Pigmented villonodular synovitis

Pigmented villonodular synovitis (PVNS)

The diffuse type of tenosynovial giant cell tumor, better known as pigmented villonodular synovitis, is a proliferative disorder of the synovial tissue.

Clinically, the process manifests as involvement of a single large joint (chronic monoarthropathy). Due to the structural peculiarities of the altered tissue, periodic hemorrhages occur into the joint cavity—recurrent hemarthrosis. Externally, the pathology may mimic soft tissue swelling spreading along the tendon sheath.

The primary imaging modality is MRI. The scans reveal joint effusion and signs of synovitis. A key feature is the accumulation of hemosiderin (a blood breakdown product) within the synovium. Hemosiderin causes a characteristic decrease in signal intensity (low SI) across all types of pulse sequences. Treatment consists of extensive synovectomy, although patients frequently experience recurrences.

Vascular anomalies: tumors and malformations

According to the ISSVA classification, vascular pathologies are divided into two fundamentally different groups: true tumors and malformations.

Vascular tumors (e.g., infantile hemangioma) are benign neoplasms that appear in the first weeks of life in 2–3% of infants. They are typically characterized by an initial rapid growth phase followed by slow involution.

Vascular malformations are congenital dysplastic vascular channels. They may be imperceptible at birth, grow proportionally with the patient, and never regress spontaneously. Malformations are classified by flow rate:

• High-flow: arteriovenous malformations (AVMs) and fistulas. They manifest with pain, bleeding, and tissue overgrowth. Large AVMs can cause heart failure. The overlying skin pulsates, a thrill (thrill) is palpable, and a bruit is auscultated.
• Low-flow: venous, capillary, lymphatic, and combined.

Venous malformations (VMs)

Up to 2/3 of all low-flow malformations are venous malformations. Historically, they have been mistakenly referred to as "hemangiomas" in adults.

They consist of abnormal, thin-walled veins with a deficiency of smooth muscle and a fat-containing hamartomatous stroma. These vessels dilate with age.

Clinical picture:

• A congenital lesion, often with an area of cyanotic skin.
• The tumor is soft, easily compressible, and exerts no mass effect.
• Dimensions vary depending on body position (due to blood filling).
• There is no local temperature elevation or pulsation.

They are most commonly located in the head and neck (40%) or extremities (40%). Due to slow blood flow, thrombi frequently form within them and subsequently calcify, resulting in phleboliths (phleboliths). Consumption of clotting factors inside the lesion leads to localized coagulopathy, which carries a risk of bleeding during trauma. They are treated via percutaneous sclerotherapy.

Diagnostic imaging of vascular malformations

The diagnostic workup is based on three modalities:

1. Radiography: demonstrates a lobulated mass, occasionally with remodeling of the adjacent bone. A specific marker is the presence of multiple phleboliths (rounded calcifications with a lucent center).
2. Ultrasound: visualizes hypoechoic tubular structures and phleboliths. Color Doppler ultrasound shows monophasic low-speed flow or no detectable flow. The crucial differential sign distinguishing it from sarcoma is compressibility with the transducer.
3. MRI:
4. On T1-weighted images — heterogeneous moderately hyperintense signal, with possible bright foci (fat or methemoglobin from thrombi).
5. On T2-weighted images — hyperintense serpiginous channels.
6. Fluid-fluid levels and areas of signal void (signal void) from phleboliths or fibrosis are visible.
7. Contrast administration shows delayed diffuse enhancement (unlike lymphatic malformations, where contrast accumulates in the septa).

MRI checklist: assess flow type, extent, involvement of adjacent tissues (skin, muscles, bone marrow), and communication with feeding/draining vessels.

Soft tissue chondromas

Extraskeletal chondromas are benign neoplasms composed of hyaline cartilage. They are located outside the bone and synovium, with no connection to the periosteum.

They are most commonly found in patients aged 30–60 years. The preferred location is the fingers of the hand (about 80% of cases). They are typically solitary, lobulated lesions measuring less than 3 cm. They may intimately abut the joint capsule or tendon, and when exerting pressure on the bone, can cause erosion and remodeling. Radiographs demonstrate characteristic cartilaginous mineralization (punctate or curvilinear) and occasionally ossification.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Specifics of performing MRI protocols for evaluating hemosiderin
• ISSVA classification of vascular anomalies: complete structure
• The role of sclerotherapy in the management of low-flow malformations
• Differential diagnosis of soft tissue chondromas and chondrosarcomas

Other topics in the "Musculoskeletal System" section

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