Cytological features of oral malignant lymphoma in scraping liquid-based cytology: Cases of plasmablastic lymphoma and anaplastic lymphoma kinase-positive anaplastic large cell lymphoma.

The main purpose of cytological examination in the oral region is to screen for squamous cell carcinoma or intraepithelial neoplasms; thus, the background tends to be considered a deterrent for microscopy. From this perspective, liquid-based cytology (LBC) is favorable for preparing clear samples with few backgrounds. However, background hemocytes are sometimes of critical importance in the diagnosis. We report two cases of oral malignant lymphoma, plasmablastic lymphoma, and anaplastic large cell lymphoma in which careful observation of the background in scraping LBC sample contributed to the early diagnosis. Atypical lymphoid cells were observed only in a very small part of the LBC samples from the presented patients; however, cytological findings, such as large lymphoid cells with outstanding nucleoli, large mitotic cells, or intermediate-to-large lymphoid cells with pleomorphic nuclei were sufficient for obtaining a cytological diagnosis of malignant lymphoma. Although the number and cell size of leukocytes in LBC with Papanicolaou staining were significantly different from those in air-dried conventional smears with Romanovsky staining, which are commonly preferred for the discrimination of hemocytes, the corresponding cytological features could be observed. Therefore, attention should be paid to the background as well as squamous epithelium to prepare for such unexpected cases. The LBC examination with Papanicolaou staining alone can suggest the possibility of malignant lymphoma.