J Korean Endocr Soc.  2008 Apr;23(2):137-141. 10.3803/jkes.2008.23.2.137.

Non-functional Pituitary Adenoma Detected on (18)F-fluorodeoxyglucose Positron Emission Tomography ((18)F-FDG-PET) in a Patient with Mucosa-associated Lymphoid Tissue Lymphoma

• Lee JH
• Han SJ
• Park SE
• Cho MA
• Cheong JW
• Yun M
• Rhee Y
• Lee EJ
• Lim SK

• KMID: 2063565
• DOI: http://doi.org/10.3803/jkes.2008.23.2.137

Abstract

Magnetic resonance imaging (MRI) is the modality of choice for the detection and characterization of a pituitary adenoma. Uptake of (18)F-fluorodeoxyglucose (FDG) by intrasellar tumors, including pituitary adenomas, has been reported in several previous studies. We report a case where a pituitary adenoma was detected on FDG-positron emission tomography (PET), but the tumor was not detected with the use of sellar MRI. A 31-year-old woman was referred to the clinic due to a focal increase of FDG uptake at the pituitary fossa seen on whole body FDG-PET. The patient was receiving chemotherapy due to a recurred B-cell lymphoma of the mucosa-associated lymphoid tissue type. Subsequently, sellar MRI was performed, and images showed a small non-enhancing heterogenous cystic lesion in the midline of the pituitary gland, radiologically suggestive of a Rathke's cleft cyst. However, sellar MRI failed to identify a lesion consistent with a pituitary tumor that corresponded to the site of increased FDG uptake detected by the use of PET, despite the inclusion of a dynamic contrast enhanced sequence. Despite the negative findings of the MRI examination, basal and stimulated levels of the GnRH free alpha-subunit were profoundly increased. Therefore, we suspected the presence of a non-functional pituitary tumor in addition to a Rathke's cleft cyst, rather than pituitary involvement of a lymphoma, based on the hormone levels and PET scan findings.

Keyword

lymphoma; non-functioning pituitary adenoma; PET

MeSH Terms

Adult
Electrons
Female
Gonadotropin-Releasing Hormone
Humans
Lymphoid Tissue
Lymphoma
Lymphoma, B-Cell
Lymphoma, B-Cell, Marginal Zone
Magnetic Resonance Imaging
Pituitary Gland
Pituitary Neoplasms
Positron-Emission Tomography
Gonadotropin-Releasing Hormone

Figure

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  Fig. 1 Midline sagittal section and coronal section of 18F-FDG-PET. Focal FDG uptake at the pituitary gland (arrow).

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  Fig. 2 GnRH and TRH stimulation test. The basal and GnRH stimulated levels of free α-subunit were increased more than three times the normal range. TRH stimulation test showed no significant change.

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  Fig. 3 Midline sagittal image of gadolinium-enhanced T1 (A), T2 (B) weighted MRI and coronal image of dynamic (C),. gadolinium-enhanced T1 (D). A small non-enhancing nodule in the middle portion of pituitary gland, suggestive of Rathke's cleft cyst (arrow).

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