A 48-year-old woman with a 3 cm invasive lobular carcinoma (ILC) and a 2.5 cm invasive ductal carcinoma (IDC) of the same breast is being counselled on surgical options. Which feature best distinguishes the surgical management approach between these two histological types?

Explanation

## ILC vs IDC: Surgical and Surveillance Implications ### Biological Behaviour Differences **Key Point:** Invasive lobular carcinoma (ILC) has a **higher propensity for bilateral breast involvement and multicentric disease** compared to IDC. This translates to more stringent contralateral breast surveillance and, in some cases, consideration of contralateral prophylactic mastectomy. ### Comparison Table: ILC vs IDC | Feature | ILC | IDC | |---------|-----|-----| | **Histology** | Single-file growth, loss of E-cadherin | Glandular/tubular structures | | **Bilateral breast cancer risk** | 20–25% over lifetime | 5–10% over lifetime | | **Multicentric disease** | Higher (10–20%) | Lower (5–10%) | | **Margin assessment** | Difficult (infiltrative pattern) | Easier (well-demarcated) | | **Breast-conserving therapy** | Feasible if margins adequate | Standard option | | **Axillary staging** | Required (same as IDC) | Required (same as ILC) | | **Contralateral surveillance** | Enhanced MRI screening recommended | Standard mammography | ### High-Yield Clinical Pearl **Clinical Pearl:** ILC is often called the "great imitator" because of its infiltrative growth pattern and higher risk of occult disease. Many surgeons recommend **contralateral breast MRI screening** for ILC patients, and some advocate for contralateral prophylactic mastectomy in high-risk cases (e.g., family history, BRCA mutation). ### Surgical Management Algorithm ```mermaid flowchart TD A[Invasive Lobular Carcinoma]:::outcome --> B{Candidate for BCT?}:::decision B -->|Yes, adequate margins| C[Breast-conserving therapy + Enhanced contralateral surveillance]:::action B -->|No, or extensive disease| D[Mastectomy ± Contralateral prophylactic mastectomy]:::action E[Invasive Ductal Carcinoma]:::outcome --> F{Candidate for BCT?}:::decision F -->|Yes| G[Breast-conserving therapy + Standard surveillance]:::action F -->|No| H[Mastectomy]:::action C --> I[MRI screening of contralateral breast annually]:::action D --> J[Consider genetic counselling & BRCA testing]:::action ``` ### Mnemonic **Mnemonic:** **ILC = Infiltrative, Insidious, Increased bilateral risk** — Remember the three I's to recall the key surgical implications. [cite:Robbins & Cotran 10e Ch 24; Harrison 21e Ch 89]