DNA ploidy pattern in choroidal melanoma: correlation with survival. A flow cytometry study on archival material

Background/aims - Paraffin samples have provided an important source of mat erial for retrospective cytofluorimetric studies, useful in establishing th e predictive value of DNA content measurements. The aim of this study was t o investigate the incidence and type of aneuploidy in choroidal malignant m elanomas (CMM) and the significance in the clinical outcome (median follow up 55 months). Methods - DNA content was quantified by flow cytometry in 61 CMM from archi val material. Non-tumour ocular tissue was used as the reference diploid st andard. Cases in which the coefficient of variation (CV) of the diploid pea k was >8% were excluded. The CMM were classified as spindle A, spindle B, m ixed spindle and epithelioid, epithelioid, and necrotic. Results - The frequency of the aneuploid DNA pattern was 38%. Necrotic tumo urs showed a worse clinical outcome independent of the ploidy pattern. Spin dle A tumours were found to be diploid. Spindle B and mixed tumours showed a prevalent diploid and near diploid aneuploid pattern (DI < 1.3), yet aneu ploidy was not correlated with a worse prognosis. The epithelioid tumours w ere prevalently diploid. However, 83% of the aneuploid tumours were hypodip loid (DI < 0.95), and showed the worst prognosis. Conclusion - These results indicate that increasing DNA abnormalities in CM M, especially in the epithelioid histotype, were associated with an increas ing mortality.