Extracranial Meningioma-Pelvic Bone on FDG PET/CT: A Rare of the Rarest Site

ABSTRACT

Meningiomas are benign extra-axial tumors of the central nervous system. Extracranial meningiomas are extremely rare (2%) and can develop as a direct extension from a primary intracranial meningioma or as a true primary extracranial meningioma originating from ectopic arachnoid cells. We report an extremely unusual case of a 61-year-old woman who was diagnosed with pelvic meningioma with the help of PET/CT and PET/CT-guided biopsy. The clinicopathological features of the patient and immunoprofile of the tumor are presented.

PSMA Avidity in the Heterotropic Ossification-An Incidental Finding on PSMA PET/CT

ABSTRACT

The upregulations of prostate-specific membrane antigen (PSMA) antigen are used for the presence of prostate cancer. However, published literature shows incidentally detected PSMA uptake in various nonprostatic benign and malignant conditions, which led to questioning the specificity of PSMA-targeted PET. In present case, we highlighted the abnormal PSMA expression in the benign bone abnormality.

FDG PET-CT in Clinical Management of a Rare Case of Primary Hepatic Lymphoma: Role and Challenges

The common differential diagnoses for multiple space-occupying hepatic lesions (SOL) are metastases, multifocal hepatocellular carcinoma, and abscess. Primary hepatic lymphomas are rare entities that present many challenges with regard to their management. Fluorodeoxyglucose positron emission tomography-computed tomography is extensively used for the staging and response assessment of lymphomas but it can be challenging and difficult to interpret in cases with isolated liver involvement. We hereby present the case of an 82-year-old lady who presented with multiple liver SOL.

Follicular Thyroid Carcinoma with Unusual Radioiodine-Refractory Breast Metastasis Mimicking Primary Breast Malignancy

The breast is an unusual site for metastasis from malignant tumors, although it may be the first manifestation of an extramammary primary malignancy typically arising in the lung, skin (melanoma), ovary, or lymph nodes (lymphoma). Breast metastasis from thyroid carcinoma is extremely rare and may take years to develop, as differentiated thyroid carcinoma is usually indolent and slow-growing and metastasizes to the lymph nodes, lungs, and bones. Here, we present the case of a middle-aged woman (after subtotal thyroidectomy for multinodular goiter 24 y previously) showing discordant ¹⁸F-FDG and iodine avidity in proven metastatic disease involving the lymph nodes, bones, spleen, and breast on whole-body ¹³¹I and ¹⁸F-FDG scans due to tumor heterogeneity.

Should fluorodeoxyglucose positron emission tomography/computed tomography be the first-line imaging investigation for restaging the laryngeal carcinoma patients?

Posttreatment detection of residual/recurrence disease in the head and neck cancers is not an easy task. Treatment induces changes create difficulties in diagnosis on conventional imaging (computed tomography [CT], magnetic resonance imaging) as well as macroscopic inspection (direct laryngoscopy). Hence, we evaluate the diagnostic performance of contract-enhanced F-18 fluorodeoxyglucose positron emission tomography (FDG PET)/CT in restaging of laryngeal carcinoma Postchemotherapy-surgery and/or radiation therapy. We retrospectively analyzed patients of carcinoma larynx (n = 100) who has completed treatment and were referred for FDG PET/CT. Two reviewers performed image analysis to determine recurrence at primary site and/lymph nodes and distant metastases. Receiver operating characteristic (ROC) was used to determine the maximum standardized uptake value (SUV_max) cut off for disease detection. Histopathological examination and clinical or imaging follow-up were taken as gold standard for recurrence. One hundred laryngeal carcinoma patients with mean age of 57.2 years (range of 40–76) were included in the present study. Among the 100 patients, 96 were male and remaining 4 were female. The average interval between completion of treatment and FDG PET/CT scan was 8.5 months (minimum 6 months). Of the 100 patients, FDG PET/CT detected FDG avid lesions in 66 patients. Sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of FDG PET/CT for residual/recurrence disease detection was 90.3%, 73.7%, 84.8%, 82.3%, and 84.0%, respectively (P < 0.05). In addition, in 10 patients, metachronous primaries were detected (lung-4, thyroid-2, tongue, colon, esophagus, and lymphoma-one each). On ROC curve analysis, SUVmax >6.1 had sensitivity and specificity of 80.6% and 94.7% respectively for detection of recurrent/metastatic disease. FDG PET/CT demonstrates high diagnostic accuracy for detection of residual/recurrent disease in treated laryngeal cancer patients and our findings suggest that this imaging modality should be the first-line diagnostic investigation in this cohort of patients.

Isolated Malignant Portal Vein Thrombus in Colon Carcinoma: A Rare Finding on 18F-FDG PET/CECT

In the absence of hepatic metastasis in abdominal cancers, an isolated malignant portal vein thrombus is very rare. The presence of a malignant thrombus has clinical significance for determining the stage, treatment, and prognosis. ¹⁸F-FDG PET/CECT is a noninvasive modality for discriminating between malignant and benign thrombi. We present a case of primary sigmoid colon carcinoma for which ¹⁸F-FDG PET/CT showed, in addition to the ¹⁸F-FDG-avid primary lesion, an ¹⁸F-FDG-avid filling defect in the portal vein, likely malignant thrombus.

Real Time F-18 FDG PET-CT-Guided Metabolic Biopsy Targeting Differential FDG Avidity in a Pulmonary Blastoma

Pulmonary blastoma (PB) is a rare thoracic malignancy and preoperative diagnosis is challenging. A young man presented with dyspnea and chest pain for 3-4 months and chest-computed tomography (CT) revealed large mass in the left lung upper lobe and pleural effusion. Repeated CT-guided fine-needle aspiration cytology from the lesion and pleural fluid aspiration was negative for malignancy. F-18-fluorodeoxyglucose positron emission tomography-computed tomography (FDG PET-CT) revealed heterogeneous tracer avidity in left lung mass with areas of necrosis. Real-time PET-CT-guided biopsy from metabolically active component of the lesion revealed biphasic PB on histopathology.

A rare adult renal neuroblastoma better imaged by 18F-FDG than by 68Ga-dotanoc in the PET/CT scan

Primary renal neuroblastoma is an uncommon tumor in children and extremely rare in adults. We present a case of a middle aged female having a large retroperitoneal mass involving the right kidney with features of neuroblastoma on pre-operative histopathology. Whole-body fluorine-18-fluoro-deoxyglucose positron emission tomography (¹⁸F-FDG PET/CT) and ⁶⁸Ga-dotanoc PET/CT scans performed for staging and therapeutic potential revealed a tracer avid mass replacing the right kidney and also pelvic lymph nodes. The ¹⁸F-FDG PET/CT scan showed better both the primary lesion and the metastases in the pelvic lymph nodes than the ⁶⁸Ga-dotanoc scan supporting diagnosis and treatment planning.

Disseminated Skeletal Muscle and Cardiac Metastasis from Squamous Cell Carcinoma of the Lung Detected with FDG and FLT PET/CT

Lung cancer is one of the leading cancers all over the world. Positron emission tomography (PET) using 18F fluorodeoxyglucose (18F FDG) is useful for staging of the disease and decide the appropriate management. 3’-deoxy-3’-18 F-fluorothymidine (18F FLT) is a tracer being extensively evaluated currently and is said to represent tumor proliferation. Common sites of metastases from lung cancer include adrenal glands, bone, and brain. Muscle metastasis and cardiac metastasis are uncommon findings. We report a case of squamous cell carcinoma of the lung with metastases to multiple skeletal muscles and myocardium detected with both FDG and FLT PET/computed tomography (CT).

Unusual Presentation of Bladder Paraganglioma: Comparison of (131)I MIBG SPECT/CT and (68)Ga DOTANOC PET/CT

Extraadrenal chromaffin cell-related tumors or paragangliomas are rare, especially in the bladder, accounting for less than 1% of cases. We report a 16-year-old boy who presented with hematuria and paroxysmal headache and was found to have a prostatic growth infiltrating the urinary bladder on anatomical imaging. Iodine-131 ((131)I) metaiodobenzylguanidine (MIBG) whole-body scanning and subsequently gallium-68 ((68)Ga) DOTANOC positron emission tomography/computed tomography (PET/CT) were performed. The MIBG scan revealed a non-tracer-avid soft-tissue mass, while DOTANOC PET/CT revealed a tracer-avid primary soft-tissue mass involving the urinary bladder and prostate with metastasis to the iliac lymph nodes. He underwent surgical management; histopathology of the surgical specimen revealed a bladder paraganglioma, whereas the prostate was found to be free of tumor.

Dual thyroid ectopia-role of thyroid scintigraphy and neck ultrasonography

Ectopic thyroid tissue (ETT) is a rare developmental anomaly of the thyroid tissue where the thyroid gland is not located in its usual position. Dual thyroid ectopia is far rarer. This case of a 5-year-old euthyroid girl with thyroglossal cyst was planned for surgery. Presurgical ultrasonography (USG) of the neck followed by thyroid scintigraphy was performed. There was absent normal thyroid gland with single ETT in neck swelling on USG. However, thyroid scintigraphy revealed two ectopic foci of thyroid tissue; one was corresponding to neck swelling, and other was superior to it at the base of the tongue along with absent eutopic thyroid gland. The repeat neck USG could demonstrate the same. The present case emphasizes that, if the thyroid gland is not visible by USG; ETT should be evaluated with thyroid scintigraphy in case of thyroid dysgenesis.

Lung or liver: An imaging dilemma on Tc-99m macroaggregated albumin lung perfusion scintigraphy

We present a 10-year-old boy having the bronchiectasis who was subjected to lung perfusion scintigraphy before lung resection surgery to assess the lung parenchymal function. It revealed unusual tracer distribution in right upper body that was mimicking to be liver. It was unusual unless there were some shunts bypassing the lung uptake or faulty radiopharmaceutical preparation. However by bringing down the image window, it became clear that radiopharmaceutical distribution was in thorax only correlating with lung uptake, and not in the liver. Corresponding X-ray chest and computed tomography thorax demonstrated multiple cystic lesions in left lung parenchyma.

Vicarious liver visualization in solitary functioning kidney with technetium-99m ethylenedicysteine renal scintigraphy

We present a case of 3-year-old boy who was incidentally diagnosed to have single left kidney on ultrasonography. Dynamic technetium-99m ethylenedicysteine renal scintigraphy was acquired for assessing the existing kidney function showed the tracer localization in bilateral renal fossae during the entire study. The single-photon emission computerized tomography/computerized tomography study revealed activity in the right renal fossa to be in the enlarged right lobe of the liver, which was mimicking as impaired functioning right kidney in planar images. The hybrid imaging helped in accurate delineation of tracer uptake by confirming it to be the false appearance of the right kidney in planar imaging. This case report also highlights the possible mechanism of renal tracer uptake in the liver parenchyma.

Diagnostic dilemma of degenerative joint disease, chronic avascular necrosis or metastasis in planar Tc-99m-methylene diphosphonate planar skeletal scintigraphy excluded by single positron emission computed tomography/computed tomography

We present a 71-year-old male patient subjected to skeletal scintigraphy for metastasis work up of prostate cancer. Whole body planar images revealed a solitary focal tracer uptake in left femoral head mimicking as solitary metastatic focus. Single positron emission computed tomography/computed tomography images localized this increased tracer uptake to the subchondral cysts with minimal sclerosis in left femur head with no decrease in size of femur head and was reported as (degenerative joint disease).

Follow-up (99m)Tc EC renal dynamic scintigraphy and DMSA-III SPECT/CT in unmasking a masqueraded case of Horseshoe kidney

Hydronephrosis is a common finding in urinary tract outflow obstruction. Chronically obstructed hydronephrotic system may be associated with parenchymal changes. Ultrasound, intravenous urography, micturating cysto-urethrogram and scintigraphy are commonly performed to evaluate the cause of obstruction. In childhood, pelviureteric junction obstruction is a common cause of the hydronephrosis. Hydronephrosis can also be present in horseshoe kidneys due to poor drainage. However, a large sized hydronephrotic cavity may obscure the finding of horseshoe kidney. A case was reported, and it was diagnosed as horseshoe kidney on follow-up renal dynamic scan and confirmed with the help of dimercaptosuccinic acid SPECT/CT.

Diagnostic accuracy of integrated (18)F-FDG PET/CT for restaging patients with malignant germ cell tumours

OBJECTIVE

Evaluation of utility of fluorine-18 fludeoxyglucose ((18)F-FDG) positron emission tomography/CT (PET/CT) for restaging patients with primary malignant germ cell tumours (GCTs).

METHODS

Data of 92 patients (age, 31.94 ± 10.1 years; male/female, 86/6) with histopathologically confirmed malignant GCTs (gonadal, 88; mediastinal, 4; seminomatous, 47 and non-seminomatous, 45) who underwent (18)F-FDG PET/CT for restaging (suspected recurrence/post-therapy evaluation) were retrospectively analysed. Two experienced nuclear medicine physicians reviewed the PET/CT images in consensus, qualitatively and semi-quantitatively [maximum standardized uptake value (SUVmax)]. Histopathology (if available) and clinical/imaging/biochemical follow-up (minimum of 6 months) were employed as the reference standard.

RESULTS

(18)F-FDG PET/CT was interpreted as positive in 59 and negative in 33 patients. Local disease was seen in 5, nodal disease in 50 and distant metastasis in 22 patients. PET/CT was true positive in 49, false positive in 10, true negative in 30 and false negative in 3 patients. (18)F-FDG PET/CT showed sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 94.2%, 75.0%, 83.0%, 90.9% and 85.8% overall; 90.0%, 74.0%, 72.0%, 90.9% and 80.8% in seminomatous GCT; and 96.8%, 76.9%, 91.1%, 90.9% and 91.1% in non-seminomatous GCT, respectively. Difference in PET/CT accuracy for seminomatous and non-seminomatous GCTs was not significant (p = 0.263). PET/CT demonstrated disease in 13 patients with negative/equivocal conventional imaging findings and in 9 patients with normal tumour markers. No site- or histology-based difference was seen in SUVmax.

CONCLUSION

(18)F-FDG PET/CT demonstrates high diagnostic accuracy for restaging patients with malignant GCTs. It has comparable diagnostic performance in both seminomatous and non-seminomatous malignant GCTs.

ADVANCES IN KNOWLEDGE

The present article demonstrates high diagnostic accuracy of (18)F-FDG PET/CT for restaging both seminomatous and non-seminomatous malignant GCTs in a large patient population.

Carcinoma of unknown primary of neuroendocrine origin: Accurate detection of primary with (68)Ga-labelled [1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid]-1-NaI3-Octreotide positron emission tomography/computed tomography enterography

⁶⁸Ga-labelled [1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid]-1-NaI3-Octreotide (⁶⁸Ga-DOTANOC) positron emission tomography/computed tomography (PET/CT) is an excellent modality in patients with carcinoma of unknown primary of neuroendocrine origin. Most of the primary lesions are located in mid gut region where the lesions have poor resolution due to undistended and overlapping intestinal loops and motility-related artifacts. Although PET/CT enteroclysis, enterography and colonography have been described with ¹⁸F-fluorodeoxyglucose, PET/CT enterography with⁶⁸Ga-DOTANOC has not been described in the literature. Here, we present a case where⁶⁸Ga-DOTANOC PET/CT enterography was useful in identifying the primary neuroendocrine tumor lesion in small intestine with accurate delineation.

Comparison of single photon emission computed tomography-computed tomography, computed tomography, single photon emission computed tomography and planar scintigraphy for characterization of isolated skull lesions seen on bone scintigraphy in cancer patients

Purpose:

The purpose of this study is to evaluate the added value of single photon emission computed tomography-computed tomography (SPECT-CT) over planar scintigraphy, SPECT and CT alone for characterization of isolated skull lesions in bone scintigraphy (BS) in cancer patients.

Materials and Methods:

A total of 32 cancer patients (age: 39.5 ± 21.9; male: female - 1:1) with 36 isolated skull lesions on planar BS, underwent SPECT-CT of skull. Planar BS, SPECT, CT and SPECT-CT images were evaluated in separate sessions to minimize recall bias. A scoring scale of 1-5 was used, where 1 is definitely metastatic, 2 is probably metastatic, 3 is indeterminate, 4 is probably benign and 5 is definitely benign. With receiver operating characteristic analysis area under the curves (AUC) was calculated for each modality. For calculation of sensitivity, specificity and predictive values a Score ≤3 was taken as metastatic. Clinical/imaging follow-up and/or histopathology were taken as reference standard.

Results:

Of 36 skull lesions 11 lesions each were on frontal, parietal and occipital bone while three lesions were in the temporal bone. Of these 36 lesions, 16 were indeterminate (Score-3) on planar and SPECT, five on CT and none on SPECT-CT. The AUC was largest for SPECT-CT followed by CT, SPECT and planar scintigraphy, respectively. Planar scintigraphy was inferior to SPECT-CT (P = 0.006) and CT (P = 0.012) but not SPECT (P = 0.975). SPECT was also inferior to SPECT-CT (P = 0.007) and CT (P = 0.015). Although no significant difference was found between SPECT-CT and CT (P = 0.469), the former was more specific (100% vs. 94%).

Conclusion:

SPECT-CT is better than planar scintigraphy and SPECT alone for correctly characterizing isolated skull lesions on BS in cancer patients. It is more specific than CT, but provides no significant advantage over CT alone for this purpose.