Nuclear Criteria for Diagnosing Malignancy based on Cytology

In cytology, nuclear criteria serve as a guide in order to establish a diagnosis of malignancy. These criteria include anisokaryosis , a nucleocytoplasmic ratio which is variable or high, macrokaryosis, (nuclei greater than 10 microns in diameter), multiple nuclei in a single cell (especially presenting variability in size within the same cell), an elevated mitotic index, the presence of abnormal mitotic figures (asymmetric, inappropriately aligned), the presence of prominent nucleoli, the presence of irregular or angular nucleoli, the presence of variable nucleolar size within a nucleus, nuclear molding (deformation of nuclei next to each other within a cell), a coarse or blotchy chromatin pattern. Nuclear fragmentation or budding can also be observed and correspond to an irregular nuclear shape. Variability in cell size can also be observed in malignant tumors, however they are not exclusive to these. General characteristics of neoplastic cells include anisocytosis (variability in cell size), macrocytosis (the presence of large cells), hypercellularity (the presence of a highly cellular sample), and polymorphism, the presence of cells of variable shape in a sample.

                 When more than four nuclear criteria are present in a cytologic specimen, a malignant change is likely. However, certain well differentiated malignant tumours can present a relative uniform appearance, making cytologic diagnosis difficult. Also, certain benign lesions can possess enough nuclear variability to suggest a malignant process. A common example of this is fibroplasia in chronic inflammatory lesions. It is important to note which nuclear criteria are present: certain criteria will be stronger indicators of a malignant process, such as asymmetrical mitotic figures, or the presence of nuclei of variable size within the same cell, irregular, fragmented or "budding" nuclei (not to be confused with apoptotic nuclei) as well as prominent and irregular nucleoli within the same nucleus.  

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