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Incidental detection of clinically occult follicle stimulating hormone secreting pituitary adenoma on whole body 18-Fluorodeoxyglucose positron emission tomography-computed tomography
Address for correspondence: Dr. Prathamesh Joshi, Department of Nuclear Medicine and PET-CT, Jaslok Hospital and Research Centre, Worli, Mumbai – 400 026, India. E-mail: drprathamj@gmail.com
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This article was originally published by Medknow Publications and was migrated to Scientific Scholar after the change of Publisher.
Abstract
A 73-year-old man, known case of Hodgkin's lymphoma, underwent 18-Fluorodeoxyglucose positron emission tomography-computed tomography (18-FDG PET-CT) for post-chemotherapy evaluation of the disease status. The scan revealed focal increased FDG uptake in pituitary fossa. The CT images showed homogenously enhancing pituitary lesion causing expansion of the sella. A possibility for the presence of pituitary adenoma was raised in the report. Hormonal assay of the patient showed raised follicle stimulating hormone (FSH) level of 18 IU/ml (normal range for males up to 5 IU/ml). All the other pituitary hormones were within the normal range. Nuclear magnetic resonance (NMR) imaging of brain showed a pituitary lesion with expanded sella pushing the optic chiasma superiorly. NMR findings confirmed the presence of pituitary macroadenoma. A final diagnosis of FSH secreting pituitary macroadenoma was made.
Keywords
18-Fluorodeoxyglucose positron emission tomography-computed tomography
follicle stimulating hormone
nuclear magnetic resonance
pituitary adenoma
INTRODUCTION
We report a case where incidental 18-Fluorodeoxyglucose (18-FDG) uptake in pituitary fossa was noted in positron emission tomography-computed tomography (PET-CT), which on further investigations was found to be clinically occult follicle stimulating hormone (FSH) secreting pituitary macroadenoma.
CASE REPORT
A 73-year-old man, known case of Hodgkin's lymphoma, underwent 18-FDG PET-CT for post-chemotherapy evaluation of the disease status. The scan revealed focal increased FDG uptake in pituitary fossa [Figure 1a and b]. The Maximum Standardized Uptake Value was 2.1 cm2/ml. The sagittal reformatted CT image [Figure 2a] showed homogenously enhancing pituitary lesion causing expansion of the sella, and axial contrast CT image [Figure 2b] showed mildly enhancing rounded lesion in the sella abutting the tuberculum and dorsum sella anteriorly and posteriorly. A possibility for the presence of pituitary adenoma was raised in the report.
Nuclear magnetic resonance (NMR) imaging of brain confirmed the presence of pituitary macroadenoma. High-resolution, T1-weighted, contrast-enhanced, fat-suppressed sagittal image [Figure 3a] showed the pituitary lesion, with expanded sella pushing the optic chiasma superiorly, and high-resolution, T1-weighted, contrast-enhanced, fat-suppressed axial image [Figure 3b] showed homogenously enhancing sellar lesion abutting the cavernous segment of bilateral internal carotid arteries. Hormonal assay of the patient showed raised FSH level of 18 IU/ml (normal range for males up to 5 IU/ml). All the other pituitary hormones were within the normal range. A diagnosis of clinically occult FSH secreting pituitary macroadenoma was made.
DISCUSSION
Incidental pituitary FDG uptake is an extremely rare finding. A study revealed that the incidence of focally increased FDG uptake in pituitary is only 0.073%.[1] The pituitary adenoma may have high FDG uptake.[2] The mean SUVmax calculated without correction for partial volume effect for macroadenomas is reported to be significantly higher than the SUVmax for microadenomas.[1] Pituitary adenomas are the most common cause of pituitary hormone hypersecretion and hyposecretion syndromes in adults. They account for around 15% of all intracranial neoplasms.[3] Isolated gonadotropin secreting pituitary adenoma with increased levels of circulating FSH, as in our case, is a very rare occurrence.[4]
Our case demonstrates the importance of further evaluations, including hormone assays and NMR imaging of the pituitary, to diagnose clinically occult pituitary adenoma when incidental increased pituitary FDG uptake is noted.
Source of Support: Nil
Conflict of Interest: None declared.
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