- © 2009 by American Society of Clinical Oncology
[18F]Fluorodeoxyglucose-Avid Adrenal Masses Due to Histoplasmosis
A 60-year-old poultry worker with smoking history presented to the preventive oncology/cancer screening program with cough, intermittent fever and weight loss of 10 kg in 2 months. His chest radiograph and routine blood investigations were normal. Considering the patients age and clinical presentation there was a suspicion of malignancy and hence a computed tomography (CT) scan of the chest and abdomen was performed. It did not reveal any significant abnormality except for bilateral enlarged adrenal glands with a heterogeneous appearance (Fig 1A). The patient then was referred for [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET)/CT study for further evaluation of the adrenal masses and to look for any other pathology. After intravenous injection of 370 MBq of FDG, following an uptake period of 60 minutes, a whole-body scan was done on a dedicated PET/CT scanner. It revealed increased FDG concentration in both the enlarged adrenal glands (Fig 1B) on the PET images and on the fused PET/CT images (Fig 1C). Rest of the whole-body scan was unremarkable and showed physiological uptake (Fig 1D). An ultrasonography-guided fine-needle aspiration cytology was done from the right gland which revealed micro-organic fungal growth—Histoplasma capsulatum. The microscopic images showed histiocytes stuffed with H capsulatum (Fig 2A, Giemsa ×400; Fig 2B, Giemsa ×1,000). Histoplasmosis of the adrenals was thus established. The patient was offered symptomatic and supportive treatment for fever in addition to an oral course of antifungal medication (itraconazole 200 mg daily, initially for 15 days). However, the patient went back to his village and has not followed up at our hospital since then.
Histoplasmosis, a condition caused by H capsulatum, affects the pulmonary system primarily causing cavitating fungal lesions.1 The patients routinely do not reveal any symptoms, but develop symptoms in cases with disseminated disease or when the patients are immunocompromised. The fungus has an affinity for the mononuclear phagocytes (histiocytes) that form the reticulo-endothelial system. Hence there is involvement of the liver, spleen, lymph node, bone marrow, and adrenal gland in disseminated disease.1 These patients have clinical signs identical to tuberculosis, with fluid-filled cavities and atelectasis, and develop symptoms of cough, weight loss, fevers, and malaise. The disease may spread hematologically and remain dormant, and then reactivate in states of reduced immunity. Fifty percent of the cases of disseminated disease have an adrenal insufficiency and lead to fatal sequelae. The characteristic CT findings of the adrenal gland in disseminated disease appear as bilateral symmetric enlargements with low-density areas of focal hemorrhage and necrosis. The glands tended to maintain their normal shape. In chronic phases there may be calcification due to healing.2,3 It is demonstrated that FDG PET has a high sensitivity and specificity ranging between 80% and 100% for differentiating malignant from benign adrenal masses.4 However, a recent study of 105 patients with adrenal lesions on CT scan on comparison with FDG PET scan studies showed FDG PET helped in differentiating benign versus malignant adrenal tumors in situations where the probability of malignancy was high, but showed an inconsistent pattern for endocrine tumors. This study supports the earlier data that PET helps to localize and characterize adrenal tumors.5 Literature search has shown a case report of bilateral adrenal masses showing high FDG uptake in a case of histoplasmosis,6 but similar findings are also seen in cases with tubercular adrenal involvement.7 As the treatment modalities in all these vary, it is mandatory to obtain histopathological confirmation of the disease. There is evidence to show that a image-guided fine-needle aspiration biopsy from the adrenal gland is sufficient to get tissue diagnosis.8,9,10 Adrenal histoplasmosis has been described in nonendemic regions and in immunocompetent patients.11,12 Our case shows adrenal histoplasmosis as an unusual cause of bilateral adrenal uptake of FDG in an immunocompetent individual from a nonendemic area with no other organ involvement. It emphasizes the fact that histopathology is important to establish the diagnosis when enlarged FDG-avid adrenal glands are seen on PET, particularly in regions where infections such as tuberculosis and histoplasmosis are endemic. This case also shows how FDG PET can be a useful tool to guide biopsy in such clinical situations.
AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST
The author(s) indicated no potential conflicts of interest.
