Melanoma Lecture Notes PDF

Melanoma Melanoma is uncommon, but not rare. Individuals born today are estimated to have roughly a 1 in 75 lifetime risk of developing a melanoma. Melanoma is related in some way to sun exposure, as individuals who live near the equator are at higher risk than similar people living at higher latit...

Melanoma Melanoma is uncommon, but not rare. Individuals born today are estimated to have roughly a 1 in 75 lifetime risk of developing a melanoma. Melanoma is related in some way to sun exposure, as individuals who live near the equator are at higher risk than similar people living at higher latitudes. However, the exact type of sun exposure (cumulative exposure vs. intermittent burns, UVA vs. UVB) that increases risk is not known. Sunscreen use has very recently been shown to decrease melanoma risk. Melanoma is also more common in lightly pigmented individuals and in individuals with many moles. Family history is also important, as family history of melanoma is a definite risk factor. At especially high risk are families in which members have large numbers of atypical looking nevi and most family members have had a melanoma – the families are said to have the “Dysplastic Nevus Syndrome”. However, having even one first degree relative with melanoma increases the risk of melanoma for a given individual. Melanoma is divided into four types: superficial spreading, nodular, acral, and lentigo maligna. Superficial spreading melanoma is the most common type. It presents as a flat, irregularly pigmented macule or thin plaque. (Figure 8.1) (Figure 8.2) (Figure 8.3) (Figure 8.4) (Figure 8.5) Nodular melanoma is the second most common type. Nodular melanomas are clinically raised lesions. They are often ulcerated. (Figure 8.6) (Figure 8.7) (Figure 8.8) Superficial spreading and nodular melanomas can occur anywhere on the body, including the scalp, perianal or genital area, under the fingernails, in the mouth, or on the ocular conjunctiva, but are by far most commonly seen on the trunk and proximal extremities. Men have more melanomas on the upper back, and women have more melanomas on the lower legs. Acral melanomas are typically flat, brown to black lesions on the palms and soles. (Figure 8.9) Lentigo maligna melanomas develop on extremely sun damaged skin in elderly patients, most commonly the face. They are usually brown, not black. They essentially have the appearance of a very large lentigo (age spot) with irregular of pigmentation. (Figure 8.10) (Figure 8.11) The same features that make a mole atypical are the features of a melanoma. The difference is that the features are typically more pronounced in a melanoma. ABCDE’s of Melanoma: Asymmetry: A melanoma is usually very asymmetrical, with one side being very different from the other. This differs from atypical nevi, which may be asymmetric, but the two different halves are still somewhat similar to each other. Border: A melanoma will often have a very sharp but irregular border. Most nevi, even atypical nevi, have less sharp borders that are relatively regular. Color: A melanoma usually has areas that are black, blue, or gray. These colors are particularly worrisome. However, a melanoma may have only multiple different shades of brown. Color is probably the single most useful feature for identifying lesions concerning for melanoma. Size (Diameter): Most melanomas are over 5 mm in diameter. This is probably the least useful feature, since melanomas can be less than 5 mm and nevi can be greater than 5 mm. Change (Evolution): If the patient is aware of the lesion, they will almost always have noted that a melanoma has been changing in color, size, etc., while it is relatively rare for a nevus to change. Change is the overall most concerning feature in a melanocytic lesion, and changing lesions should almost always be biopsied, regardless of their overall appearance. The Ugly Duckling Rule: If a patient has many moles, most of the moles will usually have similar characteristics – similar sizes, similar colors, similar borders, etc. If one or two lesions are significantly different (“ugly ducklings”), they should be biopsied, even if the features of the lesion(s) are not particularly concerning for melanoma. Special mention should be made of subungual melanomas (under the fingernail or toenail). These lesions look very similar to a subungual hematoma that occurs when there is bleeding under the nail secondary to trauma. However, subungual hematomas should grow out with the nail, with new normal nail appearing proximally over 1-2 months, while a subungual melanoma will not grow out. In addition, if the color extends beyond the nail, onto the skin around the nail, this is extremely concerning and the patient should be sent for a biopsy immediately. The best known genetic alteration in melanoma is mutation of the CDKN2A gene, which encodes two proteins: p16 (involved in Rb pathway) and p14ARF (involved in p53 pathway). When a melanoma is suspected, the entire visible lesion should be surgically removed and sent for pathology. The goal at this point is to remove the entire lesion without removing any additional normal skin. The pathologist will determine if the lesion is a melanoma. If so, the pathologist will also measure how deeply the melanoma extends into the skin. The prognosis is extremely dependent on how thick the initial melanoma is: Melanoma in situ (limited to epidermis): 100% cure rate with complete excision. Extends 1 mm or less into the dermis: 10 yr survival: 90% Extends 1-2 mm into the dermis. 10 yr survival: 80% Extends 2-4 mm into the dermis. 10 yr survival: 60% Extends 4 mm or more into the dermis. 10 yr survival: 50% In addition to depth, the other important characteristic of the tumor is whether or not the surface is ulcerated. If the surface is ulcerated, the survival drops significantly. Regardless of the depth or ulceration, once the original tumor has metastasized (most commonly to the regional lymph nodes initially), the prognosis is extremely poor. When a melanoma is ≤1 mm deep, complete excision of the melanoma is the only treatment required. Patients should be followed closely, as they are at risk for developing a second melanoma. In addition, a review of systems should be done at each follow-up visit. No imaging or bloodwork is necessary, although some physicians check chest x-rays and serum LDH levels. If the melanoma is >1 mm in depth, in addition to complete excision of the lesion and close follow-up of the patient, it is important to determine if lymph nodes are involved. If there is a palpable regional lymph node, it should be biopsied. If there are no palpable lymph nodes, the current recommendation is that the patient undergoes a sentinel lymph node biopsy (SLNB). The initial removal of the melanoma is called the primary excision, and the goal of the primary excision is to obtain a diagnosis and determine the depth of the melanoma. After the melanoma is diagnosed and its depth is determined, the melanoma is re-excised. The goal of the re-excision is to make certain that the entire melanoma is removed (completely excised). To do this, a rim of normal skin is removed from around the primary excision site. The size of the rim of normal tissue is determined by the stage of the primary melanoma. Melanoma in situ or