Abstract
Background : Chondroblastoma is a benign bone tumor which usually occurs in the epiphysis of long bones in young persons. Chondroblastoma involving the temporal bone is rare. Few case reports on its cytological findings have been published.
Case 1 : A 50-year-old man presented with a 1.5 cm mass in the left temporal bone. Pre-operative fine needle aspiration cytology made no definite diagnosis. The lesion was partially removed, and histologically diagnosed as a chondroblastoma. Stamp preparation was obtained at additional excision of the remaining tumor. Both aspiration and touch smear cytology showed a mixture of mononuclear round tumor cells and osteoclast-type giant cells (OCGCs) within a clear background. Mononuclear cells had round to oval nuclei with grooved or constricted nuclear membrane. Their cytoplasm was well circumscribed and stained light green.
Case 2 : A 58-year-old man presented with a 2 cm mass in the right temporal bone. The touch smear preparation which was obtained at tumorectomy contained the same mononuclear cells and OCGCs as case 1. Additionally, extracellular matrix with metachromasia was observed.
Conclusion : Chondroblastoma of the temporal bone should be distinguished from other diseases that are composed of mononuclear cells and OCGCs. Along with clinical and radiological findings, cytological features such as characteristic chondroblasts and extracellular matrix with metachromasia are helpful for differential diagnosis.
