Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography Imagıng in Pseudo Sister Mary Joseph's Nodule

A 40-year-old male patient was presented with a 2-month history of abdominal swelling, night sweating, and 8 kg of weight loss. He had been treated with antitumor necrosis factor (anti-TNF) drug for ankylosing spondylitis for 3 years. Abdominal computed tomography (CT) showed the presence of ascites, peritoneal thickening, and omental cake sign, and peritonitis carcinomatosa was suspected. Fluorodeoxyglucose positron emission tomography/CT (FDG PET/CT) revealed massive peritoneal involvement with high-FDG uptake (maximum standardized uptake value [SUV_max], 6.3; arrows) and a hypermetabolic nodular lesion in the periumbilical region (SUV_max, 3.3; arrowheads) [Figure 1]. Multiple hypermetabolic lymph nodes, pleural effusion, and mild FDG uptake in pleural surfaces were also seen. The albumin concentration of ascitic fluid was 2.72 g/dl, and no malignant cell was present. Ascitic fluid analysis revealed a predominance of lymphocytes and elevated adenosine deaminase level (138 U/l: normal below 50 U/l). A peritoneal biopsy was reported as necrotizing granulomatous peritonitis and panniculitis. No acid-fast bacilli were detected and cultures were negative. The QuantiFERON test gave positive result. Four-drug antituberculosis (TB) therapy was started and significantly improved the patient's symptoms within 2 months.

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Figure 1 Abdominal computed tomography showed the presence of ascites, peritoneal thickening, and omental cake sign, and peritonitis carcinomatosa was suspected. Fluorodeoxyglucose positron emission tomography/computed tomography revealed massive peritoneal involvement with high-fluorodeoxyglucose uptake (maximum standardized uptake value, 6.3; arrows) and a hypermetabolic nodular lesion in the periumbilical region (maximum standardized uptake value, 3.3, arrowheads) [Figure 1]. Multiple hypermetabolic lymph nodes, pleural effusion, and mild fluorodeoxyglucose uptake in pleural surfaces were also seen. Maximum intensity projection (a), coronal (b), axial (c), and sagittal (d) positron emission tomography/computed tomography images are given in the figure

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Similar laparoscopic and imaging findings can be observed in tuberculous peritonitis and peritoneal carcinomatosis. Abdominal TB constitutes 3%–6.7% of cases with extrapulmonary TB, and peritoneal involvement is common.[12] An increased risk of TB has been demonstrated with the use of TNF-α antagonist. Anti-TNF drugs can cause the breakdown of granulomas in latent infection.[3] A case of umbilical nodule caused by abdominal TB has been reported.[4] The anatomic and embryologic peculiarities of the umbilicus make it a weak point for disease spread.[567] In addition to umbilical metastases, umbilical nodules have been reported in benign tumors or lesions (such as omphalitis, granulomas, cutaneous endometriosis, and psoriasis).[8910] Benign umbilical nodules are called pseudo Sister Mary Joseph nodule and have been rarely reported with FDG PET/CT.[1112] This case highlights the need to consider TB in the differential diagnosis of hypermetabolic umbilical nodules, and careful clinical correlation of imaging findings is recommended.