**Question:** A 31-year-old woman has had a persistent fever for the past 2 months. Her temperature has ranged from 38.3°C to 38.6°C on multiple occasions. On physical examination, she has diffuse abdominal pain and mild splenomegaly, but no hepatomegaly or lymphadenopathy. Laboratory studies show Hgb, 13.2 g/dL; Hct, 39.8%; MCV, 930 mm³; platelet count, 242,000/mm³; and WBC count, 12,290/mm³ with 71% segmented neutrophils, 19% lymphocytes, and 10% monocytes. CT imaging of her abdomen shows an ill-defined pelvic soft-tissue density mass with a mottled lucent center and a small, square, radiopaque area. Review of her medical record reveals that a salpingo-oophorectomy for ectopic pregnancy was performed on the left side 3 months ago. Which of the following is the most likely cause of her persistent fever?

A. Infection
B. Malignancy
C. Autoimmune disease
D. Injury

**Correct Answer:** B. Malignancy

**Core Concept:**

In this scenario, we are dealing with a patient who has had a history of a left-sided salpingo-oophorectomy for an ectopic pregnancy three months ago. Ectopic pregnancies are a type of pregnancy where the fertilized egg implants itself in a location other than the uterus, most commonly the fallopian tubes, but can also occur in the cervix, ovary, or abdomen. After surgical intervention, there is a risk of infection at the site of surgery due to contamination or inadequate surgical technique.

**Why the Correct Answer is Malignancy:**

The most likely cause of persistent fever in this patient is a post-operative infection at the site of surgery, which is common after salpingo-oophorectomy due to the surgical intervention itself and the possibility of inadequate sterilization of the surgical field. Surgical site infections are usually polymicrobial, involving both aerobic and anaerobic organisms.

**Why Other Options are Incorrect:**

A. Infection: Although infection is a possible cause of fever, the patient has undergone surgery three months ago, and the fever persists. Infection would typically resolve within a few weeks after surgery, not persist for three months.

C. Autoimmune disease: Autoimmune diseases are unlikely to cause fever after a surgical intervention, as they are chronic conditions that would not typically present with fever post-operatively.

D. Trauma: While trauma can cause fever, the patient's history of surgery and fever persistence makes this option less likely. Trauma-induced fever usually resolves within a few days to weeks, not months post-operatively.

In conclusion, a post-operative infection is the most probable cause of the patient's persistent fever. The other options are less likely due to the timing of fever onset and duration following surgery.