Anatomic site of primary melanoma is associated with depth of invasion.

BACKGROUND

The prognosis of melanoma is correlated to the stage of the primary lesion. Tumor site has also been implicated, with locations such as the trunk carrying a worse prognosis than others (such as limbs).

HYPOTHESIS: To determine if tumor thickness correlates with location in a nonvisible body area.

DESIGN AND

SETTING

Retrospective medical record review of all patients with stage I melanoma treated in our medical center between 1986 and 1994. Demographic data as well as primary tumor characteristics were recorded.

METHODS

The skin's surface was divided into occult and exposed areas. Exposed indicated visible to the patient during routine activities; occult areas included posterior aspect of the neck, back, posterior aspect of the thigh, calf, and plantar region. Data were analyzed for significance using the chi2 test.

RESULTS

Of the 178 patients with stage I melanoma analyzed, 51.1% had limb, 35.9% trunk, and 12.9% head and neck lesions. Depth of invasion was less than 0.76 mm in 32.6%, 0.76 to 1.5 mm in 25.2%, and more than 4 mm in 7.9%. In 87 patients the tumor occurred in occult areas and in 91 patients in exposed areas. Comparing the depth of invasion in these 2 groups disclosed that thin (<0.76 mm) melanomas occurred in 20.7% of occult areas compared with 44% of exposed areas (P<.05). Deeper melanomas (>2.50 mm) occurred in 28.7% of occult areas compared with 12.1% of exposed areas (P<.05).

CONCLUSIONS

Tumors in less-visible body areas are significantly thicker at the time of diagnosis than those occurring in more highly visible areas. Delayed detection may be responsible for this finding.