FDG PET/CT and MRI Features of Pathologically Proven Schwannomas

Case report: Thoracic schwannoma as a diagnostic pitfall in both 18F-Choline PET/CT and 18F-FDG PET/CT

We report increased 18F-FDG uptake in the right posterior mediastinal region in a 70-year-old woman following the discovery of a mass in the aftermath of a bronchitis episode. We also report increased 18F-Choline uptake in the right posterior mediastinal region in a 66-year-old man with newly discovered prostate cancer, which may indicate the presence of mediastinal metastases. Both patients had a thoracic MRI showing an intense gadolinium enhancement in the same region, consistent with thoracic schwannomas, which were subsequently proven histologically. This case highlights that schwannoma is a diagnostic pitfall in both 18F-FDG and 18F-Choline PET/CT.

18 F-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 18 F-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.

Positron Emission Tomography/Computed Tomography Transformation of Oncology: Musculoskeletal Cancers

The past 25 years have seen significant growth in the role of positron emission tomography/computed tomography (PET/CT) in musculoskeletal oncology. Substantiative advances in technical capability and image quality have been paralleled by increasingly widespread clinical adoption and implementation. It is now recognized that PET/CT is useful in diagnosis, staging, prognostication, response assessment, and surveillance of bone and soft tissue sarcomas, often providing critical information in addition to conventional imaging assessment. As individualized, precision medicine continues to evolve for patients with sarcoma, PET/CT is uniquely positioned to offer additional insight into the biology and management of these tumors.

Surgical Management of Lumbosacral Plexus Tumors

BACKGROUND

Lumbosacral plexus tumors are uncommon, and because of their deep location and proximity to critical nerves subserving lower extremity function, understanding surgical approaches and short-term outcomes is important.

METHODS

In a retrospective case series of lumbosacral plexus tumor surgeries performed from May 2000 to July 2021 by a single neurosurgeon, demographic information, clinical presentation, imaging studies, and operative outcomes were analyzed.

RESULTS

A total of 42 patients with mean age of 48.3 years (range, 16-84 years) underwent surgery for a lumbosacral plexus tumor. Patients presented with leg pain (n = 25; 59.5%), followed by back/flank pain (n = 5; 11.9%), abdominal/pelvic pain (n = 5; 11.9%), leg weakness (n = 5; 11.9%), and leg numbness (n = 3; 7.1%). The most common tumor pathology was schwannoma (n = 20; 50.0%) followed by neurofibroma (n = 9; 22.5%). A retroperitoneal approach was used in all cases. Gross total resection was achieved in 23 (54.8%) patients, and only 1 (2.4%) patient exhibited symptomatic tumor recurrence after subtotal resection of a malignant tumor. Mean follow-up was 33.1 months (range, 1-96 months). Postoperatively, patient neurological status remained unchanged or improved (n = 37; 88.1%). Complications were infrequent, with 4 (9.5%) patients experiencing new sensory symptoms and 1 patient (2.4%) experiencing new anticipated motor weakness after en bloc resection of a malignant tumor.

CONCLUSIONS

Indications for surgery include pain and/or neurological symptoms attributable to the lesion or large size if asymptomatic. Careful study of preoperative imaging is necessary to determine the best approach. Intraoperative nerve stimulation is essential to preserve function and guide extent of resection in benign tumors.

Multimodality imaging features of USP6-associated neoplasms

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

Incidental Finding of a Tongue Schwannoma Mimicking Local Recurrence of Squamous Cell Carcinoma on a Systematic Follow-up 18F-FDG PET/CT

ABSTRACT

Schwannomas are usually benign, rare, and slow-growing nerve sheath tumor composed of Schwann cells. They develop in the head and neck area in approximately 25% to 40% of cases, of which 1% in the oral cavity, where the tongue remains the preferred site. Malignant transformation occurs in approximately 8% to 10% cases. We report a unique case of a histologically proven FDG-avid schwannoma of the left mobile portion of the tongue, showing an 18F-FDG avidity on PET/CT, which was a false-positive result for local recurrence in a patient followed for squamous cell carcinoma.

Presacral Benign Schwannoma Mimics Malignancy on 18F-FDG and 68Ga-FAPI PET/CT

ABSTRACT

We present findings of FDG PET/CT and FAPI PET/CT in a 55-year-old woman with a history of black stools and low-back pain. Pelvic CT detected a giant presacral mass that was suspected to be malignant. 18F-FDG and 68Ga-FAPI PET/CT showed that the mass had intense activity. Pathological examination confirmed the mass as a benign schwannoma.

Diagnostic and Imaging Approaches to Chest Wall Lesions

Chest wall lesions are relatively uncommon and may be challenging once they are encountered on images. Radiologists may detect these lesions incidentally at examinations performed for other indications, or they may be asked specifically to evaluate a suspicious lesion. While many chest wall lesions have characteristic imaging findings that can result in an accurate diagnosis with use of imaging alone, other entities are difficult to distinguish at imaging because there is significant overlap among them. The interpreting radiologist should be familiar with the imaging features of both "do not touch" benign entities (which can be confidently diagnosed with imaging only, with no need for biopsy or resection unless the patient is symptomatic) and lesions that cannot be confidently characterized and thus require further workup. CT and MRI are the main imaging modalities used to assess the chest wall, with each having different benefits and drawbacks. Chest wall lesions can be classified according to their predominant composition: fat, calcification and ossification, soft tissue, or fluid. The identification or predominance of signal intensities or attenuation for these findings, along with the patient age, clinical history, and lesion location, can help establish the appropriate differential diagnosis. In addition, imaging findings in other organs, such as the lungs or upper abdomen, can at times provide clues to the underlying diagnosis. The authors review different chest wall lesions classified on the basis of their composition and highlight the imaging findings that can assist the radiologist in narrowing the differential diagnosis and guiding management. ^©RSNA, 2022.

Intracavernous Schwannoma Characterized With 18F-FDG, 68Ga-DOTATOC, and 18F-Choline PET

ABSTRACT

We report the case of a 75-year-old man with history of prostate cancer whose left intracavernous lesion was successfully characterized by 3 PETs performed successively with different tracers. This poorly characterized tumor was initially discovered on an MRI conducted to investigate an acute diplopia and slowly growing during follow-up. On 18F-FDG PET, the lesion showed no significant uptake, and no extracranial lesion was found nor did it have increased 68Ga-DOTATOC uptake. Finally, this tumor displayed a high 18F-choline uptake, and no extracranial lesion was revealed with this tracer. The diagnosis of schwannoma without malignancy criterion was proven by biopsy.