We are very grateful to Dr. Chen for his interest in our article 1 concerning cytology in salivary duct carcinoma. The histological criteria we used in the selection of our cases are firmly based on the most recent World Health Organization 2 and Armed Forces Institute of Pathology 3 classifications, which do not yet recognize the subentity termed ''low-grade salivary duct carcinoma.'' For this reason, we did not mention Dr. Chen's observation in our article.
Knowledge of salivary tumors is not yet complete. Parotid and mammary glands are similar histologically and embryologically and develop similar tumors. The problems in the histological classification of mammary ductal in situ and invasive lesions are well known. In salivary pathology, it is reasonable to expect a growing number of publications in the future concerning subtypes of different entities. However, we totally agree with Dr. Chen and with the observations made by Delgado et al. 4 and Khurana et al. 5 that ''low-grade salivary duct carcinoma'' is a serious candidate as a distinctive variant of salivary duct carcinoma and represents the end-spectrum of its differentiation. Its existence is supported, in contrast to our cases, by a clement clinical evolution and long-term survival with no evidence of recurrence or metastasis. One of the goals of preoperative cytological sampling of salivary tumors is the classification into high-or low-grade, benign or tumor-like. ''Low-grade salivary duct carcinoma'' is a new and challenging entity, as evidenced by the high rate of false-negative cytological diagnoses.