How is melanoma diagnosed

Sentinel Lymph Node Biopsy (SLNB)

Lymph nodes, part of the body’s lymphatic system, are small bean-shaped organs that help fight infection. There are large groups of lymph nodes on both sides of the neck, in the armpits, and in the groin. If there is high enough risk that the melanoma has grown into the inner layers of the skin and into the lymphatic system, your doctor may order a sentinel lymph node biopsy. The presence or absence of melanoma cells in the lymph nodes is an important prognostic factor and it indicates whether there is high risk of recurrence. It is also used to decide the type of treatment you may need.

The SLNB is a surgical procedure during which a small amount of radioactive substance is injected into the area where the melanoma was removed. The lymph nodes that absorb the injected fluid first are the sentinel lymph nodes. There are usually between one and five sentinel nodes.

If the cancer has spread, the sentinel nodes are the most likely node to have cancer within them. The surgeon will remove these nodes and check them for cancer cells. The removal of the sentinel lymph nodes is usually done under a general anaesthetic at the same time as a wide local excision of the lesion/mole.

Fine Needle Aspiration Biopsy 

During the physical exam, your doctor will have felt the lymph nodes nearest the melanoma to see if they are enlarged, irregular, or firm, because such nodes may indicate the cancer has spread to the lymph nodes. If they are enlarged, irregular, or firm, your doctor may recommend a fine needle aspiration biopsy. A fine needle aspiration biopsy is performed with local anaesthetic. A slender needle is placed through the skin and into the suspicious lymph node. A small tissue sample is removed when the needle is withdrawn. An ultrasound or CT scan is often used to guide the needle to the correct node. The sample is then examined by a pathologist under a microscope to see if it contains cancer.

X-Ray

An x-ray may be used to look for spread.

Ultrasound

An ultrasound uses sound waves to create a picture of the internal organs, including collections of lymph nodes, called lymph node basins, and soft tissue. The picture can reveal potential spread.

Computed Tomography (CT or CAT) Scan

A CT scan creates a 3-dimensional picture of the inside of the body using x-rays taken from different angles. A computer combines these images into a detailed, cross-sectional view that shows any abnormalities or tumours. If melanoma has spread, a CT scan can be used to measure the tumour’s size. Sometimes, a special dye called a contrast medium is given before the scan to provide better detail on the image. This dye can be injected into a patient’s vein and/or given as a liquid to swallow.

Magnetic Resonance Imaging (MRI)

An MRI uses magnetic fields, not x-rays, to produce detailed images of the body. MRI can be used to measure the tumour’s size. A special dye called a contrast medium is given before the scan to create a clearer picture. This dye is injected into a patient’s vein.

Positron Emission Tomography (PET) or PET-CT Scan

A PET scan is usually combined with a CT scan (see above), called a PET-CT scan. However, you may hear your doctor refer to this procedure as a PET scan. A PET scan is a way to create pictures of organs and tissues inside the body. A small amount of a radioactive sugar substance is injected into the patient’s body. This sugar substance is taken up by cells that use the most energy. Because cancer tends to use energy actively, it absorbs more of the radioactive sugar substance than normal. Cancer cells, or affected tissues in the body will show up as bright spots on PET scans, which help to identify areas in which melanoma may have spread.

Typical Terms & Language on a Pathology Report

Type of melanoma

The type of melanoma will be identified: Cutaneous (Acral, Nodular, Superficial Spreading, Lentigo Maligna, Amelanotic, Desmoplastic), Ocular or Mucosal.

Stage

Staging is a scoring system that assigns a number (I-IV) and often with a substage (a-d) that describe the tumour, node, and metastasis (TMN) scores and other prognostic factors.

Breslow depth

Breslow depth is a measurement in millimetres of the thickness of the primary tumour from the top layer of the skin to its deepest point. The thicker a melanoma, the more likely it has spread to the lymph nodes or other parts of the body. Melanomas are classified as:

• in situ – found only in the outer layer of the skin
• thin – less than 1 mm (0.04 inch)
• intermediate – 1–4 mm (0.04 – 0.1575 inch)
• thick – greater than 4 mm (0.1575 inch)

Margins

Margins are the area of normal tissue surrounding the melanoma. If there are melanoma cells in or very close to that area, more surgery may be required.

Mitotic rate

The mitotic rate is the measure of how fast melanoma cells are dividing and multiplying. When pathologists study a melanoma, they will count the number of actively dividing cells that they see. Averaging this number gives the mitotic count, and it is reported as the number of mitoses per square millimetre (mm²). (For example, ≤1 mitoses/mm².) A high mitotic count means more tumour cells are dividing at a given time and is associated with a worse prognosis.

Ulceration

Ulceration is the absence of the top skin layer of the melanoma. If ulceration is present, the stage classification of a melanoma is increased. Ulceration is thought to reflect rapid tumour growth, leading to the death of cells in the centre of the melanoma and thus is associated with a worse prognosis. The pathologist can determine whether ulceration is present or absent when s/he reviews the biopsy under the microscope. Patients who report bleeding from their melanoma often have ulceration in the biopsy.

Satellites

Satellite lesions are small nodules of tumour/melanoma located more than 0.05mm from the primary lesion, but less than 2cm. Satellites are described as being present or absent. Some satellite lesions (macroscopic) can be seen with the naked eye. Others, which are smaller (microscopic) can be found only by pathologists. Both macroscopic and microscopic lesions are reported in the pathology report.

Blood vessel / lymphatic invasions

Blood vessel invasion also called angioinvasion, or lymphatic vessel invasion is described as being present or absent. If present, it means that the melanoma has invaded the blood or lymph system and is associated with more aggressively growing melanomas.

vertical growth phase (VGP)

The melanoma is described as either having VGP present or absent. If present, VGP is an indication that the melanoma is growing vertically, or deeper, into the tissues.

Tumour-Infiltrating Lymphocytes (TILs)

The melanoma is described as either having VGP present or absent. If present, VGP is an indication that theTILs describe the patient’s immune response to melanoma. When the pathologist examines the melanoma under the microscope, s/he looks to see whether there are lymphocytes within the melanoma. The amount of lymphocyte invasion/response to the melanoma is described as brisk (a lot of lymphocytes), nonbrisk (some), sparse (few) or absent (none), although occasionally it can be described as mild or moderate. TILs appear to indicate that your immune system has recognized the melanoma cells as abnormal and is trying to move into the melanoma to attack it. Some studies suggest that the presence of an increasing number of TILs may be associated with a better prognosis.

Melanoma Staging

Cancer staging is a way to describe the extent of cancer in your body, and is explained in more detail under Stages of Melanoma

When to contact your doctor

If you are concerned about an area on your skin, make an appointment.

Don’t hesitate to ask for a second opinion if you think it’s warranted.