Worrisome Pigmented Skin Lesion - Nevus or Melanoma
Introduction to pigmented skin lesions
Pigmented skin lesions are the most common skin lesions. Almost everyone have small moles ranging from the size of pin head to that of a dime. However, most of these are not of any dire health consequeses and do not clinically progress during the entire lifetime. Uncommonly and depending on many factors ranging from hereditary to the environmental factors; these may progress in various forms and can transform from the novice looking mole or nevus to a scary looking, noticeable and bothersome entity.
Pigmented lesions arise from the normal constituent of skin cells called melanocytes, which synthesize a brown colored pigment called melanin. There are usually same number of melanocyes in skin irrespective of ethnicity. However, the color of skin depends of the ability of melanocytes to synthesize melanin. Therefore, a caucasian or european individual will have same amount of melanocytes as that of person with African-American decent but will synthesize lesser amount of melanin. Exposure to sunlight or a specific specrum of white light in ultraviolet wavelength range can ehnace the ability of melanocytes to synthesize more melanin (effect seen as tanning). Melanocytes are distributed uniformaly in the lower layers of the skin (see figure). It is when larger number of melanocytes cluster at one location is skin, which forms the pigmented skin lesion visible to an unaided eye. These are then further classified as described in the following section.
Types of pigmented skin lesions (classification)
Most basic classification of skin lesions from the perspective of diagnosis and treatment is whether it is BENIGN (which means that there is nothing to worry about it being life threatening or requiring major surgical and cancer related therapies) or MALIGNANT (which means that the lesion is worrisome, can progress and if not properly or timely treated may result in adverse health consequences). Now I will mention a disclaimer at this point, because almost nothing is perfect in health sciences and unfortunately some of the diseases, including skin, do not read medical books and sometimes follow their own biological evolution. For example an innocuous looking "benign" pigmented skin lesion can enlarge in size, starts to ooze, start feeling itchy or more bumpy and this is the time when it is no more of a beauty spot and it's time to take an urgent trip to your family physician or dermatologist.
Clinical features of benign pigmented skin lesions
Benign pigmented lesions are called in general term as nevus (nevi-pleural). Most of them range from few millimiters to less than a centimeter in size. They can be single or multiple and can be located at any surface lined by skin, including the skin of palms and soles. Nevi can be of different types. Most of them range from light gray to light brown to dark black to dark brown. Some of them can be the shade of light tan green to blue (blue nevus) and few of them can have tan-red color with light skinned rim (also called halo nevus). The color of nevi also depend on the natural background skin color and the amount of melanin that can be produced. Interestingly nevi can occur at locations not covered by skin and this may include scleral surface (white surface of eyes), mucosal membranes located within the mouth (also called buccal mucosa or orophyrangeal mucosa), anorectal mucosal membranes (located at the terminal portion of large intestine), internal organ linings such as parietal peritoneal linings or meninges (covering on brain). Fortunately nevi are rare at the sites other than skin.
Benign lesions do not change in size for years or whole life. They are not sensitive to the heat, pressure or irritation by clothes or touch. The borders are smooth and regular and imperceptably blend with the surrounding normal skin. They do not ooze any fluid and neither do they ulcerate or have any bloody discharge. There is no itching sensation at the benign pigmented lesions. Some of the nevi can have hair and this does not indicate any worrisome change.
In contrast, malignant lesions or melanoma/melanoma-in-situ significantly increase in size over a smaller interval of time (within weeks to couple of months). Are sensitive and itchy to touch and irritation by the clothing, may ooze bloody discharge, have ragged elevated borders, may have smaller pigmented spots around the larger central spot, can ulcerate and can be painful.
In conclusion, it is easy to suspect a malignant pigmented lesion and seek medical help early in the course of progression. Malignant lesions are first biopsied and then resected with wide skin margin. Lymph nodes in the region draining the skin may or may not be sampled based on the clinical and pathological parameters such size and depth of lesion. The condition can be managed with surgery, chemotherapy and radiology based on the extent of disease.