18 F-FDG PET/CT Findings of Omental Cake: A Case Report Rong-Hsin Yang, Yum-Kung Chu Department of Nuclear Medicine, Taipei Veterans General Hospital, Taipei, Taiwan Received 1/19/2010; revised 2/11/2010; accepted 2/23/2010. For correspondence and reprints contact: Yum-Kung Chu, M.D., Department of Nuclear Medicine, Taipei Veterans General Hospital. 201 Section 2, Shih-Pai Road, Taipei 112, Taiwan. Tel: (886)2-28757374 ext. 7301, E-mail: ykchu@vghtpe.gov.tw Omental cake refers to infiltration of the omental fat by material of soft-tissue density. Diffuse peritoneal and omental seeding are well-known forms of dissemination of metastatic carcinoma. The most common causes are metastases from the ovary, gastrointestinal tract or breast. We present a case of peritoneal carcinomatosis showing the appearance of caking on the PET/CT, with rising of CA-125, CA-153 and CEA. Ascitic fluid cytol- ogy suggested metastatic adenocarcinoma. The role of 18 F-FDG PET/CT in diagnosing peritoneal carcinomato- sis is discussed. Key words: FDG PET/CT, peritoneal carcinomatosis, omental cake Ann Nucl Med Sci 2010;23:93-97 Introduction Cancer of unknown primary site (CUP) is a relatively common clinical entity, accounting for 4% to 5% of all inva- sive cancers. Within this category, tumors from many prima- ry sites with varying biology are represented. This hetero- geneity has made the design and interpretation of clinical studies difficult. Because of its inconclusive imaging, clinical and laboratory features, a multidisciplinary approach may be necessary for a presumptive diagnosis. Being aware of the similarities, between the imaging features of peritoneal carci- nomatosis and other pathological entities, one should consid- er the utility of image-guided core biopsy in order to avoid laparotomy or even erroneous tumor debulking. We report an extensive form of peritoneal carcinomatosis with massive ascites, accompanied by rising of serum CA-125, CA-153 and CEA. The PET/CT images demonstrated markedly increased 18 F-FDG activity of the omental caking seen on the CT scan. Case Report A 71-year-old woman, a known case of HBV carrier and high blood pressure for the past 10 years, was transferred from a neighboring hospital, complaining of anorexia and progressive abdominal distension for 2 months. Examination revealed pitting edema of bilateral legs. Her abdomen was large protruded. However, it was nontender without any pal- pable visceromegaly. Shifting dullness was present and gut sounds were audible. Her deranged serum values were CA- 125 rising of 360 U/ml (normal <35 U/ml), CA-153 of 68 U/ml (normal <31.3 U/ ml) and CEA of 81 ng/ml (normal <3 ng/ml), the results of serum biochemistry were within normal limits otherwise. Chest radiograph showed no specific find- ings apart from bilateral raised diaphragms. Abdomen sono- gram exhibited intrahepatic duct stones and calcified granulo- mae in the liver. The abdomen and pelvis CT (not shown) done for her initial workup exhibited massive ascites, thickening and increased attenuation with nodularity along the greater omen- tum and peritoneum. The findings were consistent with omental caking. There were no evidence of lymphadenopathy and no obvious lesions in the liver, lungs or bones. Gynecologic workup including the sonography and pap-