A very rare benign tumour in the parotid region: calcium pyrophosphate dihydrate crystal deposition disease

Calcium pyrophosphate dihydrate crystal deposition disease, exhibits severa l clinical manifestations, from absence of symptoms to severely destructive arthropathy or conditions simulating neoplasm, which is frequently related to the temporomandibular joint. Fifteen of the 31 reported cases of tophac eous pseudogout were found in the head and neck region. A patient presented with a parotid swelling, which initially was suspected to be malignant bec ause of the following findings: radiodensity, progression into the joint, o sseous destruction of the major ala of the sphenoid and a fine needle aspir ate with crystals, osteoblasts, megakaryocytes and irregular cells of varyi ng size. At surgery there was found a tumour consisting of a white, firm gr itty material. It progressed to the skull base where material had to be lef t, because of the presence of the nerves and vessels. A frozen specimen was reported to be benign. Histological examination showed inflammatory cells, macrophages, a chondroid material with embedded metaplastic chondroid cell s and giant cells of foreign body type. Crystal examination of X-ray diffra ction revealed calcium pyrophosphate dihydrate.