Melanoma



Melanoma


William P. Reed



Dennis O’Shea is a 45-year-old executive who undergoes a shave biopsy of a mole on the upper part of his right back. He has always had numerous moles scattered over his back and chest but never paid them much attention until his wife noted that one had become somewhat larger than the rest. The pathology report on tissue submitted at the time of the shave biopsy shows a tan to dark brown piece of skin measuring 9 × 5 mm. Microscopic examination shows a benign Spitz nevus extending to the margins of the specimen. Considering the benign nature of the lesion, he is advised that no further therapy is warranted at this time. He seeks a second opinion because several members of his family have died of cancer, and he is concerned that this may be an early sign of malignancy. During physical examination, Mr. O’Shea appears to be a healthy, tanned white man with sandy hair and blue eyes. His vital signs are normal. His lungs are clear. The heart sounds are normal, with no murmurs. His abdomen shows no scars or masses. There is no lymphadenopathy. There is a recent scar over the right scapula that is slightly reddened, with a suggestion of darker pigmentation at the medial margin. He has freckles on the tops of his shoulders and numerous benign-appearing moles scattered over his torso and extremities.



Given this presentation, what is the initial clinical impression?

View Answer

Any change in a mole or pigmented lesion should be assumed to be malignant melanoma until proven otherwise.



Doesn’t the diagnosis of a Spitz nevus prove that this is not a melanoma?

View Answer

The Spitz nevus has many features in common with melanoma (1, 2, 3). Often, the distinction is made on the basis of microscopic features at the depths of the lesion or on the basis of the clinical features. The Spitz nevus tends to be less than 6 mm in diameter, symmetric, and uniform in color, with a progressively benign appearance of cells on histologic examination (maturation) as the deepest margin of the lesion is approached. In contrast, melanoma presents with the distinct features of asymmetry, border irregularity, color variegation, and diameter greater than 6 mm (the so-called ABCDs of melanoma). Histologic examination of the lesion shows invasion at the deepest portion.



What is the origin of melanoma?

View Answer

Melanoma develops from melanocytes, which are pigment-producing cells derived from the neural crest that migrate during fetal development into the skin, eye, central nervous system, and mucous membranes. The most common site of melanoma is the skin, but these tumors can develop in any tissue that contains melanocytes. This cancer comprises 3% to 4% of malignancies, with 55,000 new cases each year in the United States (4). From the 1930s to the mid-1980s, there was a rapid rise in the incidence of this disease, doubling every 10 years (5). Epidemiologic studies from 1995 suggested that the incidence was leveling off in susceptible populations. Perhaps this reflects better attention to preventive measures as the causation becomes clearer (6).



What is the cause of melanoma?

View Answer

The direct cause is unknown, but there is considerable evidence to suggest that ultraviolet light is the principal carcinogen. Susceptible people are those with pale complexions and reddish hair who are most prone to skin injury upon exposure to sunlight. An inverse relationship between latitude and incidence of disease has been noted for such people both in Australia and in North America. Melanoma most commonly occurs on the skin that is left uncovered, such as the back and chest in men and the arms and legs in women.



Is there a gender or race predilection for malignant melanoma? Do these groups differ in prognosis?

View Answer

A survey of more than 8,500 malignant melanoma patients revealed a slight predominance in men (52%) over women (48%) with regard to the total number of cases reported (7). With regard to race, 98% of this group were white. In general, women tend to have a longer survival time than men. In blacks, malignant melanoma tends to occur on the palms of the hands, the soles of the feet, or beneath the nail plate; it tends to exhibit an aggressive growth pattern and early metastasis with a poor overall prognosis. The 5-year survival in the black population has been estimated to be as low as 23% (8).



Is there a difference between genders in the anatomic location of malignant melanoma? Does the location of pigmented lesions offer any prognostic information?

View Answer

Different patterns of sun exposure lead to a significant difference between men and women with respect to body location of melanoma. Men tend to have more lesions on their trunks, whereas women have more extremity lesions, particularly on the lower limbs. Melanomas in women tend to be thinner, with less tendency to ulcerate. It is unknown whether this is an inherent feature of the location or is due to easier detectability. As a result, regional lymph node involvement and distant metastases occur less often in women than in men. Therefore, men with a predominance of trunk lesions have a relatively poor prognosis, whereas women with a predominance of extremity lesions have a relatively good prognosis (5).



Are there any precursor lesions of melanoma?

View Answer

Yes. The dysplastic nevus syndrome is familial and is believed to be a precursor of malignant melanoma. This syndrome follows a familial pattern and is characterized by a large number of irregularly shaped nevi on the trunk. Those with dysplastic nevus syndrome are believed to have a cumulative lifetime risk of melanoma approaching 100% (9). Giant congenital nevi in children are believed to be premalignant, with a risk of malignancy reported to be as high as 40%.



What specific changes in nevi indicate the need for biopsy?

View Answer

Any change in size, shape, or color of a nevus, as well as any itching, ulceration, or bleeding, suggests that biopsy should be considered. Changes in size and shape occur in approximately 70% of melanomas. The change in color is usually toward increasing pigmentation; however, amelanotic melanomas do exist. In addition, pigment may fade in some areas (regression) while deepening in others. Ulceration and bleeding are late signs that usually indicate deeply invasive disease (10).



What are the histologic types of cutaneous melanoma? Which have the overall best prognosis and worst prognosis? Which is the most common type?

View Answer

The histologic types of melanoma and their approximate incidences are as follows: superficial spreading (70%), lentigo maligna (5%), acral lentiginous (10%), and nodular (15%). Both lentigo maligna and superficial spreading melanomas have a relatively good prognosis if they are diagnosed early. These types of melanoma have a predominant horizontal growth pattern such that the melanocytes proliferate superficially along the epidermal-dermal junction and only later become locally invasive. For patients with these types of melanoma, changes in size, shape, or color can be detected while the tumor is locally noninvasive.

Acral lentiginous tumors, which develop on the palms and soles or beneath the nails, also have a prominent horizontal growth component, but they are a bit more invasive than the superficial types. These lesions, which are more common in African Americans (70% of melanomas) and Asians, present late and carry a worse prognosis. Nodular melanoma develops early deep invasion and tends to metastasize early. This type of melanoma most often presents as a uniform pigmented nodule, but 5% will be amelanotic.

Nodular melanoma carries the worst prognosis.



What is the difference between an incisional and excisional biopsy?

View Answer

An incisional biopsy entails removal of only a portion of the lesion. The size of the incision varies, but the specimen must be large enough to permit an adequate diagnosis. It is best to include the most raised area of the lesion to allow adequate microstaging. An excisional biopsy entails removal of the entire lesion, leaving only normal tissue at the excised wound edge.



Should an incisional or excisional biopsy be performed?

View Answer

When possible, an excisional biopsy is performed. In some areas, such as the face or scalp, excision may not be cosmetically acceptable until a diagnosis of malignancy is established. Incisional biopsy is used in these cases for initial histologic examination. Incisional biopsy may also be appropriate for large lesions where grafting will be needed for closure.

Punch biopsy can provide a full-thickness sample without the need for suture closure. These biopsies are obtained from the thickest area of the lesion. It is not necessary to obtain normal surrounding skin. Superficial skin biopsy by shaving should never be used when melanoma is the suspected diagnosis because this technique may not provide a specimen that is deep enough to extend into the tumor proper. Not only will the diagnosis be missed in such cases, but the partial removal of the upper layers of tumor may interfere with microstaging on subsequent excision.



Why is an excisional biopsy preferable?

View Answer

An excisional biopsy is preferable because it provides the pathologist with the entire lesion. This allows the deepest extent of the tumor to be determined for microstaging purposes (discussed later). Sometimes, an incisional biopsy permits only a histologic diagnosis and not an accurate determination of the depth of invasion. In addition, excision with adequate margins may obviate further intervention when a thin melanoma or preinvasive lesion is encountered. When an incisional or punch biopsy is used, it should be obtained from the most raised portion of the lesion. This will provide the greatest chance of determining depth of invasion, which in turn determines the ideal margins for excision. When the clinical appearance leaves little doubt about the diagnosis, punch biopsy allows histologic confirmation and staging with minimal disruption of lymphatics for later nodal mapping by lymphoscintigraphy.

Mr. O’Shea notes some itching in addition to the change in size and shape of his mole. When he scratches the mole, occasionally it bleeds.



What should the next step be in the management of Mr. O’Shea’s mole?

View Answer

The remaining lesion should be excised.

Biopsy results show a melanoma invasive into the reticular dermis. The thickness of the lesion is 0.95 mm. The melanoma is on the epidermal surface in some areas, suggesting ulceration.



How are melanomas staged clinically? What is Mr. O’Shea’s stage?

View Answer

Melanoma is staged as follows (11); see also Table 28.1:



  • Stage I: local to the upper (superficial) dermis


  • Stage II: local to the lower (deep) dermis or subcutaneous tissues


  • Stage III: regional metastases, either to lymph nodes or to intralymphatic spaces (satellitosis or in-transit metastases)


  • Stage IV: distant metastases are present








TABLE 28.1. Stage Groupings for Cutaneous Melanoma








































































































































































































Clinical Staging


Pathologic Staging



T


N


M


T


N


M


0


Tis


N0


M0


Tis


N0


M0


IA


T1a


N0


M0


T1a


N0


M0


IB


T1b


N0


M0


T1b


N0


M0



T2a


N0


M0


T2a


N0


M0


IIA


T2b


N0


M0


T2b


N0


M0



T3a


N0


M0


T3a


N0


M0


IIB


T3b


N0


M0


T3b


N0


M0



T4a


N0


M0


T4a


N0


M0


IIC


T4b


N0


M0


T4b


N0


M0


III


Any T


N1


M0







N2








N3






IIIA





T1-4a


N1a


M0






T1-4a


N2a


M0


IIIB





T1-4b


N1a


M0






T1-4b


N2a


M0






T1-4a


N1b


M0






T1-4a


N2b


M0






T1-4a/b


N2c


M0


IIIC





T1-4b


N1b


M0






T1-4b


N2b


M0






Any T


N3


M0


IV


Any T


Any N


Any M1


Any T


Any N


Any M1

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Sep 23, 2016 | Posted by in UROLOGY | Comments Off on Melanoma
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