68Ga-DOTATATE PET/MR Imaging of Urinary Bladder Paraganglioma

Mesenchymal neoplasms of the urinary bladder: a comprehensive review with focus on cross-sectional imaging findings

Mesenchymal neoplasms of the urinary bladder are exceedingly rare and display remarkable diversity. These tumors demonstrate distinct pathological features as well as variable biological behavior and cross-sectional imaging findings. The rarity of tumors, nonspecific symptoms and seemingly normal cystoscopic findings (particularly with small and exophytic tumors) frequently lead to misdiagnosis or missed diagnosis. While some tumors display characteristic cross-sectional imaging findings that may suggest a diagnosis, imaging findings are mostly nonspecific. Histopathological examination is required for accurate diagnosis, management and prognostication. The purpose of this article is to review the cross-sectional imaging findings of a diverse spectrum of mesenchymal tumors of the urinary bladder.

Site-based performance of 131I-MIBG imaging and 99mTc-HYNIC-TOC scintigraphy in the detection of nonmetastatic extra-adrenal paraganglioma

OBJECTIVES

This study aimed to evaluate the performance of 131I-metaiodobenzylguanidine (MIBG) imaging to detect nonmetastatic extra-adrenal paragangliomas at their respective sites (abdominal vs. thoracic vs. head and neck vs. urinary bladder), and compare it with that of 99mTc-hydrazinonicotinyl-tyr3-octreotide (HYNIC-TOC) scintigraphy.

METHODS

We retrospectively analyzed 235 patients with nonmetastatic extra-adrenal paragangliomas who underwent preoperative 131I-MIBG imaging or 99mTc-HYNIC-TOC scintigraphy. Of all 235 patients, 145 patients underwent both imaging procedures, 16 patients 131I-MIBG imaging only and 74 patients 99mTc-HYNIC-TOC scintigraphy only.

RESULTS

The overall sensitivity of 131I-MIBG and 99mTc-HYNIC-TOC imaging to detect extra-adrenal paragangliomas regardless of tumor sites was 75.8% (122/161) and 67.6% (148/219), respectively (P = 0.082). However, when stratified by tumor sites, 131I-MIBG imaging showed a significant improvement in the detection of extra-adrenal abdominal paragangliomas with a sensitivity of 90.3% (103/114), which was significantly higher than that of 99mTc-HYNIC-TOC scintigraphy (67.6% (96/142); P = 0.000). In addition, the intensity of tracer uptake in the extra-adrenal abdominal paragangliomas with 131I-MIBG imaging was evidently higher than with 99mTc-HYNIC-TOC scintigraphy. The sensitivity of 131I-MIBG imaging and 99mTc-HYNIC-TOC scintigraphy to detect urinary bladder, head and neck, and thoracic paragangliomas were 18.7 vs. 18.5% (P = 1.000); 17.4% vs. 84.6% (P = 0.000) and 60% vs. 94.4% (P = 0.030), respectively.

CONCLUSIONS

131I-MIBG imaging could become the first-line investigation modality in patients with extra-adrenal abdominal paragangliomas. However, 99mTc-HYNIC-TOC scintigraphy has high sensitivity and is superior to 131I-MIBG imaging for detecting head & neck and thoracic paraganglioma. Both 131I-MIBG imaging and 99mTc-HYNIC-TOC scintigraphy have poor performance for detecting urinary bladder paragangliomas.

[68Ga]-DOTATATE PET/MRI in the diagnosis and management of recurrent head and neck paraganglioma with spinal metastasis

Most head and neck paragangliomas (PGLs) are biochemically silent and often present with recurrence and metastases in association with hereditary syndromes. Whole-body functional imaging is increasingly used to detect tumor extent and guide treatment planning of PGLs. [68Ga]-DOTATATE, which targets somatostatin receptor 2 (SSTR2) overexpression, has emerged as a sensitive functional imaging modality in PGLs. We present a patient with metastatic glomus caroticum PGL in whom [68Ga]-DOTATATE PET/MRI provided a more accurate characterization of metastatic extent, as compared to gadolinium-enhanced MRI of the neck and whole body [18F]-FDG PET/CT. We then review the current literature and discuss the imaging implications of [68Ga]-DOTATATE PET/MRI in PGLs.

Paraganglioma From Vaginal Wall Revealed by 131I-MIBG Scan

ABSTRACT

Vaginal paraganglioma is very rare. Most patients first presented irregular heavy menses and abnormal vaginal bleeding. The accurate diagnosis can only be made pathologically. Here we report a case of paraganglioma arising from vaginal wall in a 44-year-old woman who only presented catecholamine-related symptoms. The lesion had negative 99mTc-HYNIC-TOC (hydrazinonicotinyl-Tyr3-octreotide) activity but positive on 131I MIBG scan. Paraganglioma was highly suspected, which was confirmed by pathological and immunohistochemical findings after surgical resection of the lesion.

Unsuspected Bladder Diverticulum Resulted in False-Positive 68Ga-DOTATATE Uptake

ABSTRACT

A 67-year-old woman with medullary thyroid cancer was referred for a 68Ga-DOTATATE PET/CT scan for staging. The images showed abnormal activity in the left thyroid gland and the left cervical lymph nodes. Surprisingly, increased activity was also noted in the posterolateral aspect of the urinary bladder without corresponding anatomical abnormality. This activity disappeared after urination, suggesting false-positive uptake due to bladder diverticulum.