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Robert Wood Johnson Medical School at Camden, Camden, NJ
INTRODUCTION: We report a cryptococcoma in a normal host presenting as a pulmonary mass with a "false positive" 99mTc depreotide scan.
CASE PRESENTATION: A 48-year-old man presented with a 4x3 cm mass not present 16 months earlier. Computed tomographic scans confirmed the presence of an isolated left lower lobe mass surrounded by normal parenchyma. The patient denied all respiratory and systemic symptoms. Past medical history was significant only for "walking pneumonia" years earlier. He denied human immunodeficiency virus risk factors, tuberculosis exposure, significant travel history, and use of tobacco, alcohol, and recreational drugs. Physical examination was unremarkable.
A 99mTc depreotide scan (Graphic 1) showed intense left lower lobe uptake corresponding with the roentgenographic abnormality. Bronchoscopy was unremarkable, with negative smears, cultures, acid fast stains, fungal stains, and cytology.
The mass was resected. Pathology revealed a solitary peripheral mass. Histologic section (Graphic 2) demonstrated extensive granulomatous involvement of the pulmonary parenchyma with multinucleated giant cells containing abundant GMS-positive yeast forms. Their capsules were focally but not uniformly positive for mucicarmine (Graphic 3). The staining is characteristic for Cryptococcus neoformans.
The patient completed six weeks of oral Fluconazole.(1) He remains asymptomatic.
DISCUSSION: To our knowledge, this is the first reported case of a depreotide-positive cryptococcoma. Cryptococcoma in a normal host is rare, though reported.(1) This patient was a non-smoker, and the mass had an apparent rapid growth rate which made malignancy less likely, but the lack of an alternative benign diagnosis after bronchoscopy mandated further evaluation. The depreotide study was done with the thought that a negative study would markedly decrease the possibility of cancer and might allow conservative management. As the case evolved, the markedly positive study (coupled with patient preference) led to a decision to resect.
In a recent multicenter study using depreotide, sensitivity and specificity for malignancy were 96.6% and 73% respectively,(2) similar to those of fluorine-18-fluorodeoxyglucose positron emission tomography (PET scanning).(3) Both modalities do have "false positives" in the sense that a positive scan can represent a non-malignant biological process. Reported false positives for depreotide include granulomas, hamartomas, and rounded atelectasis.(345) Reported false positives for PET include caseating granuloma, histoplasma, cryptococcoma, schwannoma, fibrous mesothelioma, tuberculoma, rheumatoid nodule, and "inflammatory lesion."(678) The two modalities are similar not only in their diagnostic accuracy but also in the type of biological process which will create a false positive. One PET-positive cryptococcoma has been reported; this depreotide-positive cryptococcoma is an example of the tendency of both modalities to be positive in areas of granulomatous inflammation.
CONCLUSION: Depreotide and PET scanning can at times be very helpful in the diagnostic work-up of solitary pulmonary masses. Both can be false-positive in cases of granulomatous disease.
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