Test your medicine knowledge with the MKSAP challenge, in partnership with the American College of Physicians.
A 50-year-old man is evaluated for a firm, darkly pigmented papule on his back that has been growing steadily over a period of several months. His medical history is unremarkable, and he takes no medications.
On physical examination, vital signs are normal. The skin lesion is a 0.5-cm darkly pigmented, raised plaque with irregular borders and inconsistent coloration. The remainder of his physical examination, including the rest of his skin examination, is unremarkable.
A skin biopsy is performed and shows malignant melanoma on pathologic examination.
Which of the following is the primary feature used to determine prognosis?
A. Lesion depth
B. Mitotic rate
C. Presence of ulceration
D. Radial diameter of the lesion
MKSAP Answer and Critique
The correct answer is A. Lesion depth.
The depth of invasion (Breslow depth) of a melanoma is the most important prognostic feature and correlates most strongly with the risk of recurrence and metastasis. The 2009 American Joint Committee on Cancer (AJCC) staging system defines the primary tumor stage based on the Breslow depth, with 10-year survival rate decreasing progressively with increasing depth.
Other features have also been identified as secondary negative prognostic indicators, including an elevated mitotic rate (defined as more that 1 mitotic figure per mm2) and the presence of ulceration. The presence or absence of these two factors are used to subdivide the tumor stages based on depth into further prognostic categories
The radial diameter of the lesion has not been found to correlate with prognosis; many melanomas are quite wide, and yet if they have not developed an invasion component, the risk of metastasis is very small.
Key Point
- The Breslow depth (or depth of invasion) of a melanoma is the most important prognostic feature and correlates most strongly with the risk of recurrence and metastasis.
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