Teaching Case

A 63-year-old diabetic and obese female presented with left breast pain, initially treated for mastitis (clinically diagnosed). She returned with worsening pain, erythema, and swelling. An ultrasound revealed an abscess, and she was discharged and scheduled for drainage (at a specialised centre). Despite adjusted antibiotics, her condition continued to deteriorate.

On the second visit, an ultrasound of the left breast revealed an ill-defined, hypoechoic area with internal echoes consistent with a 3.5 cm abscess, surrounded by oedema and skin thickening (Figure 1).

By the third visit (prior to the scheduled drainage appointment), a repeated ultrasound (not shown) revealed a significant amount of gas, which limited the view of deeper tissues. Consequently, a computed tomography (CT) scan of the thorax was performed, revealing notable stranding of left-sided breast tissue, skin thickening and extensive gas formation within the breast tissue and adjacent pectoral muscles, consistent with gangrene (Figures 2a and 2b). The infection had extended into the anterior chest wall, with significant soft tissue swelling and air tracking along the fascial planes (Figure 3). Reactive axillary adenopathy was also noted (Figure 4).

Background

Mastitis, a common breast infection, typically responds well to antibiotics. However, in postmenopausal women or those with risk factors like diabetes and obesity, mastitis can progress to severe complications, such as abscess formation or necrotising fasciitis [1]. This case highlights the critical need for close monitoring and timely intervention in such high-risk patients.

Clinical Perspective

Necrotising fasciitis is a rapidly advancing, life-threatening infection that affects the soft tissues, including the fascia [1,2]. The diagnosis is made essentially by clinical and surgical findings [1–3]. While commonly seen in extremities, it can involve the breast, particularly in immunocompromised individuals [1]: In this case, the initial diagnosis of mastitis was insufficient, and the patient’s condition worsened, indicating a more severe infectious process.

Imaging Perspective

Ultrasound plays a crucial role as the first-line imaging modality for breast infections, providing valuable insights into the extent of the infection and enabling procedures like percutaneous drainage [1,4–6]. It is essential to capture images from the skin to the chest wall to avoid missing deeper infections [6]. However, in certain cases, such as necrotising fasciitis, ultrasound may be limited in fully assessing the infection [2,6]. While ultrasound can detect air as echogenic foci with posterior dirty shadowing, CT is more sensitive in detecting subcutaneous emphysema and gas formation, making it the preferred modality for evaluating the full extent of such infections [2,6]

Outcome

Following the CT confirmation of necrotising fasciitis, the patient underwent immediate surgical debridement, including a subtotal left-sided mastectomy. Despite aggressive treatment, including broad-spectrum antibiotics and intensive care, necrotising fasciitis has a poor prognosis, requiring ongoing follow-up to monitor for complications [1–3].

Teaching Points

• Mastitis can rarely progress to severe conditions like necrotising fasciitis, especially in high-risk individuals.
• Ultrasound and sometimes CT are crucial for diagnosing complicated infections and guiding treatment.
• Rapid clinical deterioration should prompt immediate advanced imaging and surgical intervention.
• Effective management involves collaboration among emergency physicians, radiologists, surgeons, and infectious disease specialists.

Written informed patient consent for publication has been obtained.