Case report Uptake of 2-[ 18 F]fluoro-2-deoxy-D-glucose in uterine leiomyoma: imaging of four patients by coincidence positron emission tomography I ˙ lknur Ak a , Sinan O ¨ zalp b ,O ¨ mer T. Yalc ¸ in b , Evren Zor a and Erkan Vardareli a Uterine leiomyomas, benign tumours of the human uterus, are the most common uterine neoplasm and are composed of smooth muscle with varying amounts of fibrous connective tissue. As a functional imaging modality, 2-[ 18 F]fluoro-2-deoxy-D-glucose ( 18 F-FDG) positron emission tomography can be used to obtain information about glucose metabolism in tissues. In this study, the findings of the 18 F-FDG scans of four patients who were suspected of having malignant gynaecological tumours because of clinical and radiological findings and finally diagnosed as uterine leiomyoma based on histopathological examination were evaluated. Moderately intense 18 F-FDG accumulation was detected in uterine mass localization in lower pelvis. The reason for the accumulation of 18 F-FDG in uterine leiomyomas is not known. It may be explained by the existence of higher levels of growth factors, including basic fibroblast growth factor, transforming growth factor beta, granulocyte-macrophage colony-stimulating factor and receptors, and proliferation of smooth muscle cells in leiomatous uterus. Nucl Med Commun 25:941–945  c 2004 Lippincott Williams & Wilkins. Nuclear Medicine Communications 2004, 25:941–945 Keywords: uterine leiomyoma, 18 F-FDG, coincidence PET Departments of a Nuclear Medicine and b Obstetrics and Gynecology, Osmangazi University Faculty of Medicine, Eski ¸ sehir, Turkey. Correspondence to Dr I ˙ lknur Ak, Osmangazi University Medical Faculty, Department of Nuclear Medicine, 26480 Eski ¸ sehir, Turkey. Tel: +90 222 239 2979 or 3450; fax: +90 222 229 1150; e-mail: ilknur_ak@yahoo.com Received 14 November 2003 Accepted 11 March 2004 Introduction Uterine leiomyomas (fibroids or myomas), benign tu- mours of the human uterus, are the most common uterine neoplasm and are composed of smooth muscle with varying amounts of fibrous connective tissue. They are clinically apparent in about 25% of women and the most common solid pelvic tumours [1]. With newer imaging techniques, the true clinical prevalence may be higher. Careful pathological examination of surgical specimens suggests that the prevalence is as high as 77% [2]. Although most leiomyomas are asymptomatic, patients may present with abnormal uterine bleeding, pressure on adjacent organs, pain, infertility, or a palpable abdominal– pelvic mass. The size of uterine leiomyomas is variable, ranging from microscopic to large tumours that fill the abdomen. The diagnosis of myomas is often suspected on the basis of palpation of an enlarged irregular uterine contour on pelvic examination. Ultrasonography (USG) is typically used to confirm the diagnosis and exclude the possibility of ovarian neoplasm. Magnetic resonance imaging (MRI) gives better visualization of individual myomas and it is currently considered the most accurate imaging technique for detection and localization of leiomyomas [3,4]. Their typical appearances at MRI have been well established. Because of its ability to clearly demonstrate individual tumours, MRI has been shown to be more sensitive than USG in detection of leiomyomas [5]. However, cases that are extremely difficult to differentiate from other conditions are occasionally encountered. Unlike with MRI, accurate assessment of an enlarged, myomatous uterus ( > 140 cm 3 ) is not consistently possible with USG because of the limited field of view [6]. Positron emission tomography (PET) with 2-[ 18 F]fluoro- 2-deoxy-D-glucose ( 18 F-FDG) has opened a new field in clinical imaging, thereby differing from the more conventional morphological or anatomical imaging meth- ods, including radiography, USG, computed tomography (CT), MRI and even single photon emission tomography (SPET). It has been used successfully for assessing the large variety of primary tumours and metastases, prog- nosis, and planning and for monitoring tumour therapy as well as for early detection of recurrent tumour growth. As a functional imaging modality, 18 F-FDG PET represents the information about glucose metabolism of tissues. The glucose analogue 2-deoxy-D-glucose is transported into the cell in the same way as glucose. In the cell, it is phosphorylated to deoxyglucose-6-phosphate by hexo- kinase, like normal glucose. However, in contrast with glucose, glucose-6-phosphate isomerase does not react with deoxyglucose-6-phosphate, so further metabolism is not possible. In addition, deoxyglucose-6-phosphate shows slow clearance from the cell, which is caused by low membrane permeability. Thus, deoxyglucose-6-phos- phate is trapped in the cell [7]. 18 F-FDG imaging can be 0143-3636  c 2004 Lippincott Williams & Wilkins Copyright © Lippincott Williams & Wilkins. Unauthorized reproduction of this article is prohibited.