How Advanced Melanoma Is Staged and Worked Up

Introduction

When melanoma may have spread, the next few weeks are usually spent on a workup: a set of tests that answer two questions — exactly how far has the melanoma traveled, and what are its molecular features? The answers set the stage, and the stage points to the treatment.

The workup for advanced melanoma has several parts: a careful staging system that combines the primary tumor, the lymph nodes, and any distant spread; cross-sectional imaging and a brain scan; blood work; testing of the tumor tissue for treatable mutations; a second look at the pathology; and a team discussion that pulls it all together.

This page walks through each step in plain language. For what the resulting labels mean, see what "advanced" melanoma means. For how the primary tumor itself is measured and described, see Breslow depth explained and how to read your melanoma pathology report.

The AJCC 8th Edition TNM System in Plain Terms

Melanoma is staged with the American Joint Committee on Cancer (AJCC) system, now in its 8th edition. It rests on three measurements, abbreviated TNM:

• •T — the primary tumor. Chiefly its Breslow thickness in millimeters, and whether the surface is ulcerated (broken) under the microscope. Thickness is grouped as T1 (≤1 mm) through T4 (>4 mm).
• •N — the regional lymph nodes. How many nodes contain melanoma, whether the spread was microscopic (found on biopsy) or clinically detected, and whether there are in-transit, satellite, or microsatellite deposits in the skin and lymphatic channels near the primary.
• •M — distant spread. Whether melanoma has reached distant skin or nodes (M1a), lung (M1b), other organs (M1c), or the central nervous system (M1d) — and, layered onto each, whether the blood LDH level is normal or elevated.

The three letters combine into a stage from I to IV. You may also hear "clinical stage" (based on exam and imaging before surgery) and "pathologic stage" (revised after the nodes and tumor are examined under the microscope). For a stage-by-stage tour, see what your melanoma stage means.

Sentinel Lymph Node Biopsy and How a Positive Node Changes the Stage

For a primary melanoma that is thick enough to carry a meaningful risk of spread but shows no obvious nodal involvement, surgeons often perform a sentinel lymph node biopsy at the same time as the wide local excision. A tracer identifies the first one or two nodes the melanoma would drain to, and those nodes are removed and examined closely.

• •A negative sentinel node keeps the melanoma at stage I or II and usually means no further nodal surgery.
• •A positive sentinel node moves the melanoma to stage III, even when nothing could be felt or seen on a scan. This is the microscopic (clinically occult) form of nodal spread.
• •The findings guide what comes next — most often ultrasound surveillance of the node basin rather than removing all the remaining nodes, plus a discussion of adjuvant medication.

When a node is large enough to feel or shows up on imaging, a needle biopsy is done instead, and a positive result places the melanoma at clinically detected (macroscopic) stage III.

Blood Work, Including LDH

Blood tests for advanced melanoma are modest in scope. There is no blood test that diagnoses melanoma or replaces imaging, but a few results matter:

• •LDH (lactate dehydrogenase) is part of the stage IV definition itself. An elevated LDH points to a larger amount of melanoma in the body and a less favorable outlook, and it is tracked over time as a rough marker of response.
• •Baseline organ-function tests — blood counts, liver and kidney panels, and thyroid and other hormone levels — are drawn before immunotherapy or targeted therapy so that side effects can be detected against a known starting point.
• •Circulating tumor DNA (ctDNA) blood assays are being studied as a way to monitor melanoma between scans, but they are not yet a standard part of staging.

An LDH level can rise for reasons unrelated to cancer, such as recent vigorous exercise or muscle injury, so it is interpreted alongside the imaging rather than on its own.

Pathology Re-Review and the Multidisciplinary Tumor Board

Two final steps tie the workup together:

• •Pathology re-review. When care moves to a melanoma center, a specialized dermatopathologist re-examines the original slides. Thickness, ulceration, mitotic rate, margins, and the diagnosis itself are all reconfirmed, because these details drive staging and treatment. Re-review occasionally revises the reading in ways that matter. See how to read your melanoma pathology report.
• •Multidisciplinary tumor board. A medical oncologist, surgical oncologist, radiation oncologist, dermatopathologist, and radiologist review the case together. They agree on the stage, decide what — if anything — should be removed surgically, and choose the systemic plan. Guidelines recommend that advanced melanoma be managed this way rather than by one clinician alone.

By the end of the workup you should have a clear stage, a map of where the melanoma is, a BRAF (and, where relevant, NRAS/KIT) result, and a written plan agreed on by the team.

Conclusion

Staging advanced melanoma is a coordinated process, not a single test. The AJCC TNM system organizes what is known about the primary tumor, the lymph nodes, and any distant spread; imaging and a brain MRI show where the melanoma is; LDH and baseline blood work add context and a starting point for monitoring; and molecular testing of the tumor tissue reveals whether targeted therapy is possible.

Pulling those threads together is the job of a multidisciplinary team. The workup can feel like a lot of appointments in a short time, but each piece narrows the options to the treatment most likely to help — and gives everyone a shared baseline to measure progress against.