Encountering “abnormal lymphocytes” on a lab report can cause concern. Lymphocytes are a type of white blood cell, part of the body’s immune system that protects against infections and diseases. They circulate through the blood and lymphatic system, identifying and neutralizing threats. Understanding this term can clarify the finding and subsequent medical discussions.
What Are Abnormal Lymphocytes?
Normal lymphocytes are small, round cells with a large nucleus and a small amount of cytoplasm. B cells produce antibodies, and T cells fight infected or abnormal cells. An “abnormal” lymphocyte differs in appearance from typical lymphocytes under a microscope. Changes can involve the cell’s size, shape, or the characteristics of its nucleus and cytoplasm.
Abnormal lymphocytes fall into two categories: reactive (or atypical) and malignant. Reactive lymphocytes are non-cancerous cells activated in response to infection, inflammation, or other immune challenges. They often appear larger than normal, with more abundant, sometimes darker blue cytoplasm, and an irregular or indented nucleus. Malignant lymphocytes are cancerous cells, often characterized by a more uniform appearance, even with atypical features. They are clones of a single cell that have malfunctioned in their growth or death processes.
Causes of Abnormal Lymphocytes
The presence of abnormal lymphocytes often indicates the body is mounting an immune response, with most cases stemming from benign, reactive causes. Viral infections are frequent culprits, including Epstein-Barr virus (EBV), which causes infectious mononucleosis, and cytomegalovirus (CMV). Other viral infections like hepatitis, HIV, influenza, and some bacterial infections such as whooping cough or cat-scratch disease can lead to reactive lymphocytes. Autoimmune disorders, including lupus and rheumatoid arthritis, and certain drug reactions can also trigger an increase in reactive lymphocytes.
Less commonly, abnormal lymphocytes can be a sign of blood cancer. These include various types of leukemia and lymphoma, where the abnormal cells are malignant. Chronic lymphocytic leukemia (CLL) is a cancer involving B lymphocytes that accumulate in the blood and bone marrow. Acute lymphoblastic leukemia (ALL) and different forms of lymphoma, such as non-Hodgkin lymphoma and Hodgkin lymphoma, can also present with abnormal lymphocytes. In these conditions, the lymphocytes are monoclonal, meaning they originate from a single malfunctioning cell.
The Diagnostic Process
When abnormal lymphocytes are identified, doctors follow a structured process to determine the underlying cause. Initial detection often occurs through a complete blood count (CBC) with differential, a common blood test measuring different cell types, including lymphocytes. If the CBC shows an elevated lymphocyte count, particularly above 4,000 lymphocytes per microliter in adults, further investigation is warranted.
The next step involves a peripheral blood smear, where a laboratory professional examines a blood drop under a microscope. This allows for visual assessment of lymphocyte morphology, helping distinguish between reactive and potentially malignant cells based on their size, nuclear characteristics, and cytoplasmic features. If malignancy is suspected, more specialized tests may be ordered. Flow cytometry analyzes specific markers on lymphocyte surfaces, identifying the exact type and determining if cells are clonal, a characteristic of cancerous cells. A bone marrow biopsy may also be performed, especially if bone marrow involvement is a concern, providing a direct sample of blood-forming tissue for detailed examination.
Next Steps After an Abnormal Result
An abnormal lymphocyte count prompts further investigation, rather than being a definitive diagnosis. Subsequent actions depend on the cause identified during the diagnostic process. For reactive lymphocytosis due to a viral infection, such as mononucleosis, the approach often involves “watchful waiting,” as the immune system clears the infection over time, and the lymphocyte count returns to normal without specific intervention. Supportive care, including rest and symptom management, may be recommended for viral illnesses.
If abnormal lymphocytes are linked to a bacterial infection, antibiotics may be prescribed. For autoimmune conditions, treatment focuses on managing the immune system’s overactivity, often with medications like corticosteroids or disease-modifying antirheumatic drugs. When a blood cancer like leukemia or lymphoma is diagnosed, treatment is tailored to the specific type and stage of cancer, which can include targeted therapies, chemotherapy, or immunotherapy. Regular follow-up testing is recommended to monitor lymphocyte levels and ensure they normalize or to track the progression of any underlying condition.