Increased MIBG Activity in the Uterine Cervix Due to Menstruation

Abstract

A 21-year-old woman with history of presacral ganglioneuroblastoma underwent I-MIBG scan for restaging. Planar images revealed increased MIBG activity in the upper pelvis, suggestive of disease recurrence. Complementary SPECT/CT images, however, localized the activity to the uterine cervix. Upon further questioning, it has been established that the patient was menstruating. Subsequent follow-up scans proved normal, confirming the benign etiology of these findings. The case shows that radioactive blood accumulation in the uterine cervix can interfere with MIBG scan interpretation in menstruating patients.

Menstruation Confounding the Correct Interpretation of 99mTc-RBC Bleeding Scan

“…Although false-positive interpretations of 99m TcO 4 − Meckel scintigraphy also occur, 5,6 the application of SPECT/CT, as in our case, can improve the diagnostic accuracy of test 7 . Uterus uptake during menstruation in other nuclear medicine modalities has also been reported previously, including 18 F-FDG, 8 68 Ga-FAPI, 9 99m Tc-Mag3, 123 I-MIBG, 10 and 131 I 11 . Many potential false-positive findings can occur in the 99m Tc-RBC bleeding, including arteriovenous malformation, 12 pelvic kidney, 13 hepatic hemangioma, 14 dilated mesenteric veins, 15 varices, 16–18 gallbladder in patients with renal failure, 19 and aortic aneurysm 20 .…”

MIBG Uptake in a Gastric Gastrointestinal Stromal Tumor

“…However, false-positive findings do occur in many different situations. [6][7][8] MIBG uptake in GIST have been reported before. 9,10 Recognizing abnormal activity caused by gastric GIST is important because gastric MIBG activity can be a normal variant.…”

“…MIBG imaging is generally regarded as very specific study. However, false-positive findings do occur in many different situations 6–8 . MIBG uptake in GIST have been reported before 9,10 .…”