Quantitative Diffusion-Weighted MR Imaging: Is There a Prognostic Role in Noninvasively Predicting the Histopathologic Type of Uveal Melanomas?

Simple Summary Histologic type is an important prognostic determinant in the clinical workup of uveal melanoma (UM), with different histologic types being related to different metastatic risk and hence mortality rates. The diagnosis of UM is predominantly clinical, whereas biopsy, although capable of providing the histologic type, is not routinely performed due to its invasiveness and complications. Moreover, biopsy often provides contradictory results because of the heterogeneity of UMs. In this context, recently the interest has grown as regards to noninvasive biomarkers, which can represent alternative methods of prognostication. We verified whether magnetic resonance imaging and, in particular, one of its functional techniques, diffusion-weighted imaging, could be helpful in distinguishing the different histologic types of UMs and therefore play a prognostic role. Whilst negative, our preliminary results could represent a starting point for future research in the context of a patient-centered approach of healthcare.Abstract Histopathologically, uveal melanomas (UMs) can be classified as spindle cell, mixed cell and epithelioid cell type, with the latter having a more severe prognosis. The aim of our study was to assess the correlation between the apparent diffusion coefficient (ADC) and the histologic type of UMs in order to verify the role of diffusion-weighted magnetic resonance imaging (DWI) as a noninvasive prognostic marker. A total of 26 patients with UMs who had undergone MRI and subsequent primary enucleation were retrospectively selected. The ADC of the tumor was compared with the histologic type. The data were compared using both one-way analysis of variance (ANOVA) (assessing the three histologic types separately) and the independent t-test (dichotomizing histologic subtypes as epithelioid versus non-epithelioid). Histologic type was present as follows: the epithelioid cell was n = 4, and the spindle cell was n = 11, the mixed cell type was n = 11. The mean ADC was 1.06 +/- 0.24 x 10-3 mm2/s in the epithelioid cells, 0.98 +/- 0.19 x 10-3 mm2/s in the spindle cells and 0.96 +/- 0.26 x 10-3 mm2/s in the mixed cell type. No significant difference in the mean ADC value of the histopathologic subtypes was found, either when assessing the three histologic types separately (p = 0.76) or after dichotomizing the histologic subtypes as epithelioid and non-epithelioid (p = 0.82). DWI-ADC is not accurate enough to distinguish histologic types of UMs.