A case report of chondroblastoma of temporal bone

A rare case of chondroblastoma of the temporal bone with invasion is reported. A 58-year-old man was admitted to our hospital because of a mass in the left preauricular region. A CT scan revealed an osteolytic lesion in the temporal bone invading the adjacent soft tissue and a malignant tumor was suspected clinically. Fine needle aspiration cytology showed a mixture of neoplastic mononuclear cells and multinucleated giant cells. The mononuclear cells had a round to oval nucleus with longitudinal grooves or convolutions. A few cells contained intranuclear cytoplasmic inclusions. A chondroid matrix was revealed by Alcian blue staining. Based on these findings, a chondroblastoma was suspected. Histologically, the tumor was composed of oval or polygonal mononuclear cells with well-defined cytoplasmic borders and scattered multinucleated giant cells. Chondroid foci were present. Several mononuclear cells were found to be positive for anti-S 100 protein antibody by immunohistochemical examination. The cytologic features in aspiration cytology are characteristic and important for diagnosing chondroblastoma.