What provides a definitive diagnosis of inflammatory breast cancer (IBC)?

Definitive Diagnosis of Inflammatory Breast Cancer

The definitive diagnosis of inflammatory breast cancer is provided by finding tumor emboli in dermal lymphatics, which is considered the histological hallmark and pathognomonic feature of IBC when present. 1

Diagnostic Criteria for Inflammatory Breast Cancer

• The diagnosis of IBC requires both clinical and pathological components, with the clinical presentation being the primary basis supplemented by essential pathological confirmation 1
• Clinical criteria include rapid onset of breast erythema, edema and/or peau d'orange, and/or warm breast, with or without an underlying palpable mass 1
• The clinical symptoms should have a duration of no more than 6 months, and erythema should occupy at least one-third of the breast 1
• Pathological confirmation of invasive carcinoma from a core biopsy is required as part of the diagnostic process 1

Pathological Features and Dermal Lymphatic Invasion

• Dermal lymphovascular tumor emboli are the histological hallmark of IBC and when present in skin punch biopsy, dermal lymphatic invasion (DLI) is pathognomonic for IBC 1, 2
• DLI presents as dilated dermal lymphovascular spaces filled with tumor emboli that are often retracted away from the surrounding endothelial lining 1
• Despite being pathognomonic, DLI is identified in less than 75% of patients with IBC, making it not an absolute requirement for diagnosis 1, 3
• The presence of DLI significantly impacts prognosis, with studies showing that in patients with diffuse IBC, the presence of DLI increased the risk of relapse 3-fold 3

Role of Imaging and Biopsy in Diagnosis

• Mammography and other radiological investigations are recommended as part of staging work-up, not for primary diagnosis 1
• Current evidence is insufficient to define any radiological signs specific for IBC 1
• Core biopsy to confirm invasive carcinoma, and at least two skin punch biopsies are strongly recommended for patients who meet the clinical diagnostic criteria 1
• The best area to sample is the most prominent area of skin discoloration 1

Common Pitfalls in Diagnosis

• Relying solely on imaging findings (such as mammographic appearance) without clinical correlation may lead to missed diagnoses 1
• Failure to perform skin punch biopsies may miss the opportunity to identify pathognomonic dermal lymphatic invasion 1
• Mistaking inflammatory cell infiltration alone as diagnostic of IBC is incorrect - while inflammation may be present, it is the tumor emboli in dermal lymphatics that are pathognomonic 1, 2
• Laboratory findings such as elevated white cell count, fever, and axillary lymphadenopathy may be present but are not diagnostic criteria for IBC 1, 4
• Ultrasound appearance of cavitation is not a diagnostic feature of IBC 1

Diagnostic Algorithm

1. Evaluate clinical presentation (erythema, edema, peau d'orange, warm breast) 1
2. Confirm duration of symptoms is less than 6 months 1
3. Perform core biopsy to confirm invasive carcinoma 1
4. Obtain at least two skin punch biopsies from the most prominent area of skin discoloration 1
5. Examine skin biopsies specifically for dermal lymphatic invasion 1
6. If dermal lymphatic invasion is present, this confirms the diagnosis 1, 2
7. If dermal lymphatic invasion is absent but clinical criteria are met and invasive carcinoma is confirmed, the diagnosis of IBC can still be made 1, 5