Pathological findings suggestive of interclonal stabilization in a case of cutaneous melanoma.

Metastatic spread is a complex process based on manyfold interactions of the tumor cells with each other and with the surrounding stroma. In experimental systems tumor cell heterogeneity and presence of various subpopulations which interact with one another to stabilize their relative proportions within the population has been shown. Here we report a patient with melanoma, showing morphological evidence of two distinct tumor cell populations in the primary tumor and in all subcutaneous metastases. By image analysis, both populations were clearly characterized by minimal nuclear diameter and by nuclear form factor and were demonstrable in each specimen. The fact that these peculiar cell populations were present in all melanoma lesions removed from the patient might indicate that the populations require the presence of each other and that none of them is metastatically competent on its own.