Uveal melanoma: An analysis of cellular features and comparison to monosomy 3 status

Background Choroidal and ciliary body melanomas divide into two approximately equal groups. Local therapy cures one group while the other metastasizes and proves lethal. Monosomy 3 strongly associates with aggressive behavior. We analyzed a series of choroidal and ciliary body melanomas to describe the cellular features and to compare them to monosomy 3 status using the latter as a surrogate for survival. Methods One hundred eleven specimens met the study's inclusion criteria. Following ThinPrep processing, samples were analyzed for cellular features including: cell type, nuclear grade, tumor infiltrating lymphocytes, and the presence of necrosis and melanin. FISH analysis for monosomy 3 was performed on ThinPrep slides using a threshold of 20% monosomic cells per 200 melanoma cells. Results Seventy‐two tumors (65%) had a mixed cell type while spindle cell type and epithelioid cell type occurred in 37 (33%) and 2 (1.8%), respectively. Seventy‐five tumors (68%) had Grade 2 nuclear atypia. Monosomy 3 occurred in 57 tumors (51%). Significantly more tumors with Grade 3 nuclei had monosomy 3 (79% vs.43%, P  = 0.002) and metastases (29% vs. 8%, P  = 0.01). None of the 11 pure spindle cell tumors with Grade 1 nuclei metastasized or had monosomy 3. Conclusions Uveal melanoma has a relatively consistent cellular appearance, characterized by a mixed cell pattern and no more than moderate nuclear atypia. This consistent appearance aids in the cellular diagnosis but limits prognostication using cellular features. Cellular features significantly associate with monosomy 3 status only in the minority of tumors at the extremes of the morphologic spectrum. Diagn. Cytopathol. 2016;44:377–383. © 2016 Wiley Periodicals, Inc.