American Association of Critical-Care Nurses (AACN) Certification Practice Test

What are mature lymphocytes indicative of in pleural effusions?

1. Acute infection

2. Malignancy

3. Chylothorax

4. Transudative effusion

The correct answer is: Chylothorax

Mature lymphocytes in pleural effusions are typically indicative of a specific type of condition related to the immune response. When mature lymphocytes are present in significant numbers, this strongly suggests the likelihood of a lymphocytic process, which is often associated with malignancies or chronic inflammatory conditions, such as tuberculosis. Mature lymphocytes are not typically seen in chylothorax, which is characterized by a milky appearance of the pleural fluid due to the presence of chyle, containing fat globules, and often lymphocytes but predominantly immature or activated ones, due to trauma or obstruction of lymphatic drainage. Transudative effusions usually feature a predominance of plasma and are caused by systemic factors, such as congestive heart failure or nephrotic syndrome, and don’t typically present with high lymphocyte counts. Thus, the presence of mature lymphocytes is more indicative of conditions like malignancy rather than chylothorax or transudative processes. Their cell morphology and count help healthcare professionals narrow down differential diagnoses for the underlying cause of the pleural effusion.