Comparison of current methods and PCR for the diagnosis of metastatic disease in uveal malignant melanoma.

The most common intraocular malignancy in adults is the uveal melanoma. Thirty to fifty percent of patients die of systemic metastatic disease within 5 years of follow-up [1]. Reliable data of the metastatic disease before treatment is important to determine the influence of local therapy on overall survival rates. Analysis of 700 patients after globe-preserving therapy of uveal melanoma showed that the choice of treatment had little overall influence on survival rates [2], which might be due to pretreatment dissemination that was not detected with current methods for the diagnosis of metastatic disease. We examined 12 patients with uveal melanoma for circulating melanoma cells using PCR amplification of gene transcripts for tyrosinase [3, 4]. Chest x-ray, serum liver enzyme determination, liver scan, bone scan, computer tomography of the head and magnetic resonance images were negative in all patients. In samples of 2 out of 12 patients (16.6%) a band with the expected size (207 bp) was detected after gel electrophoresis indicating the presence of circulating melanoma cells. In 1 of these patients enucleation was performed, because of the ‘ringtype’ growth of the tumor. Histopathologically, invasion of a vortex vein was noted. In addition, invasion of the inner layers of the sclera was observed. In the second patient with evidence of circulating melanoma cells, a histopathological examination was not possible due to globe-preserving treatment using Gamma Knife therapy. This patient developed liver metastasis within the following 12 months. None of the other patients has developed metastatic disease up to now. Due to the small number of patients included in this study these findings have to be evaluated carefully. Nevertheless, even though it is known that the detection of melanoma cells in blood cannot automatically be taken as a definitive sign for the presence of metastatic disease, RT-PCR might help interpreting the result of conventional markers for metastasis in the near future.