Question 1

Q: What is the definition of a sentinel lymph node?

The primary lymph node draining the tumor.. ### Explanation **Concept Overview** The **Sentinel Lymph Node (SLN)** is defined as the first lymph node (or group of nodes) in a regional lymphatic basin that receives direct lymphatic drainage from a primary tumor. The underlying physiological principle is that lymphatic metastasis occurs in an orderly, step-wise fashion. If the sentinel node is negative for malignancy, there is a high probability (usually >95%) that the remaining nodes in that basin are also free of disease. **Analysis of Options** * **Option A (Correct):** This aligns with the physiological definition. It is the "gatekeeper" node. If the tumor spreads via lymphatics, this node is the first site of metastasis. * **Option B (Incorrect):** A Modified Radical Mastectomy (MRM) involves a formal axillary lymph node dissection (Levels I and II). The nodes removed are based on anatomical boundaries, not necessarily the specific drainage pattern of the tumor. * **Option C (Incorrect):** Proximity does not always equal drainage. Due to the complexity of lymphatic channels, the sentinel node may sometimes be anatomically distant from the tumor while still being the first node to receive its drainage. **Clinical Pearls for NEET-PG** * **Identification:** SLN is identified using **Isosulfan blue/Methylene blue dye** (visualized) and/or **Technetium-99m labeled sulfur colloid** (detected via a gamma probe). * **Most Common Indications:** Breast cancer (T1/T2 lesions) and Malignant Melanoma. * **Skip Metastasis:** This refers to a phenomenon where the SLN is negative, but higher-level nodes are positive. While rare, it is a limitation of SLN biopsy. * **Contraindications in Breast Cancer:** Inflammatory breast cancer, multicentric tumors (relative), and clinically palpable axillary nodes (N1/N2).

Question

What is the definition of a sentinel lymph node?

Accepted Answer

The primary lymph node draining the tumor.

Answer

The first lymph node excised during a modified radical mastectomy.

Answer

The lymph node located nearest to the tumor.

Answer

None of the above.

Surgical Oncology Principles — MCQs

Surgical Oncology Principles — MCQs

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