M12.2

Clinical Information

• A locally aggressive, diffusely infiltrating tumor, arising in the tendon sheath. It is composed of synovial-like mononuclear cells, hemosiderin-laden macrophages, foam cells, and inflammatory cells. Multinucleated osteoclast-like giant cells are usually present, although in a minority of cases they may be absent or rare. It predominantly affects young adults. Symptoms include joint swelling, pain, and joint effusion.

• Outgrowths of synovial membrane composed of villi and fibrous nodules characterized histologically by hemosiderin- and lipid-containing macrophages and multinucleated giant cells. It usually occurs in the knee.

Details

• M12.2 should not be used for reimbursement purposes as there are multiple codes below it that contain a greater level of detail.

• The 2023 edition of ICD-10-CM M12.2 became effective on October 1, 2022.

• This is the American ICD-10-CM version of M12.2 – other international versions of ICD-10 M12.2 may differ.