Dual-Phase 99mTc-MIBI SPECT/CT in the Characterization of Enhancing Solid Renal Tumors: A Single-Institution Study of 147 Cases

Juxtaglomerular Cell Tumor Mimicking Renal Cell Carcinoma on 99m Tc-MIBI SPECT/CT

ABSTRACT

Juxtaglomerular cell tumor or reninoma is an extremely rare, typically benign, renin-secreting tumor of the kidney that causes secondary hypertension. We describe 99m Tc-MIBI SPECT/CT findings in a case of juxtaglomerular cell tumor. The renal tumor showed isodensity and photopenia on 99m Tc-MIBI SPECT/CT. This case indicates that juxtaglomerular cell tumor can appear cold on 99m Tc-MIBI SPECT/CT, mimicking renal cell carcinoma.

The Role of 99mTc-Sestamibi Single-photon Emission Computed Tomography/Computed Tomography in the Diagnostic Pathway for Renal Masses: A Systematic Review and Meta-analysis

CONTEXT

The diagnostic accuracy of current imaging techniques in differentiating benign from malignant neoplasms in the case of indeterminate renal masses is still suboptimal.

OBJECTIVE

To evaluate the diagnostic accuracy of 99mTc-sestamibi (SestaMIBI) single-photon emission tomography computed tomography (SPECT)/CT in characterizing indeterminate renal masses by differentiating renal oncocytoma and hybrid oncocytic/chromophobe tumor (HOCT) from (1) all other renal lesions and (2) all malignant renal lesions. Secondary outcomes were: (1) benign versus malignant; (2) renal oncocytoma and HOCT versus clear cell (ccRCC) and papillary (pRCC) renal cell carcinoma; and (3) renal oncocytoma and HOCT versus chromophobe renal cell carcinoma (chRCC).

EVIDENCE ACQUISITION

A literature search was conducted up to November 2022 using the PubMed/MEDLINE, Embase, and Web of Science databases. Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to identify eligible studies. Studies included were prospective and retrospective cross-sectional studies in which SestaMIBI SPECT/CT findings were compared to histology after renal mass biopsy or surgery.

EVIDENCE SYNTHESIS

Overall, eight studies involving 489 patients with 501 renal masses met our inclusion criteria. The sensitivity and specificity of SestaMIBI SPECT/CT for renal oncocytoma and HOCT versus all other renal lesions were 89% (95% confidence interval [CI] 70-97%) and 89% (95% CI 86-92%), respectively. Notably, for renal oncocytoma and HOCT versus ccRCC and pRCC, SestaMIBI SPECT/CT showed specificity of 98% (95% CI 91-100%) and similar sensitivity. Owing to the relatively high risk of bias and the presence of heterogeneity among the studies included, the level of evidence is still low.

CONCLUSIONS

SestaMIBI SPECT/CT has good sensitivity and specificity in differentiating renal oncocytoma and HOCT from all other renal lesions, and in particular from those with more aggressive oncological behavior. Although these results are promising, further studies are needed to support the use of SestaMIBI SPECT/CT outside research trials.

PATIENT SUMMARY

A scan method called SestaMIBI SPECT/CT has promise for diagnosing whether kidney tumors are malignant or not. However, it should still be limited to research trials because the level of evidence from our review is low.

99mTc-MIBI SPECT/CT in a Case of Renal Oncocytosis

ABSTRACT

Renal oncocytosis is a very rare oncologically indolent form of renal neoplasia characterized by diffuse involvement of renal parenchyma by numerous oncocytic nodules. We describe contrast-enhanced CT and 99mTc-MIBI SPECT/CT findings in a patient with renal oncocytosis presenting with metachronous bilateral renal tumors. Contrast-enhanced CT showed numerous tumors ranging from several millimeters up to 3.9 cm in the left kidney. The tumors showed hypervascularity in the corticomedullary phase and washout in the excretory phase mimicking renal cell carcinoma. The larger tumors showed higher 99mTc-MIBI uptake than the adjacent renal parenchyma, suggesting renal oncocytoma confirmed by biopsy.

Molecular Imaging Diagnosis of Renal Cancer Using 99mTc-Sestamibi SPECT/CT and Girentuximab PET-CT-Current Evidence and Future Development of Novel Techniques

Novel molecular imaging opportunities to preoperatively diagnose renal cell carcinoma is under development and will add more value in limiting the postoperative renal function loss and morbidity. We aimed to comprehensively review the research on single photon emission computed tomography/computed tomography (SPECT/CT) and positron emission tomography computed tomography (PET-CT) molecular imaging and to enhance the urologists' and radiologists' knowledge of the current research pattern. We identified an increase in prospective and also retrospective studies that researched to distinguish between benign and malignant lesions and between different clear cell renal cell carcinoma subtypes, with small numbers of patients studied, nonetheless with excellent results on specificity, sensitivity and accuracy, especially for ^99mTc-sestamibi SPECT/CT that delivers quick results compared to a long acquisition time for girentuximab PET-CT, which instead gives better image quality. Nuclear medicine has helped clinicians in evaluating primary and secondary lesions, and has lately returned with new and exciting insights with novel radiotracers to reinforce its diagnostic potential in renal carcinoma. To further limit the renal function loss and post-surgery morbidity, future research is mandatory to validate the results and to clinically implement the diagnostic techniques in the context of precision medicine.

Diagnostic Accuracy of 99mTc-Sestamibi SPECT/CT for Characterization of Solid Renal Masses

Our objective was to assess the diagnostic accuracy of ^99mTc-sestamibi SPECT/CT for characterizing solid renal masses. Methods: Imaging and clinical records of patients who underwent ^99mTc-sestamibi SPECT/CT for clinical work-up of their solid renal masses from September 2018 to October 2021 were retrospectively reviewed. Histopathology formed the reference standard, and the diagnoses were categorized as malignant/concerning (renal cell carcinomas [RCCs] other than chromophobe histology) and benign/nonconcerning (oncocytic tumors including chromophobe RCC, other benign diagnoses) to calculate the sensitivity and specificity of ^99mTc-sestamibi SPECT/CT and contrast-enhanced CT (ceCT). The clinical reads of the SPECT/CT images were used for visual classification of the lesions. Additionally, the SPECT images were manually segmented to obtain the maximum and mean counts of the lesion and adjacent renal cortex and maximum and mean lesion Hounsfield units. Results: ^99mTc-sestamibi SPECT/CT was performed on 42 patients with 62 renal masses. A histopathologic diagnosis was available for 27 patients (18 male, 9 female) with 36 solid renal masses. ceCT findings were available for 20 of these patients. The most commonly identified single histologic type was clear cell RCC (13/36; 36.1%). Oncocytic tumors were the most common group of nonconcerning lesions (15/36), with oncocytoma as the predominant histologic type (n = 6). The sensitivity and specificity of SPECT/CT for diagnosing a nonconcerning lesion were 66.7% and 89.5%, respectively, compared with 10% and 75%, respectively, for ceCT. The lesion-to-kidney ratios for maximum and mean counts and maximum lesion Hounsfield units showed significant differences between the 2 groups (P < 0.05). The lesion-to-kidney mean count ratio at a cutoff of 0.46 showed a sensitivity and specificity of 87.5% and 86.67%, respectively, for detecting nonconcerning lesions, which was significantly higher than that of ceCT. Conclusion: The current literature on the utility of ^99mTc-sestamibi SPECT/CT for characterization of solid renal masses is limited. We offer additional evidence of the incremental value of ^99mTc-sestamibi SPECT/CT over ceCT for differentiating malignant or aggressive renal tumors from benign or indolent ones, thereby potentially avoiding overtreatment and its associated complications. Quantitative assessment can further increase the diagnostic accuracy of SPECT/CT and may be used in conjunction with visual interpretation.

FDG PET/CT in Eosinophilic Solid and Cystic Renal Cell Carcinoma With Lung Metastases

ABSTRACT

Eosinophilic solid and cystic renal cell carcinoma is a recently described emerging renal tumor. Usefulness of FDG PET/CT in the management of eosinophilic solid and cystic renal cell carcinoma has been rarely reported. We describe FDG PET/CT findings in a case of eosinophilic solid and cystic renal cell carcinoma with lung metastases. The primary renal tumor and its metastases showed intense FDG uptake with SUV max of 29.3 for the primary tumor and 21 for the lung metastases.

Super Early Scan of PSMA PET/CT in Evaluating Primary and Metastatic Lesions of Prostate Cancer

68Ga-prostate specific membrane antigen (PSMA)-11 PET/CT has been widely used in the diagnosis of prostate cancer (PCa); however, the urine lead shielding resulting from the urinary metabolism of tracers may obstruct the detection of surrounding metastasis. In this research, the additive value of super early scanning in diagnosing primary lesions and metastasis in the pelvic cavity was evaluated. Firstly, the differentiation efficiency of 68Ga-PSMA-11 PET scanned at 3 min post-injection (min P.I.) was measured in PSMA-positive (22rv1 cells) and PSMA-negative (PC3 cells) model mice. Secondly, 106 patients were scanned at 3 min P.I. for the pelvic cavity and then scanned as a standard protocol at 45 min P.I. In the results, the differential diagnosis of PSMA expression was completely reflected as early as 3 min P.I. for mice models. For patients, when correlated with the Gleason score, the quantitative results of the super early scan displayed a comparable correlation coefficient with the routine scan. The target to bladder ratios increased from 1.44 ± 2.40 at 45 min to 10.10 ± 19.10 at 3 min (p < 0.001) for the primary lesions, and it increased from 0.99 ± 1.88 to 9.27 ± 23.03 for metastasis. Meanwhile, the target to background ratios increased from 2.21 ± 2.44 at 3 min to 19.13 ± 23.93 at 45 min (p < 0.001) for the primary lesions, and it increased from 1.68 ± 2.71 to 12.04 ± 18.73 (p < 0.001) for metastasis. In conclusion, super early scanning of 68Ga-PSMA-11 PET/CT added referable information for metastasis detection in order to avoid disturbing tracer activity in the urinary system.

99m Tc sestamibi SPECT/CT in the prediction of malignant versus benign small renal masses

OBJECTIVES

To determine the effectiveness of ^99m Tc-sestamibi renal SPECT/CT in distinguishing between malignant and benign renal lesions.

PATIENTS AND METHODS

Between June 2018 and October 2020 all patients with new indeterminate small renal masses (SRMs) underwent ^99m Tc-sestamibi renal SPECT/CT prior to biopsy or surgery. The accuracy of ^99m Tc-sestamibi imaging diagnoses was assessed against histopathology. Receiver operating characteristic (ROC) analysis was used to determine the optimum cut-off for the tumour:normal uptake ratio. Logistic regression was used to determine if quantitative analysis significantly added to visual interpretation alone.

RESULTS

A total of 74 patients with SRMs were investigated with ^99m Tc-sestamibi SPECT/CT. SPECT/CT correctly identified 49 malignant tumours and 11 benign tumours, resulting in a sensitivity of 0.89 [95% CI: 0.77 - 0.95] and a specificity of 0.73 [95% CI: 0.45 - 0.91]. ROC analysis of uptake ratios demonstrated that a tumour:normal uptake ratio of 0.41 provided optimal diagnostic accuracy (sensitivity 0.81, specificity 0.88, area under the curve 0.883 [95% CI:0.794 - 0.971]). The uptake ratio was also highly significant in excluding malignancy on univariate logistic regression analysis whereby the higher the uptake ratio, the lower the chances were for malignancy (OR 0.009,95% CI: 0.001-0.118, p < 0.001. However, this did not improve diagnostic accuracy when compared to visual interpretation alone.

CONCLUSION

^99m Tc-sestamibi SPECT/CT is a non-invasive technique with good accuracy in determining if a SRM is benign or malignant.

Renal Oncocytoma: The Diagnostic Challenge to Unmask the Double of Renal Cancer

Renal oncocytoma represents the most common type of benign neoplasm that is an increasing concern for urologists, oncologists, and nephrologists due to its difficult differential diagnosis and frequent overtreatment. It displays a variable neoplastic parenchymal and stromal architecture, and the defining cellular element is a large polygonal, granular, eosinophilic, mitochondria-rich cell known as an oncocyte. The real challenge in the oncocytoma treatment algorithm is related to the misdiagnosis due to its resemblance, at an initial radiological assessment, to malignant renal cancers with a completely different prognosis and medical treatment. Unfortunately, percutaneous renal biopsy is not frequently performed due to the possible side effects related to the procedure. Therefore, the majority of oncocytoma are diagnosed after the surgical operation via partial or radical nephrectomy. For this reason, new reliable strategies to solve this issue are needed. In our review, we will discuss the clinical implications of renal oncocytoma in daily clinical practice with a particular focus on the medical diagnosis and treatment and on the potential of novel promising molecular biomarkers such as circulating microRNAs to distinguish between a benign and a malignant lesion.

99mTc-MIBI SPECT/CT and FDG PET/CT in Isolated Bilateral Renal Metastases From Adenoid Cystic Carcinoma of the Maxilla

ABSTRACT

Renal metastasis from adenoid cystic carcinoma of the head and neck is uncommon. We present 99mTc-MIBI SPECT/CT and FDG PET/CT findings in a case with isolated bilateral renal metastases from adenoid cystic carcinoma of the left maxilla. The metastatic adenoid cystic carcinomas of the kidneys showed photopenia on 99mTc-MIBI SPECT/CT and increased FDG uptake on FDG PET/CT mimicking primary renal cell carcinoma.

Metanephric Adenoma Mimicking Renal Cell Carcinoma on 99mTc-MIBI SPECT/CT

ABSTRACT

Metanephric adenoma is a rare benign renal tumor. A 49-year-old woman presented with a left renal pelvic mass detected by ultrasound. Enhanced CT of the kidney showed slight enhancement of the mass. For characterization of the mass, 99mTc-MIBI SPECT/CT was performed showing photopenia of the mass. Renal cell carcinoma was suspected. The mass was removed surgically. Metanephric adenoma was confirmed by histopathology. This case indicates that metanephric adenoma can appear cold on 99mTc-MIBI SPECT/CT, mimicking renal cell carcinoma.

Parotid Oncocytoma on 99mTc-Sestamibi Scintigraphy and SPECT/CT

ABSTRACT

Oncocytomas in the parotid gland are a rare benign neoplasm composed of mitochondrial-rich oncocytes. Here we present the case of an 85-year-old man with a history of biopsy-proven right parotid gland oncocytoma who underwent 99mTc-sestamibi scintigraphy and SPECT/CT in the context of primary hyperparathyroidism. Focal intense uptake of radiotracer is detected within the right parotid gland on sestamibi scintigraphy. SPECT/CT confirms the localization of sestamibi uptake to the hyperattenuating parotid gland oncocytoma.