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

Abstract

본 저자는 MALT 림프종으로 치료 중인 환자에서 양전자단층촬영술상 뇌하수체에 국소적인 FDG 섭취가 관찰되었고 안장 자기공명영상에서는 라트케열 낭으로 의심되는 소견이 발견되었으나, 호르몬검사상 비기능성 뇌하수체 선종으로 의심되는 사례를 경험하였기에 이를 보고하는 바이다.

Magnetic resonance imaging (MRI) is the modality of choice for the detection and characterization of a pituitary adenoma. Uptake of 18F-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 α-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.