The natural history of malignant melanoma of the choroid: small vs large tumors.

The evidence provided by previous studies of malignant melanomas of the choroid has indicated that a small melanoma is most likely a spindle cell tumor, evolving in a relatively benign growth pattern. However, this generalization has not been tested with regard to the small melanomas which can be considered for conservative management. We have studied 264 malignant melanomas of the choroid; 50 of these were designated as small melanomas (less than 10 mm in diameter and 3 mm in elevation). We found a surprisingly large percentage (22.0%) of mixed andepithelioid tumors (considered to be more malignant) in the group of small tumors. In 33 patients with a possible five-year survival, two (6.1%) died of metastases. Of 22 possible ten-year follow-ups, five patients died of metastatic melanoma (22.7%). These deaths occurred in one patient with a spindle cell A melanoma, three with spindle cell B melanomas, and one with a mixed melanoma. All five of these patients were women, and all had posterior pole tumors. No deaths occurred in patients with tumors less than 7 mm in diameter and 2 mm in elevation. The relatively good five-year survival in the patients with smaller melanomas supports the views held by previous authors that small melanomas carry a better prognosis than larger tumors. However, mixed and epithelioid tumors in our series do not seem to have a worse prognosis than spindle cell tumors. Cell type may be of less prognostic significance than tumor size in the case of small melanomas.