Tumor angiogenesis is thought to play a major role in determining the biologic behavior of neoplasms, including melanomas. Using immunostaining technology, investigators compared vascularity, tumor cell proliferation, and apoptosis rates in tumor cells from melanoma micrometastases and macrometastases obtained from lymph nodes. Macrometastases were identified on clinical examination. Micrometastases were clinically undetectable and were defined as foci of metastatic disease detected at the time of histologic examination.
The microscopic lesions had significantly fewer surrounding vessels than the clinically apparent lesions did. In contrast, the relative rates of proliferation and apoptosis were similar in the two types of lesions. The investigators conclude that the difference in vascularity may correlate with the difference in biologic behavior of micrometastases and macrometastases and may account for the apparent "dormant" state associated with micrometastases.
Comment: The investigators suggest that a "dormant" state may explain why patients with melanoma may develop metastases up to 40 years after a primary diagnosis, and that a balance of proliferation and apoptosis, controlled in part by low vascular supply, may account for this finding. These observations and the authors' analyses provide interesting new insights into the enigmatic behavior of some melanomas. It remains to be seen whether the observations will hold up to careful prospective study and will ultimately provide clinicians with prognostic information.
Published in Journal Watch Dermatology October 1, 1998
Barnhill RL et al. Tumor vascularity, proliferation, and apoptosis in human melanoma micrometastases and macrometastases. Arch Dermatol 1998 134 991-995.
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