Localized nodular synovitis mimicking metastatic melanoma in a patient with metastatic melanoma on whole-body F-18 FDG PET/CT with MRI and pathological correlation

Pigmented villous nodular synovitis mimicking metastases on 18F-FDG PET/CT in a patient with rectal mucosal melanoma: a case report

BACKGROUND

Mucosal melanomas are rare and have a high potential for metastasizing. Surgical resection is the treatment of choice for single distant metastases. Malignant melanoma usually shows the highest uptake of fluorine-18 fluorodeoxyglucose (¹⁸F-FDG). ¹⁸F- FDG positron emission tomography /computed tomography (PET/CT) is usually used for melanoma staging. An extensive literature review revealed only 4 published case reports and an original paper involving 8 cases (12 cases in total) of patients with skin melanomas in whom pigmented villous nodular synovitis (PVNS) mimicked metastatic melanoma, however, none of the melanomas reported were of rectal mucosal origin.

CASE PRESENTATION

A 60-year-old woman presented with recent diagnosis of rectal mucosal melanoma, two additional ¹⁸F-FDG-avid lesions in the left ankle and left foot were detected on ¹⁸F-FDG PET/CT. Metastases were initially suspected; however, the final diagnosis was PVNS.

CONCLUSIONS

This is the first report of PVNS mimicking metastases on ¹⁸F-FDG PET/CT in a patient with rectal mucosal melanoma. Although high ¹⁸F-FDG-avid lesions in patients with rectal mucosal melanoma are highly suspected to be metastasis and warrant an meticulous examination, the present case is a reminder that in such patients, not all lesions with high ¹⁸F-FDG uptake, especially those near a joint, are metastases and that more extensive resection is unnecessary.

Diffuse-Type Tenosynovial Giant Cell Tumor of the Thoracic Spine: Appearance on FDG PET/CT

D-TGCT (diffuse-type tenosynovial giant cell tumor) is a benign proliferative disorder of the synovial membranes that usually occurs in the appendicular skeleton, especially large joints such as the knee, hip, and elbow. It rarely involves the spine. In this report, we describe a rare case of D-TGCT in the thoracic spine, which showed a lytic lesion with high FDG uptake. It can mimic metastases or neurogenic tumors and should be included in the differential diagnosis of spinal tumors.

Successful treatment of a diffuse type tenosynovial giant cell tumor in the thoracic spine mimicking spinal metastasis by frozen recapping laminoplasty in a patient with thyroid cancer

PURPOSE

Tenosynovial giant cell tumor of the diffuse type (TGCT-D) involving the spine is rare. Its differential diagnosis includes metastatic disease; however, there have been few reports of spinal TGCT-D mimicking spinal metastasis in patients with a history of malignancy.

METHODS

We report on a 35-year-old woman with a history of papillary thyroid cancer who was diagnosed with TGCT-D of the thoracic spine mimicking spinal metastasis. Preoperative computed tomography (CT) revealed a 1.0 × 1.0-cm lytic bone lesion involving the left T7 vertebral lamina, pedicle, and the T6-7 facet joint; the thoracic spine lesion was markedly fluorodeoxyglucose-avid on positron-emission tomography/computed tomography (PET/CT).

RESULTS

Spinal metastasis was initially suspected given the patient's history of papillary thyroid cancer. Total excision was performed with recapping laminoplasty. The resected lamina was frozen in liquid nitrogen and used as a frozen autograft (frozen recapping laminoplasty) for spinal reconstruction with posterior instrumentation. Histological findings supported a diagnosis of TGCT-D. The patient had no evidence of local recurrence 2 years post-surgery. Bone union was achieved 3 years post-surgery.

CONCLUSIONS

TGCT-D can mimic metastasis in PET/CT and should be included in the differential diagnosis if a lytic lesion affecting the posterior elements of the vertebrae involves the facet joints. CT-guided biopsy is recommended for accurate diagnosis when an occult tumor, such as TGCT, is incidentally detected on PET-CT, even in patients with a history of malignant neoplasm. Frozen recapping laminoplasty is useful for complete resection of a spinal tumor, preventing local recurrence, and preservation of the posterior spinal elements.

Pigmented villonodular synovitis of the cervical spine: case report and review of the literature

Pigmented villonodular synovitis (PVNS) is an uncommon, benign, but locally aggressive lesion characterized most commonly by synovial proliferation of the appendicular large joints, but occasionally involving a bursa or the tendon sheath. PVNS of the spine is rare, typically involving the posterior elements. The lytic radiographic appearance and fludeoxyglucose avidity of PVNS may mimic malignant bone lesions, including metastatic disease or myeloma. On T₁ and T₂ weighted, and gradient recalled echo MRI sequences, the low signal intensity may mimic giant cell tumour of the bone, gout or synovial amyloid deposits, thus posing a diagnostic dilemma for the imagers and the treating clinicians. We present a pathologically confirmed case of PVNS of the cervical spine in a 49-year-old female, detailing her imaging work-up, describing histopathological correlation and highlighting the lesion location and involvement of the joint space as useful imaging discriminators for diagnosing PVNS of the cervical spine.

Nonsurgical giant cell tumour of the tendon sheath or of the diffuse type: are MRI or 18F-FDG PET/CT able to provide an accurate prediction of long-term outcome?

PURPOSE

To investigate whether MRI (RECIST 1.1, WHO criteria and the volumetric approach) or (18)F-FDG PET/CT (PERCIST 1.0) are able to predict long-term outcome in nonsurgical patients with giant cell tumour of the tendon sheath or of the diffuse type (GCT-TS/DT).

METHODS

Fifteen "nonsurgical" patients with a histological diagnosis of GCT-TS/DT were divided into two groups: symptomatic patients receiving targeted therapy and asymptomatic untreated patients. All 15 patients were evaluated by MRI of whom 10 were treated, and a subgroup of 7 patients were evaluated by PET/CT of whom 4 were treated. Early evolution was assessed according to MRI and PET/CT scans at baseline and during follow-up. Cohen's kappa coefficient was used to evaluate the degree of agreement between PERCIST 1.0, RECIST 1.1, WHO criteria, volumetric approaches and the reference standard (long-term outcome, delay 505 ± 457 days). The response rate in symptomatic patients with GCT-TS/DT receiving targeted therapy was also assessed in a larger population that included additional patients obtained from a review of the literature.

RESULTS

The kappa coefficients for agreement between RECIST/WHO/volumetric criteria and outcome (15 patients) were respectively: 0.35 (p = 0.06), 0.26 (p = 0.17) and 0.26 (p = 0.17). In the PET/CT subgroup (7 patients), PERCIST was in perfect agreement with the late symptomatic evolution (kappa = 1, p < 0.05). In the treated symptomatic group including the additional patients from the literature the response rates to targeted therapies according to late symptomatic assessment, and PERCIST and RECIST criteria were: 65 % (22/34), 77 % (10/13) and 26 % (10/39).

CONCLUSION

(18)F-FDG PET/CT with PERCIST is a promising approach to the prediction of the long-term outcome in GCT-TS/DT and may avoid unnecessary treatments, toxicity and costs. On MRI, WHO and volumetric approaches are not more effective than RECIST using the current thresholds.

Tenosynovial Giant Cell Tumor of Diffuse Type Mimicking Bony Metastasis Detected on F-18 FDG PET/CT

Tenosynovial giant cell tumor of diffuse type (TGCT-D) is a locally aggressive neoplasm that arises in the tendon sheath, bursa, or synovium. It typically involves the appendicular skeleton and rarely involves the axial skeleton. Because there are no specific findings of TGCT-D based on imaging studies or clinical symptoms, TGCT-D can be confused with other primary or metastatic bone tumors. We report findings of TGCT-D involving the T9 vertebra incidentally detected on F-18 FDG PET/CT in a patient with papillary thyroid cancer.

Pigmented villous nodular synovitis mimicking metastatic melanoma on PET-CT

INTRODUCTION

Positron Emission Tomography - Computed Tomography (PET-CT) is routinely utilized in the management of melanoma, either as a part of staging workup or during surveillance. Since melanomas have a high metastatic potential, any FDG avid lesion is considered suspicious for recurrence. We report a case of a FDG avid lesion, diagnosed during melanoma surveillance, its management and review of literature.

PRESENTATION OF CASE

A 58 year-old-male underwent wide local excision for melanoma of the left cheek, and one year post-operatively a PET-CT that revealed a hypermetabolic focus in his right subscapularis muscle, which upon resection was diagnosed as Pigmented Villonodular Synovitis (PVNS).

DISCUSSION

PVNS is a rare benign giant cell tumor that requires no additional treatment in asymptomatic individuals. PET-CT is used for staging and surveillance of numerous malignancies, including melanoma. A hypermetabolic lesion on a PET-CT scan in the setting of malignancy is always suspicious for recurrence.

CONCLUSION

The surgeon is reminded of a uncommon benign FDG avid lesion. Typical location, nonspecific symptoms and characteristic imaging findings help cue in the diagnosis of PVNS and a tissue diagnosis will establish the diagnosis, thus avoiding unnecessarily aggressive surgical management.