Retro-orbital, Breast, Cardiac, Skin, and Subcutaneous Metastases of Neuroendocrine Tumor From a Tail Gut Cyst on 68Ga-DOTATATE PET/CT Imaging

Radiolabeled Somatostatin Analogs for Cancer Imaging

Somatostatin receptors (SSTR) are expressed by many tumours especially those related to neuro-endocrine origin and molecular functional imaging of SSTR expression using radiolabelled somatostatin analogs have revolutionized imaging of patients with these group of malignancies. Coming a long way from the first radiolabelled somatostatin analog 123I-Tyr-3-octreotide, there has been significant developments in terms of radionuclides used, the ligands and somatostatin derivatives. 111In-Pentetreotide extensively employed for imaging NETs at the beginning has now been replaced by 68Ga-SSA based PET-CT. SSA-PET/CT performs superior to conventional imaging modalities and has evolved in the mainframe for NET imaging. The advantages were multiple: (i) superior spatial resolution of PET versus SPECT, (ii) quantitative capabilities of PET aiding in disease activity and treatment response monitoring with better precision, (iii) shorter scan time and (iv) less patient exposure to radiation. The modality is indicated for staging, detecting the primary in CUP-NETs, restaging, treatment planning (along with FDG: the concept of dual-tracer PET-CT) as well as treatment response evaluation and follow-up of NETs. SSA PET/CT has also been incorporated in the guidelines for imaging of Pheochromocytoma-Paraganglioma, Medullary carcinoma thyroid, Meningioma and Tumor induced osteomalacia. At present, there is rising interest on (a) 18F-labelled SSA, (b) 64Cu-labelled SSA, and (c) somatostatin antagonists. 18F offers excellent imaging properties, 64Cu makes delayed imaging feasible which has implications in dosimetry and SSTR antagonists bind with the SST receptors with high affinity and specificity, providing high contrast images with less background, which can be translated to theranostics effectively. SSTR have been demonstrated in non-neuroendocrine tumours as well in the peer-reviewed literature, with studies demonstrating the potential of SSA PET/CT in Neuroblastoma, Nasopharyngeal carcinoma, carcinoma prostate (neuroendocrine differentiation) and lymphoma. This review will focus on the currently available SSAs and their history, different SPECT/PET agents, SSTR antagonists, comparison between the various imaging tracers, and their utility in both neuroendocrine and non-neuroendocrine tumors.

Liver metastases of a neuroendocrine tumor arising from a tailgut cyst treated with interventional locoregional therapies: a case report and review of the literature on recurrent cases

A tailgut cyst is a rare, developmental cyst occurring in the presacral space. Although primarily benign, malignant transformation is a possible complication. Herein, we report a case of liver metastases after resection of a neuroendocrine tumor (NET) arising from a tailgut cyst. A 53-year-old woman underwent surgery for a presacral cystic lesion with nodules in the cyst wall. The tumor was diagnosed as a Grade 2 NET arising from a tailgut cyst. Thirty-eight months after surgery, multiple liver metastases were identified. The liver metastases were controlled with transcatheter arterial embolization and ablation therapy. The patient has survived for 51 months after the recurrence. Several NETs derived from tailgut cysts have been previously reported. According to our literature review, the proportion of Grade 2 tumors in NETs derived from tailgut cysts was 38.5%, and four of the 5 cases of Grade 2 NETs (80%) relapsed, while all eight cases of Grade 1 NETs did not relapse. Grade 2 NET may be a high-risk group for recurrence in NETs arising from tailgut cysts. The percentage of Grade 2 NETs in tailgut cysts was higher than that of rectal NETs, but lower than that of midgut NETs. To the best of our knowledge, this is the first case of liver metastases of a neuroendocrine tumor arising from a tailgut cyst that was treated with interventional locoregional therapies, and the first report to describe about the degree of malignancy of neuroendocrine tumors originating from tailgut cysts in terms of the percentage of Grade 2 NETs.

Management of Incidental Breast Lesions Detected at Nuclear Medicine Examinations

Nuclear medicine studies are often performed in patients with breast cancer; however, incidental radiotracer uptake in the breasts can be observed in patients with nonbreast malignancies. Benign and malignant lesions can be identified on planar, SPECT, and PET scans. This review will outline the molecular and radiographic imaging appearance of benign and malignant breast lesions on sestamibi scans, bone scans, radioiodine studies, as well as PET studies using fluorine 18 (¹⁸F) fluorodeoxyglucose, gallium 68 (⁶⁸Ga) tetraazacyclododecane tetraacetic acid octreotate (or DOTATATE), ⁶⁸Ga prostate-specific membrane antigen, and ¹⁸F-fluciclovine radiotracers. Recognizing these lesions at molecular and anatomic imaging is important to ensure accurate diagnosis and appropriate management. Keywords: Breast, Mammography, Molecular Imaging, PET/CT, Radionuclide Studies, SPECT/CT © RSNA, 2020.

Neuroendocrine tumour developing within a long-standing tailgut cyst: case report and review of the literature

A tailgut cyst is a rare congenital lesion that can develop in the presacral space from the remnants of an embryonic hindgut. It is unusual for malignant change to occur in a tailgut cyst. We report a case of a large long-standing tailgut cyst, which was removed during a laparotomy. Histopathology showed a well-differentiated neuroendocrine tumour (primary carcinoid tumour) arising in a tailgut cyst. We reviewed the English literature for all adult cases with this condition. All original articles were reviewed, and data were compiled and tabulated. Including this report, 29 cases of NET developing in a tailgut cyst were found in the English literature. Tailgut cysts have been reported as more common in females, with a mean age of presentation in the fifth decade (Devine, in: Zbar A, Wexner S (eds) Coloproctology. Springer specialist surgery series, Springer, London, 2010; Hjermstad and Helwig in Am J Clin Pathol 89:139-147, 1988). Tailgut cysts may undergo malignant change including adenocarcinoma, sarcoma, and NET (Mathis et al. Br J Surg 97:575-579, 2010; Messick in Dis Colon Rectum 61:151-153, 2018; Patsouras et al. in Colorectal Dis 17:724-729, 2015; Chereau et al in Colorectal Dis 15:e476-e482, 2013). It is difficult to estimate the true incidence of malignant change in a tailgut cyst, with the literature reports only limited to case reports and small-case series. Although rare, our case confirms need to consider the possibility of a malignant component, even in a benign process such as a tailgut cyst. This prompts consideration for upfront definitive management.

Incidental Orbital Neuroendocrine Metastases on 111In-OctreoScan and MRI

Neuroendocrine tumors have a propensity to metastasize, but rarely to the orbits. A 69-year-old woman with history of neuroendocrine tumor of pancreatic primary underwent routine follow-up In-pentetreotide (OctreoScan) imaging, with 24-hour whole-body planar images showing subtle right periorbital tracer uptake that localized to extraocular muscles on subsequent SPECT/CT. Orbital MRI further defined the location of these highly suspicious orbital metastases, which were treated with external radiation, with follow-up MRI showing decreased size of the orbital metastases. Early identification and treatment of orbital metastases is critical to help preserve vision and quality of life.