A case report of pigmented villonodular synovitis (PVNS) in a patient with small bowel melanoma in a 73-year-old female who underwent a staging FDG PET scan after surgical resection of the primary will be presented.
There was intense focal FDG accumulation in a soft tissue lesion in the left knee infrapatellar soft tissues anteriorly which was reported as a possible metastasis. No other metastases were detected on the whole body FDG PET scan.
Following which the patient had x rays and MRI with gadolinium of the knee. MRI was reported to favour metastasis.
Patient underwent a surgical resection which was proven to be PVNS on histology.
PVNS represents a benign, hypertrophic synovial process characterized by villous, nodular, and villonodular proliferation and pigmentation from hemosiderin (1).
The condition is usually asymptomatic but can present with pain, swelling, and decreased range of movement in the affected joint. Although most common in the knee, PVNS can occur in any joint space (3).
The treatment of choice for PVNS of all types is surgical resection, with complete synovectomy
being particularly important in cases of diffuse intraarticular disease. Recurrence is more
frequent with diffuse intraarticular PVNS, and adjuvant radiation therapy may also be employed
for treatment in these cases. Malignant PVNS is rare and difficult to distinguish, both pathologically
and radiologically, from multiple local recurrences of benign disease unless there is metastatic
involvement of the lungs or lymph nodes (2).
Given the patient's history of cancer and the high SUV, the lesion was initially considered a malignancy. The objective of this case report is to illustrate that even a high-SUV mass detected with PET imaging does not necessarily indicate malignancy, and thus a benign lesion like PVNS can also demonstrate such elevated signal.