Discussion

Diagnosis

Tumoral calcium pyrophosphate dihydrate (CPPD) crystal deposition disease. 

Discussion

Tumoral calcium pyrophosphate dihydrate crystal deposition disease is one of the rarest forms of CPPD crystal deposition disease, with fewer than 50 total cases described in the literature as recently as 2001. While calcium pyrophosphate deposits are typically seen in the meniscus, articular cartilage, intervertebral disc and ligamentum flavum, the most common location of tumoral CPPD crystal deposition disease is the temporomandibular joint, and involvement into the adjacent bone is common. Most patients with tumoral CPPD crystal deposition disease lack evidence of CPPD crystal deposition in any other joints. Classically tumoral CPPD crystal deposition disease occurs in elderly patients (median age 60 years) with a female predominance. Patients usually do not have familial CPPD deposition disease or other associated metabolic disorders. Serum calcium and phosphate levels are also typically normal. Recurrence is not unusual, and has been noted after both complete and incomplete surgical excision. 

Histologically, the lesions are described as basophilic calcific deposits with metaplastic cartilage, either with or without atypia, and typically with foreign body granulomatous reaction and associated fibrous stroma. The etiology of the relationship between chondrometaplasia and CPPD crystal deposition is unknown; however there has been speculation that the presence of metaplastic cartilage is an essential factor responsible for CPPD crystal deposition in synovium.

The differential diagnosis for tumoral CPPD deposition disease includes chondroid neoplasm with dystrophic calcifications, including chondrosarcoma, as well as tophaceous gout. Importantly, the presence of chondroid areas with cellular atypia may be suggestive of a malignant cartilage tumor. Thus it is important to recognize tumoral CPPD deposition disease to avoid misdiagnosis.

References

Beutler A, Rothfuss S, Clayburne G, Sieck M, Schumacher HR, Jr. Calcium pyrophosphate dihydrate crystal deposition in synovium. Relationship to collagen fibers and chondrometaplasia. Arthritis Rheum. 1993;36(5):704-715.

Ishida T, Dorfman HD, Bullough PG. Tophaceous pseudogout (tumoral calcium pyrophosphate dihydrate crystal deposition disease). Hum Pathol. 1995;26(6):587-593.

Yamakawa K, Iwasaki H, Ohjimi Y, et al. Tumoral calcium pyrophosphate dihydrate crystal deposition disease. A clinicopathologic analysis of five cases. Pathol Res Pract. 2001;197(7):499-506.
 

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