These authors contributed equally to this work.
Pigmented villonodular synovitis (PVNS) is a proliferative, recurrent and locally invasive disease of the synovium. The symptoms of the disorder are not typical and thus it is very often misdiagnosed. Most of the times, magnetic resonance imaging presents the nodular model of development and sets the basis for the diagnosis. The final diagnosis will be set by the pathological evaluation of the lesion’s biopsy. PVNS may be localized (nodule with a clear boundary with/without presence of single pedicle) or diffuse (extensive involvement of the adjacent nerves and vessels). Depending on the extension of the PVNS, a different management approach is performed, lesion excision vs. resection, followed by radiotherapy respectively. We report a case of diffuse PVNS in the knee joint, treated with surgical excision and adjuvant radiotherapy as well as follow-up imaging after a time period of 3 years.
Pigmented villonodular synovitis (PVNS) is a rare, benign, proliferative but potentially locally aggressive, recurrent clinical entity. Usually, it is associated with t(1;2)(CSF-1;COL6A3) chromosomal translocation which results in overexpression of CSF1 (colony stimulating factor 1) [
Hantes et al. [
A 37-year-old male patient presented with a 6-month history of swelling in the region of the knee joint, accompanied by progressively deteriorating pain and reduced joint functionality. He had a free personal (no trauma) and family medical history. Plain radiographs of the knee joint demonstrated no significant abnormalities and thus it was diagnosed and treated as chondromalacia patellae.
As treatment for chondromalacia patellae showed no improvement of the symptoms, further investigation and new imaging of the joint region was conducted. New plain radiographs presented no significant abnormalities and so magnetic resonance imaging (MRI) was performed (
The definite diagnosis of PVNS was set by the histopathological and immunohistochemical examination of tissue samples taken from the anterior site of the patellofemoral joint as more superficial site of the lesion. The histopathological examination of the biopsy showed synovial membrane characterized by papillary and solid structure, synoviocyte hyperplasia, many hemosiderin granules and intense inflammatory infiltration of lymphocytes, plasmatocytes, a lot of histiocytes/macrophages and a few multinucleated giant cells. The immunohistochemical evaluation was positive for the anti-CD68 antibodies, the histiocytes, the anti-CD45/LCA (leukocyte common antigen) and the lymphocytes, and negative for the anti-S-100, anti-CD34, anti-vimentin, anti-SMA (smooth muscle antibody), anti-Desmin, anti-AEI/AE3 and anti-HMB-45 antibodies. No histological features associated with malignancy had been identified (
The treatment plan included the surgical excision of the PVNS lesion with open synovectomy and then adjuvant radiotherapy. For the total excision of this diffuse PVNS lesion, more than one operation was required. Through the first surgical procedure, the biggest part of the lesion located at the posterior side of the tibiofemoral joint was removed through a posterior knee approach. Taking into account the affection by the lesion to nearby structures such as nerves and blood vessels, a critical intra-operative point, the remnant residual disease was considered to be the minimum possible. A second operation was performed 2 months later, so as to remove the residual mass of the anterior side of the tibiofemoral joint by an anterior incision and medial parapatellar approach. The patient then underwent adjuvant postoperative external radiotherapy four weeks after the second surgical operation in order to reduce the recurrence and improve the local control rates [
Almost 2 months after the last surgery and a few days after the last radiotherapy fraction, the maximum range of the knee joint moves achieved was -5º of extension to 80º of flexion. Eighteen months after the end of the treatment, the MRI presented no significant alterations. Maximum range achieved was 0º of extension to 90º of flexion. Three years after the end of the treatment, the MRI again demonstrated no pathological alterations (
Diffuse PVNS is a clinical entity that needs careful management in its diagnosis and treatment. The pathological identification of no malignant features is very important. Two or more surgical procedures may be needed for the total or near total excision of the lesion. In cases it affects important nearby structures (nerves and blood vessels) the near total excision is the unavoidable way. The goals of PVNS treatment are the following: (1) preventing disease recurrence, (2) relieving pain and stiffness, and (3) preserving joint function [
All authors declare that written informed consent was obtained from the patient for publication of this case report and accompanying image.
No potential conflict of interest relevant to this article was reported.
None.
The data that support the findings of this study are available from the corresponding author upon reasonable request.
(A) Plain anterior-posterior radiograph of the knee. No significant abnormalities. (B) Sagittal view of the left knee with three-dimensional fast spoiled gradient-echo (FSPGR) sequence. Extensive diffuse pigmented villonodular synovitis occupying the posterior and anterior part of the knee joint with extra-articular extension demonstrated with low to medium signal and blooming artifact due to hemosiderin (white arrows).
Diffuse pigmented villonodular synovitis. (A) Histological examination of tissue samples taken from the lesion (H&E staining, original magnification ×20). Synoviocyte hyperplasia, a lot of hemosiderin granules and intense inflammatory infiltration of lymphocytes, plasmatocytes, many histiocytes/macrophages and a few multinucleated giant cells. (B) Immunohistochemical staining of tissue samples taken from the lesion with the anti-CD68 antibody (original magnification ×20). CD68-positive mononuclear cells and multinucleated giant cells detected—CD68 stain in the cytoplasm of those cells.
(A, B, C) Target volume of the treated area. (D) Dose volume histogram and radiation treatment planning system information.
Magnetic resonance imaging after 3 years. No local recurrence of pigmented villonodular synovitis is noticed.