Okay, let's tackle this question. The patient is a 22-year-old nursing woman with a tender, erythematous area around the nipple and a yellow fluid draining from a fissure. The question is about the type of inflammatory cells present in the fluid.

First, I need to figure out the condition. The symptoms point to mastitis, which is common in lactating women. Mastitis is usually caused by bacterial infection, often Staphylococcus aureus. The presence of a fissure suggests a possible abscess or infection-related lesion.

Now, the key here is the type of inflammatory cells. In acute bacterial infections, the immune response typically involves neutrophils. Neutrophils are the first responders to bacterial infections and are part of the innate immune system. They are responsible for phagocytizing bacteria and are a hallmark of acute inflammation.

But wait, let me make sure. The options might include other cells like lymphocytes, macrophages, eosinophils, or plasma cells. Let's think: in acute inflammation, neutrophils predominate. Chronic inflammation would have lymphocytes and plasma cells. Eosinophils are more for parasitic infections or allergic reactions. Macrophages are involved in chronic inflammation or in resolving the infection by phagocytizing debris.

Since the patient has a recent infection (acute mastitis), the fluid would show neutrophils. The yellow color of the fluid (pus) is characteristic of neutrophil accumulation. The presence of an open fissure and purulent discharge supports an acute bacterial process.

So the correct answer should be neutrophils. The other options are incorrect because they relate to different types of inflammation or conditions. For example, lymphocytes would be more in a chronic infection or autoimmune process. Eosinophils are not typical here. Macrophages are part of the later stages or in granulomatous inflammation. Plasma cells are part of a chronic response.

Clinical pearl: Remember that acute bacterial infections present with neutrophils, while chronic or viral infections have lymphocytes. This is a key point for exams.

**Core Concept**
This question tests knowledge of inflammatory cell types in acute bacterial infections, specifically *mastitis* in lactating women. **Neutrophils** are the hallmark of acute bacterial inflammation due to their role in phagocytosing bacteria and releasing enzymes at sites of infection.

**Why the Correct Answer is Right**
The patient’s symptoms (erythema, tenderness, purulent drainage) indicate **acute mastitis**, often caused by *Staphylococcus aureus*. Neutrophils dominate the inflammatory response in acute bacterial infections. Under microscopy, the exudate (yellow fluid) would show **numerous neutrophils** due to their rapid recruitment to the site of infection via chemotaxis. The presence of a fissure suggests a localized abscess, further supporting neutrophilic infiltration.

**Why Each Wrong Option is Incorrect**
**Option A:** Lymphocytes are characteristic of **chronic inflammation** (e.g., granulomatous disease) or viral infections, not acute bacterial infections.
**Option B:** Eosinophils are associated with **parasitic infections** or allergic reactions, not bacterial mastitis.
**Option C:** Plasma cells are markers of **chronic inflammation** and antibody production, not acute

✓ Correct Answer: D. Neutrophils