A 68-year-old man with prostate cancer and bone metastases presents with shaking chills and fever. The peripheral WBC count is 1,000/mL (normal =4,000 to 11,000/mL). Which of the following terms best describes this hematologic finding?

**Core Concept**
Leukopenia refers to a decreased peripheral white blood cell (WBC) count, which can be caused by various factors such as bone marrow suppression, infection, or malignancy. In this context, the patient's prostate cancer and bone metastases may be contributing to the development of leukopenia.

**Why the Correct Answer is Right**
The correct answer is **Leukopenia** because the patient's WBC count is significantly below the normal range. This can be attributed to the bone marrow's suppression of WBC production due to the underlying malignancy and metastases. The bone marrow's ability to produce WBCs is impaired, leading to a decrease in the peripheral WBC count.

**Why Each Wrong Option is Incorrect**
**Option A:** **Leukocytosis** is incorrect because it refers to an elevated WBC count, which is the opposite of the patient's condition.
**Option B:** **Leukemoid reaction** is incorrect because it is a reactive process characterized by an elevated WBC count in response to infection or inflammation, which is not applicable in this case.
**Option C:** **Aplastic anemia** is incorrect because it is a more severe condition characterized by a decrease in all blood cell lines (RBCs, WBCs, and platelets), whereas the patient's WBC count is only mildly decreased.

**Clinical Pearl / High-Yield Fact**
A key point to remember is that leukopenia can be a sign of bone marrow failure or suppression, which can be caused by various factors including malignancy, chemotherapy, or radiation therapy.

**Correct Answer:** . **Leukopenia**

✓ Correct Answer: B. Leukopenia