A 29-year-old female presents with severe pain during menstruation (dysmenorrhea). During workup, an endometrial biopsy is obtained. The pathology repo from this specimen makes the diagnosis of chronic endometritis. Based on this pathology repo, which one of the following was present in the biopsy sample of the endometrium?

**Core Concept**
Chronic endometritis is a condition characterized by chronic inflammation of the endometrium, often resulting from an underlying infection, immune response, or foreign body presence. The condition can lead to symptoms such as dysmenorrhea, irregular bleeding, and infertility.

**Why the Correct Answer is Right**
Chronic endometritis typically involves the presence of lymphocytes, plasma cells, and histiocytes in the endometrium, indicating a chronic inflammatory response. The condition can also be associated with the presence of microorganisms such as bacteria, viruses, or fungi, which may cause the inflammation. In this case, the patient's symptoms and the pathology report suggest that the endometrial biopsy sample would show evidence of a chronic inflammatory response.

**Why Each Wrong Option is Incorrect**
* **Option A:** Although endometrial hyperplasia can cause irregular bleeding and dysmenorrhea, it is not typically associated with chronic inflammation or the presence of lymphocytes and plasma cells.
* **Option B:** Endometrial polyps are benign growths that can cause irregular bleeding, but they are not associated with chronic inflammation or immune cells.
* **Option C:** Adenocarcinoma of the endometrium is a malignant tumor that can cause irregular bleeding, but it would be characterized by atypical glandular cells and would not typically involve a chronic inflammatory response.

**Clinical Pearl / High-Yield Fact**
Chronic endometritis can be a cause of infertility and recurrent pregnancy loss, and it is essential to investigate and treat the underlying cause of the inflammation to improve reproductive outcomes.

**Correct Answer:** C. **Lymphocytes, plasma cells, and histiocytes.**

✓ Correct Answer: D. Plasma cells