A 23-year-old woman presents to her physician with a nevus on her arm that is asymmetrical with irregular borders. She has noticed a change in the color of this nevus in recent weeks. The nevus is removed and sent to the pathologist. On examination of the specimen, the pathologist determines that it is a melanoma. Which of the following features of this lesion is the greatest indicator of a poor prognosis for this patient?
(A) Depth within the dermis of >2 mm

(B) Growth location on her arm

(C) Lateral spread within the epidermis of >5 mm

(D) Previous basal cell carcinoma lesions

(E) Very large average size of neoplastic cells

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The correct answer is A. In the vertical growth

phase of melanoma, neoplastic cells grow

deeply into the dermis. Considering that invasion

of lymphatics or blood vessels (deep structures)

is necessary for distant metastasis of any

cancer, it can easily be understood why the

depth of invasion is so important in highly labile

melanoma. The depth of invasion into the

dermis is an established prognostic factor for

the patient, since most melanoma patients die

due to complications of metastatic melanoma

involvement of other organs (lung or brain).

Patients with a tumor depth <1.7 mm have a

more favorable prognosis. Remember the ABCDE’s

of melanoma: Asymmetry, Borders (irregular),

Color variation, Diameter >6 mm,

and Elevation/Evolution.

Answer B is incorrect. Location of the lesion

on an extremity, rather than the central body,

indicates a more favorable prognosis.

Answer C is incorrect. Lateral spread within

the epidermis is not as important as depth in

determining metastatic potential.

Answer D is incorrect. Previous lesions do not

have an impact on the likelihood of this nevus

to metastasize.

Answer E is incorrect. Size of neoplastic cells

is not a factor in determining prognosis.