Solitary Benign Schwannoma Mimics Residual Malignancy on FDG PET/CT

18F-FDG PET/CT of Benign Tracheal Schwannoma

ABSTRACT

Schwannoma is a benign tumor originating from Schwann cells. It commonly occurs in the head, neck, and extremities, but rarely occurs in the trachea. Tracheal schwannoma is usually asymptomatic. We reported the 18F-FDG PET/CT findings of a 61-year-old man with bronchoscopically biopsy-proven schwannoma, which presented challenges in differentiation from certain benign tumors and low-grade malignancies in the trachea.

Rare retroperitoneal giant sacral schwannoma: A case report

Schwannomas localized in the sacrum are relatively infrequent, accounting for 1-5% of all spinal axis schwannomas; they present with vague symptoms or are symptomless, so often grow to a considerable size before detection. Sacral schwannomas occasionally present with enormous dimensions, and these tumors are termed giant sacral schwannomas. However, their surgical removal is challenging owing to an abundant vascularity. The present study retrospectively analyzed the clinical and follow-up data of a patient with a giant sacral schwannoma. The patient experienced numbness in the left buttock and lower extremity, with radiating pain in the sole of the foot that had persisted for 3 years. A presacral mass was found by computed tomography examination 6 months after the stool had become thin. A tumor resection was performed using the anterior abdominal approach. A schwannoma was diagnosed by postoperative pathology. The postoperative course was uneventful, with the complete resolution of symptoms during the 21-month clinical follow-up. Overall, the present study reports the case of a giant sacral schwannoma with pelvic pain that was resected without complications and also discusses its successful management. Additionally, the study presents a systematic review of the literature. We consider that the surgical treatment of giant sacral schwannomas with piecemeal subtotal excision can achieve good outcomes, avoiding unnecessary neurological deficits.

Increased Genioglossus Muscle FDG Activity Due to Using Pacifier

ABSTRACT

An 18-month-old girl with history of liver transplant underwent FDG PET/CT to evaluate posttransplant lymphoproliferative disorder. In addition to multistation hypermetabolic lymphadenopathy and abnormal activity in the liver, stomach, and small bowel, in keeping with known posttransplant lymphoproliferative disorder, the images also showed focal activity in the submental region. This submental activity persisted on 2 separate follow-up FDG PET/CT studies, even though other foci of abnormal activity resolved after chemotherapy. Records revealed that the patient was sucking on a pacifier prior to all 3 FDG PET/CT studies, and the submental uptake corresponded with genioglossus muscle activity.

Pelvic Plexiform Schwannoma on 18F-FDG PET/MRI

ABSTRACT

Plexiform schwannoma (PS), a subtype of schwannoma, is a rare benign nerve sheath tumor characterized by a multinodular plexiform growth pattern. It is usually confined to the head and neck or skin. Pelvic PS is an extremely rare occurrence and signifies a challenge for the imaging diagnosis. In this work, we present a 42-year-old woman with pelvic PS, who was initially suspected of malignant tumor on 18F-FDG PET/MRI but confirmed as PS by postoperative pathology. We consider that this case would contribute to the literature and provide a further insight into diagnosing this kind of rare tumor.

Machine-Learning Approach to Differentiation of Benign and Malignant Peripheral Nerve Sheath Tumors: A Multicenter Study

BACKGROUND

Clinicoradiologic differentiation between benign and malignant peripheral nerve sheath tumors (PNSTs) has important management implications.

OBJECTIVE

To develop and evaluate machine-learning approaches to differentiate benign from malignant PNSTs.

METHODS

We identified PNSTs treated at 3 institutions and extracted high-dimensional radiomics features from gadolinium-enhanced, T1-weighted magnetic resonance imaging (MRI) sequences. Training and test sets were selected randomly in a 70:30 ratio. A total of 900 image features were automatically extracted using the PyRadiomics package from Quantitative Imaging Feature Pipeline. Clinical data including age, sex, neurogenetic syndrome presence, spontaneous pain, and motor deficit were also incorporated. Features were selected using sparse regression analysis and retained features were further refined by gradient boost modeling to optimize the area under the curve (AUC) for diagnosis. We evaluated the performance of radiomics-based classifiers with and without clinical features and compared performance against human readers.

RESULTS

A total of 95 malignant and 171 benign PNSTs were included. The final classifier model included 21 imaging and clinical features. Sensitivity, specificity, and AUC of 0.676, 0.882, and 0.845, respectively, were achieved on the test set. Using imaging and clinical features, human experts collectively achieved sensitivity, specificity, and AUC of 0.786, 0.431, and 0.624, respectively. The AUC of the classifier was statistically better than expert humans (P = .002). Expert humans were not statistically better than the no-information rate, whereas the classifier was (P = .001).

CONCLUSION

Radiomics-based machine learning using routine MRI sequences and clinical features can aid in evaluation of PNSTs. Further improvement may be achieved by incorporating additional imaging sequences and clinical variables into future models.

Hepatic Schwannoma on 18F-FDG PET/CT

Schwannoma is a slow-growing benign tumor, which originates from Schwann cells and is usually asymptomatic. The most common sites of schwannomas are the head, neck, and extremities. However, a schwannoma located in the liver is extremely rare. Here, we report a 53-year-old woman with a hepatic lesion accidentally found by ultrasound. It was highly suggestive of hepatic cholangiocarcinoma by MRI. F-FDG PET/CT could not exclude hepatic malignant tumor due to its high metabolism. Finally, it was confirmed as hepatic schwannoma by postoperative pathology.

Pancreatic Schwannoma on FDG PET/CT

A 55-year-old woman underwent FDG PET/CT to evaluate a pancreatic mass. The images showed elevated FDG activity in the uncinated process of the pancreas, suggestive of malignancy. However, pathological examination from the resected lesion demonstrated pancreatic schwannoma.