Final answer:
Atypical lymphocytes are characterized by large nuclei, irregular shapes, and increased cytoplasm, and appear darker with Wright stain. These features, along with techniques like immunohistochemistry, aid in the diagnosis of lymphomas.
Step-by-step explanation:
Atypical lymphocytes, often found in conditions such as viral infections or lymphoma, exhibit distinct morphological features that differ from typical lymphocytes. Atypical lymphocytes are generally larger, with an irregular shape and may have a larger quantity of cytoplasm. Notably, they present a darker appearance under the microscope after being stained with Wright stain because of their large nuclei that actively absorb the stain. In the case of Burkitt lymphoma, for example, the abnormal lymphocytes are characteristically large and purple with vacuoles, visible as white spots, when viewed through a fine-needle aspirate of a tumor. This atypical appearance can be a critical feature for pathologists when performing diagnostics on lymphoid tissues.
Furthermore, immunohistochemistry can be employed to determine the specific type of lymphoma. Through this technique, labeled antibodies are used to identify specific cell-surface antigens, producing a color change where the antigen is present, thus facilitating the diagnosis of lymphoma subtypes based on physical changes and antigen expression.