A 32-year-old multiparous woman is on day 10 postpartum and exclusively breastfeeding her second child. She presents with a 2-day history of pain in the upper outer quadrant of the left breast, localized erythema, and a palpable firm nodule. Her temperature is 38.8°C. Milk from the affected breast appears normal. She has been feeding regularly from both breasts. What is the most likely diagnosis and next best management?

Explanation

## Diagnosis: Lactational Mastitis **Key Point:** This clinical presentation — localized breast pain, erythema, fever (38.8°C), and a **firm (not fluctuant) nodule** on day 10 postpartum in an actively breastfeeding woman — is classic for **lactational mastitis**, NOT a breast abscess. The absence of fluctuance, the normal milk appearance, and the short 2-day symptom history all point away from abscess formation. ### Differential Diagnosis: Mastitis vs. Abscess | Feature | Lactational Mastitis | Breast Abscess | |---|---|---| | **Onset** | Acute (24–72 hrs) | Subacute (5–10 days) or after failed mastitis treatment | | **Palpable mass** | Firm, indurated area (no fluctuance) | **Fluctuant, tender mass** | | **Systemic symptoms** | Fever, malaise, myalgia | High fever, systemic toxicity | | **Milk appearance** | Normal | May be purulent if duct involved | | **Management** | **Antibiotics + continued breastfeeding** | Ultrasound + drainage + antibiotics | | **Prognosis** | Resolves in 48–72 hrs with treatment | Requires procedural intervention | **High-Yield:** The key discriminator between mastitis and abscess is **fluctuance** on examination or a confirmed fluid collection on ultrasound. A "firm nodule" without fluctuance in the context of 2 days of symptoms is consistent with indurated mastitis, not an abscess. Abscess typically develops after 5–10 days of untreated or inadequately treated mastitis. ### Why Option D (Breast Abscess) Is Incorrect The stem describes a **firm** nodule — not a fluctuant mass. Breast abscess requires either clinical fluctuance or ultrasound-confirmed fluid collection for diagnosis. Proceeding directly to needle aspiration or drainage without these features is inappropriate and potentially harmful. The 2-day symptom duration also argues against abscess, which typically takes longer to develop. ### Correct Management for Lactational Mastitis 1. **Antibiotics** — First-line: dicloxacillin or flucloxacillin (anti-staphylococcal); if MRSA suspected, use trimethoprim-sulfamethoxazole or clindamycin. Duration: 10–14 days. 2. **Continue breastfeeding** — Cessation increases milk stasis, worsens engorgement, and raises abscess risk. WHO and AAP both recommend continued breastfeeding during mastitis treatment. 3. **Supportive measures** — Warm compresses before feeding, adequate breast emptying, analgesics (ibuprofen preferred for anti-inflammatory effect). 4. **Reassess in 48–72 hours** — If no improvement, obtain ultrasound to rule out abscess formation. **Clinical Pearl:** According to Williams Obstetrics (26e, Ch. 37), lactational mastitis affects approximately 10% of breastfeeding women and is most common in the first 6 weeks postpartum. *Staphylococcus aureus* is the most common causative organism. Continued breastfeeding is strongly recommended as it does not harm the infant and prevents progression to abscess. **Warning:** Do NOT stop breastfeeding in mastitis — this is a common but dangerous misconception. Milk stasis promotes bacterial proliferation and increases the risk of abscess formation. [cite: Williams Obstetrics 26e Ch 37; WHO/UNICEF Breastfeeding Counselling Guidelines]