Histopathology, morphometry, and nuclear DNA content of iris melanocytic lesions.

PURPOSE To compare the histologic, morphometric and nuclear DNA content of a group of benign and malignant melanocytic lesions of the iris. METHODS Forty-four surgically excised melanocytic lesions of the iris were histologically classified as nevus or melanoma. Morphometric analysis using a digital filar micrometer (LaSICO 1602N-10 and 5-4A) measured the mean size of the 10 largest nucleoli, and Feulgen staining and image cytometry (CAS 200 Cell Analysis Systems) analyzed the nuclear DNA ploidy in the lesions. Patient follow-up information was obtained whenever possible. RESULTS Sixteen cases were histologically classified as nevi and twenty-eight cases as melanoma. The mean of the 10 largest nucleoli of the nevi was smaller than the mean among the melanomas (1.772 microns [SD = 0.366] and 2.773 microns [SD = 0.565], respectively). Feulgen staining revealed that all lesions were diploid, with the exception of two hyperdiploid and two hypodiploid melanomas. Of the patients with follow-up information available, none with nevi developed a metastasis and two with melanoma died of metastatic disease. CONCLUSIONS The histologic classification of iris melanocytic lesions (i.e., nevus versus melanoma) correlates to nucleolar size (P < 0.001) but not to nuclear DNA ploidy.