Lymphosarcoma: Wright's stain, 1000x

Malignant lymphomas, or lymphosarcomas are frequently (but not always!) characterized by the predominance of immature lymphocytes, which eventually replace the normal lymphoid population. A diagnosis of malignant lymphoma can be made based on cytology when immature lymphocytes account for more than 50% of the cell population. However, it is possible for neoplastic cells to account for less than 50% of the cellular population, making it difficult to make a diagnosis based on cytology. Generally, neoplastic immature lymphoid cells may be larger than neutrophils, possess granular chromatin, have visible nucleoli (red arrow), and have a nucleus to cytoplasm ratio that is lower than that of a mature lymphocyte (yellow arrow). Also note the presence of mitotic figures in this microphotograph. It is important to remember that the observation of mitotic figures alone does not indicate a malignant change. In the case of a well differentiated lymphoma (or lymphoma comprising small lymphocytes), histology will generally be necessary for a diagnosis. This can also be said of any cytology of an enlarged lymph node presenting a predominance of mature lymphocytes without an obvious inflammatory component or increased number of plasma cells to suggest lymphadenitis or lymph node hyperplasia, respectively. In such a case, the architecture offered by histopathology will allow for a more definite diagnosis.