Melanoma Basics
What is a "lentigo maligna melanoma"?
There are multiple different types of malignant melanoma that we distinguish both in their clinical presentation as well as how they look under the microscope. One of these is an entity called lentigo maligna melanoma. This is also known as the malignant freckle. The important part of a lentigo maligna is that they grow horizontally for a long period of time meaning they get bigger in diameter for a long period of time. Their invasiveness only comes after potentially years of growth. Although they are significant, as they grow horizontally they are not a biological threat to the patient. So, we have a long time to recognize their presence and therefore, ample opportunity to remove them before they become aggressive and have any chance of metastasis. The lentigo malignas occur primarily in the elderly and almost always on heavily sun-exposed areas such as the back of the hands, the arms and the scalp.
What is an "acral lentiginous melanoma"?
There are numerous different types of malignant melanomas that we can define, based on where they are located, their nature as they present to the doctor, and also on features under the microscope. One type of this malignant melanoma is a type of melanoma called a acral lentiginous malignant melanoma. These are the most rare form of malignant melanoma. It is found under the fingernails and toenails, on the bottom of the feet and on the palms. It is the most common type of melanoma that presents in people of pigment (blacks and Asians), however it is rare in the Caucasian population. Acral lentiginous melanoma is often very difficult to diagnose, as they are neglected areas of exams sometimes, and tend to present at somewhat later stage. Due to this acral lentiginous melanoma have on presentation a greater chance of metastasis. They are identifiable, however, and can be seen and biopsied, and found earlier so that their risk to the patient is minimal.
What is "nodular melanoma"?
There are many different subtypes of melanomas that patients can present with at the doctor's office. They are dictated by their location on the skin, and the nature of how they look clinically, as well as how they are under the microscope. The most dangerous type of malignant melanoma skin cancer is the “nodular melanoma,” which accounts for approximately 15% of all melanomas. Nodular melanomas have a very short or absent horizontal growth phase, which means that they grow horizontally for a very short time before they start growing vertically or invasively. The chance of metastasis increases the more invasive the melanoma cells are in the dermis. These lesions present with an already high risk of metastasis when they first show at the doctor's office. Often these lesions are also non-pigmented, and in being so are very difficult to distinguish from other lesions on the skin.
What is a "superficial spreading malignant melanoma"?
The most common type of malignant melanoma, which occurs in seventy percent of all malignant melanomas, is the superficial spreading malignant melanoma. That malignant melanoma, fortunately, has a very long, horizontal growth phase. The horizontal growth phase is where the cells, the atypical cells, grow in the epidermis and make the malignant melanoma broader or wider. Under those circumstances, when that lesion can be found, it is a hundred percent curable by removing the melanoma. After some time however, that horizontal growth phase stops or is replaced by a vertical growth phase, whereby the cells start growing into the dermis. The more invasive those cells are into the dermis, the more likely those cells have an opportunity to have access to the blood vessels and the lymphatics and to spread to other organs in the body. That can be a fatal event.
Where else in the body does melanoma generally spread?
Malignant melanoma is generally localized to the skin. It's under those circumstances when we remove it that there is a one-hundred percent cure. However, in certain cases when the melanoma cells have invaded deeper into the dermis, it has access to the lymphatics and to the blood vessels and can spread to other organs. Some of the organs that it can spread to and the most likely are to the regional or draining lymph nodes. That is something that can be both palpable and felt when it does so or it could be investigated by a very special surgical technique called a sentinel lymph node biopsy. Another place where the cells may be lodged is in the skin close to the original melanoma on the way to those regional lymph nodes. When melanoma does have access though to the body in general it can metastasize to skin in distant sites, as well as to the lungs, the brain, and some of the other visceral organs as well.