ABSTRACT
BACKGROUND: In primary melanomas, data on the degree of intratumoral heterogeneity to date have been lacking. OBJECTIVE: Our purpose was to investigate intratumoral DNA stem-line heterogeneity in superficial spreading melanoma (SSM). METHODS: Multiple measuring fields of 54 SSMs (tumor thickness median 1.60 mm) were studied by DNA image cytometry to obtain data on the number of DNA stem lines per tumor, their ploidy characteristics, and intratumoral distribution. Results were compared with standard histopathological criteria. RESULTS: Twenty-three of 54 SSMs were found to have two or three distinct proliferating tumor cell stem lines (1.46 +/- 0.57 per tumor). Stem lines appeared spatially separated in 22 of 23 SMMs. At least 3 measuring fields per tumor were necessary to identify all stem lines with a likelihood of 95%. DNA heterogeneity correlated with tumor thickness, but occurred in 5 of 19 cases of pT1 melanoma. CONCLUSIONS: Primary SSMs can be regarded as potentially clonally unstable with a tendency for spatial separation of tumor cell stem lines.
