Risk factors identified for transformation of eye growths into melanoma

Eight factors may predict whether a choroidal nevus – a benign, flat, pigmented growth inside the eye and beneath the retina – may develop into melanoma, according to a report in the August issue of Archives of Ophthalmology, one of the JAMA/Archives journals.

"There is strong interest for early detection of choroidal melanoma [a malignant growth], and its differentiation from nevus continues to be the major impediment," the authors write as background information in the article. Benign choroidal nevi and small melanomas share many characteristics, including color, location and size. "The challenge is to identify the single small melanoma among the thousands of choroidal nevi. It has been estimated that 6 percent of the white population harbors a choroidal nevus and that one in approximately 8,000 of these nevi transform into melanoma."

Carol L. Shields, MD, and colleagues at Wills Eye Institute, Thomas Jefferson University, Philadelphia, studied the medical records of 2,514 consecutive eyes of patients with choroidal nevi between 1974 and 2006. The tumours had a median (midpoint) diameter of 5 millimetres and a median thickness of 1.5 millimeters at the beginning of the study. Choroidal nevi grew into melanoma in a total of 180 eyes (7 percent) over an average follow-up of 53 months, including 2 percent after one year, 9 percent after five years and 13 percent after ten years.

The factors that predicted growth into melanoma included five previously identified factors: tumour thickness greater than 2 millimetres, fluid beneath the retina, symptoms such as decreased vision or flashes and floaters, orange pigment and a tumour edge within 3 millimetres of the optic disc. Two new factors were also identified: hollowness of the growth on ultrasound and the absence of a surrounding halo, or circular band of depigmentation.

"Until systemic therapies for metastastic uveal melanoma improve, our focus should be on early detection to minimise metastastic disease," the authors write. "All ophthalmologists should participate in this effort and patients with risk factors can be referred for evaluation at centres familiar with the nuances in the diagnosis and management of early melanoma."

(Source: JAMA/Archives: Archives of Ophthalmology: August 2009)