Trends in Presentation and Management of Endogenous Hyperinsulinaemic Hypoglycaemia Over the Last Three Decades at a Tertiary Care Centre (1992-2022).

Introduction: Endogenous hyperinsulinaemic hypoglycaemia (EHH) is characterized by inappropriate insulin secretion from pancreatic beta cells despite low blood glucose concentrations. We aimed to evaluate the secular changes in presentation and management of EHH due to insulinoma/non-insulinoma pancreatogenous hypoglycaemia syndrome (NIPHS) at our centre. Methods: This was a single-centre ambispective study (2014-2022). The clinical, biochemical, hormonal and radiological parameters (n = 63) collected as part of this study were compared with our earlier studies (1992-2005, n = 31; and 2006-2013, n = 35) and with other centres across the world. Results: A total of 63 patients (39 males) with a preoperative diagnosis of EHH (insulinoma, n = 58; and NIPHS, n = 5) and a mean age of 40.7 years were studied. The mean lag time from the onset of symptoms to diagnosis decreased from 4.6 years during the first study period to 1.9 years during this study period. However, the majority presented with fasting hypoglycaemia of 98.4%, and both fasting and postprandial hypoglycaemia of 32%. Exclusive postprandial hypoglycaemia was present in 1.7% of insulinoma. A histopathological diagnosis of insulinoma was made in 52 patients and nesidioblastosis in two patients. Intraoperative ultrasonography (IOUS) and intraoperative palpation (IOP) yielded 100% sensitivity, while endoscopic ultrasonography (EUS) and 68Ga-DOTA-Exendin-4 positron emission tomography/computed tomography (PET/CT) yielded sensitivity of 86% and 85%, respectively, for localizing insulinoma. Resolution of hypoglycaemia was noted in 53 of 57 (93%) patients who underwent surgery with a preoperative diagnosis of insulinoma. Conclusion: We observed a trend towards earlier diagnosis of EHH, increased patient numbers and availability of nuclear imaging techniques for preoperative localization in the last decade compared to earlier.

Unravelling the Reasons Behind Limited Response to Anti-PD Therapy in ATC: A Comprehensive Evaluation of Tumor-Infiltrating Immune Cells and Checkpoints.

Inhibiting the immune checkpoint (ICP) PD-1 based on PD-L1 expression status has revolutionized the treatment of various cancers, yet its efficacy in anaplastic thyroid carcinoma (ATC) remains limited. The therapeutic response depends upon multiple factors, particularly the conduciveness of the tumor's immune milieu. This study comprehensively evaluated and classified ATC's immune microenvironment (IME) to elucidate the factors behind suboptimal response to anti-PD therapy. Utilizing multiplex-immunofluorescence and immunohistochemistry, we retrospectively analyzed 26 cases of ATC for expression of ICPs PD-L1, PD-1, CTLA4, TIM3, and Galectin-9 and tumor-infiltrating cytotoxic T lymphocytes (CTL)-the effector cells, the anti-tumor NK cells, the immune-inhibitory myeloid-derived suppressor (MDSC) and regulatory T (Treg) cells, and B lymphocytes. Most ATCs (65%) exhibited PD-L1 positivity, but only 31%, in addition, had abundant CTL (type I IME), a combination associated with a better response to ICP inhibition. Additionally, PD-1 expression levels on CTL were low/absent in most cases-a "target-missing" situation-unfavorable for an adequate therapeutic response. All but one ATC showed nuclear Galectin-9 expression. The documentation of nuclear expression of Galectin-9 akin to benign thyroid is a first, and its role in ATC pathobiology needs further elucidation. In addition to less abundant PD-1 expression on CTL, the presence of MDSC, Treg, and exhausted cytotoxic T lymphocytes in the immune milieu of ATC can contribute to anti-PD resistance. TIM3, the most frequently expressed ICP on CTL, followed by CTLA4, provides alternate therapeutic targets in ATC. The co-expression of multiple immune checkpoints is of great interest for ATC since these data also open the avenue for combination therapies.

Odd Sites of Parathyroid Adenomas: 18F-fluorocholine PET/CT Pointing to the Right Place.

Primary hyperparathyroidism is mostly caused by parathyroid adenoma(s) which are generally localized using routine imaging modalities such as neck ultrasonography and 99mTc-SestaMIBI scintigraphy. However, these can miss ectopic parathyroid adenomas due to their limited sensitivities. These ectopic lesions can later lead to failure of surgical excision and necessitate the need for a re-exploration. 18F-fluorocholine (FCH) positron emission tomography/computed tomography (PET/CT) can help in the localization of these ectopic adenomas due to its superior detection rates and spatial resolution. Herein, we report a case of ectopic parathyroid adenomas that were localized on FCH PET/CT.

68 Ga-DOTANOC PET/CT in 2 Siblings With Von Hippel-Lindau Disease.

ABSTRACT: Von Hippel-Lindau disease is a rare multisystem disorder that shows autosomal dominant inheritance. It is a cancer syndrome that is characterized by the development of a variety of benign and malignant tumors-CNS hemangioblastomas, retinal angiomas, endolymphatic sac tumors, renal cysts and tumors, pancreatic cysts and tumors, adrenal pheochromocytomas, and epididymal cystadenomas. Here we present the 68 Ga-labeled DOTANOC scans of 2 siblings who show an interesting spectrum of findings consistent with Von Hippel-Lindau disease.

Pulmonary Mucoepidermoid Carcinoma Mimicking Carcinoid Lung on 18 F-FDG and 68 Ga-DOTANOC PET/CT.

ABSTRACT: Pulmonary mucoepidermoid carcinoma (PMEC) is a rare pulmonary neoplasm. Although 18 F-FDG PET/CT has been shown to present with increased metabolic activity in PMEC, literature does not report increased somatostatin receptor expression in these tumors. We present the case of a 15-year-old boy where PMEC mimicked a typical carcinoid of the lung on DOTANOC PET/CT by showing significant uptake on 68 Ga-DOTANOC.

Role of FDG PET/CT in definitive and presumed autoimmune encephalitis.

OBJECTIVE: F-18 Fluorodeoxyglucose PET/CT (FDG-PET) is emerging as a useful imaging adjunct to MRI in the initial diagnostic evaluation of autoimmune encephalitis (AIE)-though presently it is not included in the diagnostic criteria. MATERIALS AND METHODS: In this prospective study we enrolled a total of 52 patients with clinically diagnosed and treated AIE. MRI evaluation was done in each case along with CSF and EEG where feasible. FDG-PET was done for all and images were interpreted visually and using SPM. RESULTS: The mean age group of patients included was 38.5 ± 22.6 years with 31 females and 21 males. 23 antibody-positive cases underwent PET, the most common antibody detected was anti-NMDAR type followed by anti-LGI 1. Most common metabolic pattern in NMDARE was hypermetabolism in basal ganglia and hypometabolism in parieto-occipital cortices and ovarian teratoma was detected in two of these patients on whole-body PET. A metabolic pattern consistent with AIE was demonstrated in 22/29 (75.8%) antibody-negative patients with hypermetabolism in basal ganglia and mesial temporal cortices. The overall sensitivity of FDG PET was 86% (45/52). MRI abnormalities were detected in 22/52 (42%) cases, 10/23 antibody positive and 12/29 antibody negative cases. PET was positive in 23/30 (76%) MRI negative cases. CONCLUSION: Sensitivity of FDG PET for supporting a diagnosis of AIE was higher compared to MRI in both antibody-positive (definitive) and antibody-negative (presumed) AIE. Specific metabolic patterns can be demonstrated on FDG PET in AIE, prompting an early diagnosis so that timely treatment can be instituted.

Utility of Simple and Non-Invasive Strategies Alternative to Inferior Petrosal Sinus Sampling and Peripheral CRH Stimulation in Differential Diagnosis of ACTH-Dependent Cushing Syndrome.

We aimed to evaluate the utility of simple, cost-effective, and non-invasive strategies alternative to BIPSS and peripheral CRH stimulation in differential diagnosis of ACTH-dependent CS. First, we performed ROC analysis to evaluate the performance of various tests for differential diagnosis of ACTH-dependent CS in our cohort (CD, n=76 and EAS, n=23) and derived their optimal cut-offs. Subsequently, combining various demographic (gender), clinical (hypokalemia), biochemical (plasma ACTH, HDDST, peripheral CRH stimulation) and imaging (MRI pituitary) parameters, we derived non-invasive models with 100% PPV for CD. Patients with pituitary macroadenoma (n=14) were excluded from the analysis involving non-invasive models. Relative percent ACTH (AUC: 0.933) and cortisol (AUC: 0.975) increase on peripheral CRH stimulation demonstrated excellent accuracy in discriminating CD from EAS. Best cut-offs for CD were plasma ACTH<97.3 pg/ml, HDDST≥57% cortisol suppression, CRH stimulation≥77% ACTH increase and≥11% cortisol increase. We derived six models that provided 100% PPV for CD and precluded the need for BIPPS in 35/85 (41.2%) patients with ACTH-dependent CS and no macroadenoma (in whom BIPSS would have otherwise been recommended). The first three models included basic parameters and avoided both peripheral CRH stimulation and BIPSS in 19 (22.4%) patients, while the next three models included peripheral CRH stimulation and avoided BIPSS in another 16 (18.8%) patients. Using simple and non-invasive alternative strategies, BIPSS can be avoided in 41% and peripheral CRH stimulation in 22% of patients with ACTH-dependent CS and no macroadenoma; such patients can be directly referred for a pituitary surgery.

99mTechnetium-Ubiquicidin Scan with Single-Photon Emission Computed Tomography/Computed Tomography in Skull Base Osteomyelitis.

Malignant otitis externa (MOE) with skull base osteomyelitis (SBO) is an aggressive infection that predominantly affects elderly, diabetic, or immunocompromised patients, and is associated with high disease-specific mortality. Pseudomonas aeruginosa is the most isolated microorganism. External otitis associated with granulation tissue and pain is the most common presenting feature; a biopsy is obtained to rule out malignancy. A proper consensus is lacking regarding the best imaging modality for early initial diagnosis and follow-up. 99mTechnetium (99mTc)-labeled ubiquicidin (UBI) 29-41 is a bacterial attaching peptide that does not bind to activated leukocytes. We report a case of SBO initially misdiagnosed as a chronic otitis media, but later proved to be a case of MOE. 99mTc methylene diphosphonate bone scan and 99mTc-UBI 29-41 scan with single-photon emission computed tomography/computed tomography scans were performed to corroborate the clinical diagnosis. SBO remains a great challenge due to its increasing prevalence and high morbidity are difficult to diagnose and are often confused with cholesteatoma and neoplastic process. The UBI scan could be an auxiliary noninvasive diagnostic alternative in early diagnosis.

Comparison of Neck Ultrasonography, Dual Phase 99mTc-Sestamibi with early SPECT-CT & 18F-Fluorocholine PET-CT as First Line Imaging in Patients with Primary Hyperparathyroidism.

Introduction: Successful surgical treatment for primary hyperparathyroidism requires accurate localization of abnormal parathyroid tissue in terms of location and number. Imaging is important for localizing the parathyroid adenoma, and there has been significant interest in 18F-fluorocholine (FCH) positron emission tomography/computed tomography (PET/CT) for this purpose. Aim: This study attempted to ascertain the utility of 18F-FCH PET/CT as a first-line investigation in preoperative localization of abnormal parathyroid tissue in primary hyperparathyroidism, in comparison with 99mTc-sestamibi dual-phase scintigraphy with early single-photon emission computed tomography (SPECT)/CT and neck ultrasonography. Materials and Methods: Fifty-five patients with biochemical features of primary hyperparathyroidism were enrolled in this study. They underwent neck ultrasonography, 99mTc-sestamibi dual-phase scintigraphy with early SPECT/CT, and 18F-FCH PET/CT for localization of parathyroid lesions. Thirty-three patients underwent surgical resection of the detected lesions. For two patients, clinical and biochemical follow-up was used as a gold standard. Results: A total of 40 lesions were resected in the 33 patients who underwent surgery. A further two lesions were localized in two patients with clinical and biochemical follow-up as the gold standard. Of these 42 lesions, 41 were detected in preoperative imaging and 1 lesion was noted intraoperatively and resected. 41/42 lesions were detected by 18F-FCH PET/CT (detection rate: 97.6%), 33/42 by 99mTc-sestamibi dual-phase scintigraphy with early SPECT/CT (detection rate: 78.5%), and 30/42 by neck ultrasonography (detection rate: 71.4%). Conclusion: Detection rates on 18F-FCH PET/CT were superior to both 99mTc-sestamibi dual-phase scintigraphy with early SPECT/CT and neck ultrasonography in preoperative localization of parathyroid lesions in patients with primary hyperparathyroidism.

Macrofollicular Architecture in Invasive Encapsulated Follicular Variant of Papillary Thyroid Carcinoma: A Pitfall in Thyroid Practice.

BACKGROUND: Predominantly macrofollicular architecture in invasive encapsulated follicular variant of papillary thyroid carcinoma (IEFVPTC-MF) is rare and often a cause of misinterpretation during pre-operative work-up and histopathology evaluation. We comprehensively evaluated the radiological, cytological, gross, microscopic, molecular and follow-up characteristics of four such cases, intending to increase its recognition and add our experience to the limited literature available. METHODS: All such histopathologically-proven cases of IEFVPTC-MF were retrieved from the departmental archives. The clinical details, thyroid ultrasound, cytology and thyroid scan findings were reviewed. Allele-specific PCR for BRAF p.V600E, KRAS, NRAS, and HRAS mutations, and FISH assays for ETV6::NTRK3 fusion and RET fusions were performed. RESULTS: There were four cases of IEFVPTC-MF diagnosed between 2021 and 2022, involving two males and two females. The median age at presentation was 27 years, and the duration of the disease was 1-10 years. Thyroid ultrasound was TR1 (benign; n = 1), TR2 (not suspicious; n = 2), or TR4 (moderately suspicious; n = 1). Cytology was categorized as nondiagnostic (n = 1), benign (n = 1), and atypia of undetermined significance (n = 1). The three nodules with available cytology smears showed abundant colloid. Cells were arranged as sheets/microfollicles/clusters. Nuclei were predominantly round with minimal/focal elongation, membrane irregularity, and cellular crowding. On gross examination, cut surfaces of the tumors showed variable amounts of colloid. The tumors were solid-cystic. Histopathology revealed partially encapsulated multinodular tumors. There were prominent pseudopapillae projecting into the lumina of macrofollicles. Nuclei were predominantly round with variable nuclear atypia, including chromatin clearing and multifocal presence of nuclear grooves. Pseudoinclusions were identified in two. Molecular analysis revealed NRAS codon 61 mutation and ETV6::NTRK3 fusion in one case each. Two patients had cervical lymph node and hematogenous metastases. Post-radio-active iodine, the response was structurally incomplete (n = 2), indeterminate (n = 1) and excellent (n = 1). CONCLUSIONS: Macrofollicular architecture in invasive encapsulated follicular variant of papillary thyroid carcinoma is a major pitfall in thyroid oncology practice. Long-standing disease, and ultrasonographic and cytological features that overlap with benign disease, often lead to underdiagnosis during pre-operative evaluation. As patients may consequently develop distant metastases and have inadequate treatment response, there is a need for more vigilant understanding of the spectrum of macrofollicular thyroid disease for accurate diagnosis. ETV6::NTRK3 or other fusions, when found, present opportunities for targeted therapy.

Long-term survival outcomes of salvage [225Ac]Ac-PSMA-617 targeted alpha therapy in patients with PSMA-expressing end-stage metastatic castration-resistant prostate cancer: a real-world study.

PURPOSE: Despite the existence of various treatment options, the prognosis for patients with metastatic castration-resistant prostate cancer (mCRPC) remains unfavorable. One potential therapeutic approach is the use of [225Ac]Ac-PSMA-617, a targeted alpha therapy (TAT) that administers alpha-particle radiation specifically to prostate cancer cells expressing PSMA. In this study, we report the long-term survival outcomes of this novel therapy in a series of patients with mCRPC who have exhausted all standard treatment options. METHODS: The study enrolled patients with mCRPC who had shown resistance to standard lines of therapies, including next-generation anti-androgen therapies and taxane-based chemotherapies. These eligible patients received treatment with [225Ac]Ac-PSMA-617 at 100-150 kBq/kg doses administered every 8 weeks. The primary objective of the study was to assess overall survival (OS), while secondary objectives included evaluating radiological progression-free survival (rPFS), monitoring serum prostate-specific antigen (PSA) levels as a measure of biochemical response, and assessing adverse events using the CTCAE v5.0 grading system. RESULTS: Among the 63 initially enrolled patients, a total of 56 patients who had completed at least two cycles of [225Ac]Ac-PSMA-617 were included in this study. The mean age was 67 years (range, 39-87) and patients received a total of 204 cycles of [225Ac]Ac-PSMA-617 TAT. 91% of patients exhibited any PSA decline, with 67.8% experiencing a decline of 50% or more. The median follow-up was of 22 months (range: 6-59 months). Imaging-based disease progression was observed in 68% of patients, and 66% of patients succumbed to the disease. The median OS was 15 months (95% CI: 10-19). In univariate analysis, factors such as lack of >50% PSA decline (P=0.031), Eastern Cooperative Oncology Group (ECOG) performance status of 2 or higher (P=0.048), and radiological progression (rPD) (P<0.001) were found to be predictors of poor OS. However, in multivariate analysis, only rPD emerged as an independent prognostic factor with a hazard ratio (HR) of 8.264 (95% CI: 1.429-16.497, P=0.004). The estimated median rPFS was 9 months (95% CI: 7-15). Moreover, patients who demonstrated any PSA decline had a median rPFS of 10 months compared to only 3 months in patients without any PSA decline (multivariate HR: 6.749; 95% CI: 1.949-23.370; P=0.002). Fatigue was one of the most common treatment-emergent adverse events, with grades 1/2 occurring in 70% of patients and grades 3 or higher in 3.5% of patients. This fatigue was transient and resolved before the next treatment cycle. Additionally, approximately one-third of patients experienced xerostomia (grades 1/2: 32.1%). CONCLUSION: [225Ac]Ac-PSMA-617 targeted alpha therapy, was found to be well-tolerated with acceptable adverse events and effective in the treatment of patients with end-stage mCRPC.

Tc-99 m Ubiquicidin Imaging in Orbital Aspergilloma: an Illustration.

Aspergillus infection is relatively rare disease, and we present a case of orbital aspergillus infection who presented with right orbital pain and swelling. Right orbital lesion was identified on CT, MRI, and PET-CT imaging followed by confirmation of aspergillus on histopathological examination. We demonstrate that Tc-99 m ubiquicidin scan can yield positive results in aspergillosis too, enabling its differentiation from non-infective pathologies.

Lincoln Sign in a Case of Primary Hyperparathyroidism on 18 F-Fluorocholine PET/CT.

ABSTRACT: Lincoln sign or black beard sign is one of the signs that have been classically described on bone scintigraphy in monostotic Paget disease, when mandible is involved. Extensive involvement of the mandible causes increased radiotracer uptake from one mandibular condyle to the other, resembling a black beard. We present the case of a 14-year-old girl with primary hyperparathyroidism who underwent an 18 F-fluorocholine PE/CT to locate the parathyroid adenoma. MIP image of the PET/CT incidentally showed black beard sign due to increased radiotracer uptake in the mandible.

Malignancy-Associated Sarcoid-Like Reaction in a Case of Triple-Negative Breast Cancer on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

We describe the case of a 54-year-old woman with triple-negative breast cancer whose baseline F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) showed hypermetabolic left breast primary, ipsilateral axillary lymphadenopathy, lung nodules, and mediastinal lymph nodes. Histopathological examination of tissue from mediastinal lymph nodes confirmed a diagnosis of sarcoid-like reaction. Chemotherapy may induce or cause a flare-up of malignancy-associated sarcoid-like reaction. However, in our patient's post-chemotherapy F-18 FDG PET/CT, there was reduction in size and uptake of the mediastinal lymph nodes along with partial response shown by the other lesions. We aim to describe this rare course of malignancy-associated sarcoid-like reaction and highlight the role of F-18 FDG PET-CT in such cases.

Extensive Metastatic Vascular Calcification in a Patient with Chronic Renal Failure and Tubercular Osteomyelitis as Seen on F-18 Fluorodeoxyglucose Positron Emission Tomography/Computed Tomography.

A 48-year-old male with known tubercular osteomyelitis of the left elbow and chronic renal failure presented with PTH independent hypercalcemia and underwent F-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) to look for any underlying malignancy that might be causing his hypercalcemia. The PET/CT did not reveal any malignancy, but extensive metastatic calcification of small- and medium-sized arteries was noted throughout the body with relative sparing of large vessels. Alkaline tissue such as lungs, gastric mucosa, and kidneys that are usually involved in metastatic calcification were also spared. The underlying pathology for this kind of metastatic calcification was most likely chronic granulomatous disease, which was tubercular osteomyelitis in this patient. We present the PET/CT scan images of this unusual case of metastatic vascular calcification.

Imaging characteristics of phosphaturic mesenchymal tumors.

BACKGROUND: Tumor-induced osteomalacia (TIO) is a rare paraneoplastic syndrome associated with phosphaturic mesenchymal tumors (PMTs). Localization of the causative tumor in these cases is an arduous task since the culprit lesions are usually small, slow-growing, and can be located almost anywhere from head to toe. PURPOSE: To describe the morphological characteristics of histologically proven PMTs on various radiological modalities. MATERIAL AND METHODS: After institutional ethical approval, this retrospective study analyzed 20 cases with a histopathological evidence of PMT. Various imaging characteristics of the tumors on available computed tomography (CT) and magnetic resonance imaging (MRI) scans were evaluated. Descriptive statistical analyses were conducted. RESULTS: The tumors were located in diverse locations: lower extremities (n = 10); head and neck (n = 5); vertebral column (n = 3); pelvis (n = 1); and upper extremities (n = 1). Bone lesions seen on CT had variable morphology: sclerotic (n = 3/8, 37.5%); lytic (n = 3/8, 37.5%), and both lytic and sclerotic (n = 2/8, 25%) with presence of narrow zone of transition in all cases (n = 8/8) and amorphous internal matrix calcifications in 25% of cases (n = 2/8). Of the tumors, 68.4% (n = 13/19) were hypointense on T1 and all of them showed hyperintense signal on T2-weighted and STIR images (n = 19/19) and contrast enhancement (n = 16/16). Of the tumors, 66.7% (n = 6/9) showed restricted diffusion. DOTANOC PET/CT showed tumor uptake in all cases (n = 8/8). CONCLUSION: PMTs may have variable and non-specific tumor appearances on various imaging modalities. However, in an appropriate clinical scenario and a background of suggestive biochemical work-up, the radiologist should keep a high index of suspicion.

Clinical profile and treatment outcomes of patients with ectopic ACTH syndrome compared to Cushing disease: a single-center experience.

PURPOSE: We aimed to evaluate and compare the clinical, biochemical and radiological profile and outcomes of patients with ectopic ACTH syndrome (EAS) and Cushing disease (CD) treated over a period of 10 years (2013-2022). METHODS: In this ambispective observational study, we collected data for 146 patients with ACTH-dependent CS (EAS, n = 23; CD, n = 94; occult ACTH source, n = 29). Relevant details were filled in a predesigned proforma and outcomes were ascertained at the most recent visit. RESULTS: EAS was more common in males (65.2 vs. 27.6%, p < 0.001). Patients with EAS had a shorter duration of symptoms [12 (6-12) vs. 31.5 (15-48) months, p < 0.001] and were more likely to have hypokalemia (82.6 vs. 21.0%, p = 0.001), pedal edema (65.2 vs. 34.2%, p = 0.015), weight loss (34.8 vs. 4.0%, p < 0.001) and systemic infection (30.4 vs. 6.5%, p = 0.006). They also had significantly higher 8 a.m. serum cortisol, midnight serum and salivary cortisol and 8 a.m. plasma ACTH levels. Bronchial carcinoid (n = 10, 43.5%) was the most common etiology of EAS. Bilateral adrenalectomy was performed in 11 (47.8%) patients with EAS. Eight patients (34.8%) with EAS died at the last follow-up, of whom 7 (87.5%) had metastatic disease. In CD group, overall remission rate was 69.4% (56.1%, early and 13.3%, delayed) and 26.3% of patients with an initial remission had recurrence. CONCLUSIONS: Bronchial carcinoid was the most common cause of EAS in our cohort. Bilateral adrenalectomy was performed in approximately every 1 in 2 patients with EAS and approximately every 1 in 3 patients expired till the last follow-up.

Impact of Fluoro-Choline PET/CT in Reduction in Failed Parathyroid Localization in Primary Hyperparathyroidism.

INTRODUCTION: Accurate localization of the pathological parathyroid gland is a prerequisite for minimally invasive surgical management of hyperparathyroidism (HPT). Poor imaging or discordance in odd situations like ectopic adenomas, parathyroid hyperplasia, syndromic HPT results in localization dilemma thus causing failed parathyroidectomy. We studied the impact of Fluoro-Choline (FCH) PET/CT imaging in reduction in localization failure of parathyroid adenoma. MATERIALS AND METHODS: We did a retrospective observational study (2018-2021) of HPT among which 97 patients underwent focused parathyroidectomy (FP). All patients had undergone ultrasound imaging and 99mTc-sestaMIBI scan with early SPECT/CT (MIBI). When this preliminary imaging was doubtful or negative or multiple lesions were expected, FCH PET/CT was performed. We compared the localization accuracy of MIBI scan and FCH PET/CT with surgical outcomes as reference standard. RESULTS: MIBI scan showed overall lesion detection rate (LDR) of 88.65% in localization of pathological parathyroid gland in 97 patients. The addition of FCH PET/CT improved the overall lesion detection to 97.9%. The overall possible localization failure was reduced from 11.34 to 2.06% with the addition of FCH PET/CT (p < 0.05). Out of 97 patients of FP, 87 patients showed features of parathyroid adenoma. Single hyperplastic gland was seen in 7 patients, lipoadenoma was seen in 1 patient and 1 patient had features suggestive of parathyroiditis on histopathology. FCH PET/CT was a useful adjunct and showed significant reduction in localization failure of parathyroid adenoma.