Posted by Dr James Burt
on 7 May 2017
At the conclusion of the last article I explained the whilst the Breslow thickness and the Clarke Level are the most important factors reported by the pathologist when they examine a melanoma under the microscope.
Even though the factors we will discuss below are not as critical as thickness and level the pathologists do report on several other lessor factors which we know effect outcome of melanoma.
I have listed them below with a brief explanation.
- Architectural type;
Superficial Spreading Melanoma: most common of the melanomas. Appear to be spreading outwards.
Nodular Melanoma: The melanoma appears to be growing vertically downwards( and often form a raised lump or nodule in the skin).
Acral Lentiginous: most common type in dark skinned and Asian populations. More frequently occur on soles of feet, palms of hands or under nails.
Lentigo Maligna Melanoma: tends to occur on sun-exposed areas in older people often very superficial, level 1 or insitu disease.
Rare subtypes: mucosal melanoma, desmoplastic melanoma, nevoid melanoma
- Predominant cell type
- Insitu component - part of the melanoma seen is in the epidermis only
- Invasive component - part of the melanoma invades into the dermis ( the lower layer of the skin)
- Mitoses per square millimeter - A mitosis is seen an actively dividing cell. Counting the mitoses is an attempt to give an indication how actively this melanoma maybe growing
- Tumor infiltrating lymphocytes - Lymphocytes are one of your body's immune type cells seeing lymphocytes invading into the melanoma is a sign your body is able to recognize the melanoma as a problem. The pathologist will comment as absent, brisk or non brisk
- Microsatellites - This refers to whether the pathologist can see little nests of melanoma cells separate from the main spot.
- Perineural invasion - This refers to whether the pathologist can see any melanoma cells in or around the nerves
- Lymphovascular invasion - This refers to whether the pathologist can see any melanoma cells inside the small blood vessels or the lymph vessels
- Ulceration - This refers to whether the melanoma has lost it's external cells layer You might already know this if the lesion has been bleeding or weeping it is likely ulcerated.
- Regression - The pathologist will comment whether it looks as though there may have been melanoma cells once present but have now been destroyed by your immune system. If regression is present it can be very hard to know accurately the true maximum depth of the melanoma
- Associated - The pathologist will comment on whether this melanoma started in a pre existing naevus ( mole )
- Margins - Finally the pathologist will comment how much normal tissue ( marginal tissue) is seen outside the edge of the melanoma.
When the recommendation about the definitive surgery is made surgical margins are a key issue . At the initial biopsy when tissue is being taken to establish the diagnosis it is often the case that the margins are incomplete or minimal . At the biopsy stage we are simply trying to see if the lesion of concern is or isn't a melanoma. Once we have this information a discussion about margins becomes important.
In the next part will explain how we stage melanoma and why it is very important not to confuse the term level with the term stage when we discuss melanoma.
Author:Dr James Burt
About: Dr Jamie Burt was born and educated in Melbourne, attending the University of Melbourne and graduating with MBBS in 1998. He is a member of the Senior Medical Staff at St. Vincent’s Hospital, Melbourne, and was Head of Reconstructive and Plastic Surgery at the Peter MacCallum Cancer Institute until 2004. Known for his respectful, informative, and caring approach, Jamie has been caring for patients for over 15 years. Connect via:LinkedIn