Inflammatory lesions can occur due to infectious or non-infectious causes. Compared to tissue cells, inflammatory cells are readily collected by aspirates and scrapings.

Mycobacteria do not stain with routine cytologic stains and can be difficult to visualize.

Normally, only a small amount (milliliters) of fluid are present in the thorax and abdomen.

Round cell tumors are commonly detected as cutaneous or subcutaneous masses. However, the majority of these tumors also appear in other locations.

Fine needle aspiration (FNA) cytology is an excellent adjunctive tool for evaluating internal organs.

Cytology is useful for establishing a diagnosis or can narrow the list of differentials for effusions, masses, lymphadenopathy, or organomegaly.

Small lymphocytes are smaller in size than a neutrophil and have a round nuclei that takes up the majority of the cell.

As the primary cell type present in lymphoid organs is lymphocytes, the first part of this handout will describe the morphologic features of lymphocytes and then briefly describe other methods to assess lymphocytes.

Round cell tumors are commonly detected as cutaneous or subcutaneous masses.