Synovial osteochondromatosis

The patient was a 31-year-old woman with an 8-year history of left-sided neck, back, and arm pain associated with weakness and numbness of the left hand following an injury sustained while moving a heavy object. She had been involved in an automobile accident about 1 year prior to presentation. She denied any other constitutional symptoms such as weight loss, fever, chills, nausea, vomiting, diarrhea, or loss of appetite. Physical examination and past medical history were otherwise unremarkable.

X-rays of the left shoulder (Figure 1) demonstrated soft tissue calcifications surrounding the left acromioclavicular joint, interpreted as probable old inflammatory or traumatic disease. The glenohumeral joint was normal.

At surgery, a 3 × 2-cm, bosselated, cartilaginous mass and multiple smaller fragments of tissue were removed from the acromioclavicular joint space. The synovium appeared irregular and studded. The patient had an uneventful postoperative course.

The excised specimen consisted of multiple, gray-white nodules of irregular cartilaginous tissue ranging in diameter from 0.3 to 3.5 cm (Figure 2). The cut surface of these nodules was smooth and firm. Microscopic examination revealed nodules of hyaline cartilage with chondrocytes arranged in a clustering pattern (Figure 3). Focal calcification was noted. Chondrocytic atypia was noted focally with occasional binucleated chondrocytes (Figure 4). No necrosis, mitotic figures, spindle cells, myxoid degeneration, or significant cellular crowding was observed.

What is your diagnosis?

Pathologic Diagnosis: Synovial Chondromatosis

Synovial chondromatosis is an uncommon lesion of uncertain etiology. It is characterized by multiple cartilaginous and osteocartilaginous bodies. The knee is the joint most often affected, followed by the hip, elbow, wrist, and ankle. Shoulder involvement is distinctly uncommon, as noted by Small and Jaffe,1 who found only 25 cases of synovia! chondromatosis of the shoulder in a 1981 review of the world literature.

Synovial chondromatosis may progress to cartilaginous metaplasia within the synovial membrane, leading to cartilaginous, osteocartilaginous, or loose bodies within the affected joint space.

Subsynovial fibroblasts may be the cells that undergo metaplasia.2 In response to an undetermined stimulus, these cells undergo metaplastic transformation to chondrocytes, which proliferate and give rise to multiple foci of hyaline cartilage. Once metaplasia occurs, additional accumulation of cartilage results from proliferation of the chondrocytes. 3 These cartilaginous nodules may become pedunculated, protruding into the joint space. They may remain attached to the synovium by a stalk or become detached. If they break from the stalk (autoamputate), intrasynovial loose bodies, or "rice bodies" result. These may undergo secondary ossification or, in some cases, spontaneously regress.4

Milgram5 summarizes 3 phases of this process. In phase 1, chondroid metaplasia of the synovium occurs. No loose bodies are present, and the disease is intrasynovial. In phase 2, chondroid bodies are found both in the synovium and extruded into the joint space. The loose bodies may remain free in the joint space and grow via layering of cartilage and bone. Alternately, the loose bodies may reattach to the synovium and become resorbed.h In phase 3, multiple free bodies are seen within the joint space and the synovium may be quiescent.

Patients typically have symptoms for months to years before seeking treatment.1 Symptoms include mechanical catching or locking, swelling, pain, decreased range of motion, and loss of function.4 A history of trauma to the affected joint is often given. However, the frequency of joint trauma and the infrequency of synovial chondromatosis make it questionable whether trauma is etiologically significant.7

X-ray findings are often characteristic. Calcification may be seen radiographically, depending on the degree of calcification of the lesion. Multiple radiopaque densities are present in the affected joint in a juxta-articular distribution. The densities typically vary from a few millimeters to several centimeters.8

A pathognomic criterion for diagnosis of synovial chondromatosis defined by Jaffe is the presence of cartilaginous foci within the synovial tissue.3 The cartilaginous nodules may be partially calcified or truly ossified, containing fatty bone marrow.9 Chondrocytes occur in groups having a clustering architecture. Cellular atypia and binucleated chondrocytes may be seen,7 but malignant transformation to chondrosarcoma is extremely rare. Synovial chondrosarcoma is the most important entity in the differential diagnosis. Features that favor synovial chondrosarcoma include necrosis, mitotic figures, myxoid stromal change, spindle cells, cellular crowding, and a sheetlike arrangement of cells.10 Local invasion or extension beyond the joint capsule is worrisome for malignancy.5

Our patient's long history (8 years) of pain, benign histologie features, and lack of an invasive growth pattern suggest biologically benign behavior.

References

1. Small R, Jaffe L. Tenosynovial chondromatosis of the shoulder. Bull Hosp It Dis Orthop Inst. 1981;41:37-47.

2. Sarma DP, Huffman EO, Subramanium CV. Synovial chondromatosis. J La State Med Soc. 1990;142:27-30.

3. Jaffe HL. Tumors and Tumorous Conditions of the Bones and Joints. Philadelphia, Pa: Lea & Febiger; 1958:558-567.

4. McFarland EG, Neira CA. Synovial chondromatosis of the shoulder associated with osteoarthritis: conservative treatment in two cases and review of the literature. Am J Orthop. 2000:29:785-787.

5. Milgram JW. Synovial osteochondromatosis: a histopathological study of thirty cases. J Bone joint Surg Am. 1977;59A:792-801.

6. Milgram JW. The development of loose bodies in human joints. Clin Orthop. 1977;124:292-303.

7. Murphy FP, Dahlin DC, Sullivan R. Articular synovial chondromatosis. I Rone hint Surg. 1962;44-A:77-86.

8. Pope TL, Keats TE, deLange EE, Fechner RE, Harvey JW. ldiopathic synovial chondromatosis in unusual sites: inferior radioulnar joint and ischial bursa. Skeletal Radio!. 1987;16:205-208.

9. Fechner RE, Mills SE. Tumors of the Bones and loints. Washington, DC: Armed Forces Institute of Pathology; 1993:279-282. Atlas of Tumor Pathology, 3rd series, fascicle 8.

10. Bertoni F, Unni KK, Beabout JW, Sim FH. Chondrosarcoma of the synovium. Cancer. 1991;67:155-162.

Giovanni D. Lorusso, MD; Deba P. Sarma, MD; Syeda F. Sarwar, MD

Accepted for publication June 30, 2004.

From the Department of Pathology, Louisiana State University Health Sciences Center and Veterans Affairs Medical Center, New Orleans.

The authors have no relevant financial interest in the products or companies described in this article.

Corresponding author: Giovanni D. Lorusso, MD, Department of Pathology, COS-3, Veterans Affairs Medical Center, 1601 Perdido St, New Orleans, LA 70112 (e-mail: glorus@lsuhsc.edu).

Reprints not available from the authors.

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