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Lymphoscintigraphy and the sentinel lymph node
The sentinel node is the first node to receive lymphatic drainage from the tumour; a technetium-labelled agent injected near the tumour travels to it, lymphoscintigraphy shows where, and the surgeon finds it with a hand-held probe — and if it is clean, dissection of the whole basin can be avoided.
Why it matters in the exam
The exam asks about indications, injection technique and situations in which it must not be done. In breast cancer: a T1–T2 tumour with a clinically clear axilla; contraindications: palpable or needle-positive nodes (proceed to nodal treatment) and inflammatory breast cancer. Injection is periareolar or subareolar, or peritumoral. In melanoma: a Breslow depth of 0.8 mm or more, or less with ulceration (T1b and above), with clinically clear axillae and groins; injection is intradermal at 4 points around the tumour or scar.
In melanoma of the trunk, and especially near the midline of the back, drainage may reach several basins — both axillae, the groins or the neck — so preoperative lymphoscintigraphy is essential; there may also be "in-transit" nodes between the tumour and the basin. In the head and neck and the pelvis SPECT/CT localises deep nodes. Agents: Tc-99m-labelled colloid, or Tc-99m tilmanocept, which binds the mannose receptor (CD206) on macrophages and dendritic cells in the node. Combining with blue dye or ICG improves the detection rate.
In theatre the hottest node is removed, plus any node with a count of at least 10% of it. Further indications: early cervical and vulvar cancer, early oral cavity cancer, penile cancer, and sometimes endometrial cancer. In pregnancy the low-activity radioactive agent is accepted, whereas blue dye is avoided because of the risk of anaphylaxis. Lymphoscintigraphy is also used to diagnose lymphoedema: delayed transit, "dermal backflow" and fewer nodes.
Key points
- Sentinel node — first in the drainage; clean — no dissection.
- Breast T1–T2 with a clear axilla; not in inflammatory cancer.
- Melanoma from 0.8 mm or with ulceration.
- Trunk — drainage to several basins; lymphoscintigraphy is essential.
- Remove every node with at least 10% of the hottest.
Summary table
| Tumour | Indication | Injection | Contraindication or note |
|---|---|---|---|
| Breast | T1–T2, clinically clear axilla | Periareolar or peritumoral | Positive nodes, inflammatory cancer |
| Melanoma | Breslow 0.8 mm or more or ulceration | Intradermal at 4 points | Trunk — several drainage basins |
| Early cervix or vulva | Small tumour, clear nodes | Cervical or peritumoral | SPECT/CT for the pelvis |
| Early oral cavity | T1–T2, clear neck | Peritumoral | SPECT/CT for the neck |
A free exam question
לפניך מיפוי בלוטת זקיף של אישה עם אבחנה חדשה של קרצינומה של צוואר הרחם . מהו הטיפול המתאים ביותר לאור הממצאים במיפוי? (the question as examined, in Hebrew)
- א. כריתה של3 קשרי לימפה באגן ימין וקשר לימפה אחד באגן משמאל
- ב. כריתה של קשר לימפה אחד באגן מימין וקשר לימפה אחד באגן משמאל
- ג. טיפול סיסטמי בגלל ריבוי הממצאים באגן
- ד. טיפול סיסטמי בגלל הקליטה בכבד
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Sources
- EANM/SNMMI Practice Guideline for Lymphoscintigraphy and Sentinel Lymph Node Biopsy in Melanoma, 2015 — Injection technique and drainage basins
- EANM Practice Guidelines for Lymphoscintigraphy and Sentinel Lymph Node Biopsy in Breast Cancer, 2013 — Indications, injection sites and contraindications
- NCCN Guidelines: Cutaneous Melanoma, 2025 — Sentinel lymph node biopsy criteria
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.