June 01, 1997

An Unusual Type of Metaplasia in the Synovium of an Osteoarthritic Joint

 

Mariano Alvira, M.D.
Department of Pathology
Middletown Regional Hospital
Middletown, Ohio 45042

The synovium consists of fibroconnective tissue lined by Type A and Type B synovial cells. In the normal joint, the Type A cells predominate. The ultrastructural features of the type A cells is that of scant or absent endoplasmic reticulum and prominent golgi complexes that are associated with vesicles. The ultrastructural features of the Type A synovial cells suggest that they are responsible for the production of hyaluronic acid. The Type B synovial cell has prominent rough endoplasmic reticulum and predominates in chronic arthritides. In degenerative arthritides, the usual type of metaplasia is that of chondroid metaplasia. The following case report illustrates the occurrence of an unusual type of synovial metaplasia that occurred in an osteoarthritic joint.

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Light Microscopy

Clinical History

A 61 year old male was seen by his orthopaedic physician because of complaints of knee pain and swelling. He also had a long history of degenerative osteoarthritis.

The patient's past medical history was significant for Duke's Stage A, colloid adenocarcinoma of the sigmoid colon that had been diagnosed two years before his present symptoms of knee pain and joint swelling.

Arthroscopic examination of the knee revealed an absence of normal synovial fluid. The joint cavity was filled with copious amounts of gelatinous material and scattered loose bodies. There was extensive degenerative changes involving the articular surfaces of the joint.

Partial synoviectomy was performed.

The preoperative carcinoembryonic antigen (CEA) level was 0.3 ng /ml. A postoperative CEA level, performed on material from the knee joint was 0.5 ng /ml.

Five years after the synoviectomy, the patient died. The cause of death was atherosclerotic heart disease. There was no clinical evidence of recurrent adenocarcinoma. Permission for autopsy was not granted.

 

 

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