mediastinal lymphadenopathy , pleural effusions or cavitation , may be also noted .
the number of nodules was often less in immunocompetent patients than in the immunocompromised ones ( 6 , 7 ) in our patient , ct scans revealed multiple nodules , demonstrating relatively aggressive characteristics .
the varying sizes of the pulmonary nodules and the random bilateral distribution mimicked the presentation of hematogeneous pulmonary metastases . further , the nodular margins were well - defined without other associated findings , which was difficult to link to an infectious process .
on reviewing recent case studies and articles ( table 1 ) , we noted that most multiple cryptococcal nodules have a tendency to cluster in one or few lobes in the immunocompetent patients , but cryptococcosis may also rarely show scattered nodules , such as in our case .
besides the aggressive nodular pattern , the totally absence of fdg uptake is also rare .
there are only few studies combining the ct pattern showing pulmonary nodules with the discussion of pet signals .
the standardized uptake value ( suv ) of the cryptococcosis in these reports ranged from 0.93 to 11.6 ( 7 , 9 ) . some lesions may be interpreted as benign by showing low suvs . but most cases are interpreted as likely malignant lesions before biopsy because of the high suv ( 9 ) . in our patient ,
a suv of 2.5 has been traditionally used as a cut - off value for differentiating malignancy ( 7 ) , but in pulmonary cryptococcosis , the suv may vary widely , from mild to marked uptake ( 7 , 9 ) . in our patient ,
the intensity of fdg uptake was virtually absent for each lung lesion , which may indicate a low probability of malignancy ( 10 ) .
but fdg uptake generally depends on the size of the nodule . the small size ( 4 - 12 mm ) of nodules , in this case , might also contribute to the absence of fdg uptake ; hence , we decided to perform an open lung biopsy .
histopathologic results explained the cause of absence of fdg uptake : the nodule mainly composed of fibrotic and necrotic changes , with mild inflammatory cell infiltration .
the lack of active inflammatory process told us the reason for absence of fdg pet signals . in conclusion , we report an image presentation of pulmonary cryptococosis , which mimics hematogeneous metastases .
pet did not demonstrate fdg uptake , suggesting a low probability for malignancy , and it correlated well with the pathologic finding : an infectious nodule composed of fibrosis and necrosis .
it might be a crucial piece of information for clinicians when making management decisions , in cases of multiple lung nodules mimicking hematogeneous metastasis .
 the radiologic appearance of multiple discrete pulmonary nodules in immunocompetent patients , with cryptococcal infection , has been rarely described . 
 we describe a case of pulmonary cryptococcosis , presenting with bilaterally and randomly distributed nodules on a computed tomography , mimicking hematogeneous metastases . 
 positron emission tomography does not demonstrate 18f - fluorodeoxyglucose ( fdg ) uptake , suggesting a low probability for malignancy , which is a crucial piece of information for clinicians when making a management decision . 
 we find the absence of fdg uptake correlates with the pathologic finding of an infectious nodule , composed of fibrosis and necrosis . 
INTRODUCTION
CASE REPORT
DISCUSSION