BACKGROUND Pleomorphic adenoma (PA) is the most common neoplasm of the major salivary glands. There are three subtypes of malignant PA: carcinoma ex pleomorphic adenoma (CXPA); carcinosarcoma (true malignant mixed tumor) and metastasizing pleomorphic adenoma. The most common subtype of malignant PA is CXPA which develops in primary or recurrent PA. For proper diagnosis of CXPA, a statement of coexistence of pleomorphic adenoma and carcinoma (or carcinoma after prior PA surgery) is needed. Own material is presented because of rarity and clinicopathologic specificity of this neoplasm. METHODS Retrospective analysis of the medical data of 19 patients who were treated at our department because of CXPA from 1990 to 2002 was done. The following clinical factors were evaluated: age, sex, symptoms (time of lasting, evolution), tumor size, invasion of the adjacent structures and facial nerve, neck nodes, clinical stage, treatment outcome. One pathologist reviewed histological material of 18 out of 19 patients who had been operated and pathological factors such as sensitivity and accuracy of fine needle aspiration biopsy, grade, histology and proportion of malignant component in tumor, lymph nodes metastases were analyzed. RESULTS There were 11 men and 8 women, the mean age was 57 years. In 15 cases, tumor was localized in the parotid and in 4 in the submandibular gland. Two patients had history of prior surgery of PA. Duration of symptoms of benign PA was from 2 to 40 years (mean 17.8 years). Symptoms of malignant transformation occurred in 15 patients, the most common were rapid enlargement of tumor, pain and facial nerve palsy. Tumor size varied from 2 to 20 cm with a mean of 6 cm. In 14 patients, the neck was evaluated clinically as No, in 5, examination identified enlarged lymph nodes. Adjacent structures were invaded by neoplasm in 5 cases. Sensitivity and accuracy of fine needle aspiration biopsy in detection of malignant character of PA were 60% and 46% respectively. 17 out of 18 tumors reviewed by the pathologist were high grade. Only in 6 patients, proportion of carcinoma in the mass was less than 50%. The most common malignant component in CXPA was adenocarcinoma (9 cases) and undifferentiated carcinoma (6 cases). Pathologic examination showed metastases to the lymph nodes in 7 out of 10 patients with prior neck dissection. 16 patients were treated surgically (12 of them had also radiation therapy) and 3 patients underwent only (chemo)radiotherapy. Determinate survival at 5 years was 73.6% and in the group treated surgically (alone or with postoperative irradiation) 87.5%. CONCLUSIONS Malignant transformation of PA occurs in 5 to 25% untreated patients, usually after 15-20 years and warning symptoms are present in the most cases. Fine needle aspiration biopsy has insufficient sensibility and accuracy in detection of malignant character of PA. Clinical picture and histopathological examination determinate the diagnosis of CXPA. Proper histological classification of malignant component can be found difficult. Surgical treatment (alone or with postoperative irradiation), if possible, allows to achieve good locoregional control of CXPA. 5-years survival varied between 30 to 76%. The best method of prevention and treatment of CXPA is early and radical removal of all major salivary glands tumors.