Abstract

Ciliation index (CI) is defined as the percentage of lesional cells with a primary cilium ‎‎(PC), a ubiquitous organelle found on the apical surface of almost all cell types.1 Low CI has ‎been demonstrated in in several melanomas, but their retention has not been studied in nevoid ‎melanoma and PRAME-negative or –indeterminant melanoma.2-7 Fluorescent ‎immunohistochemistry (IHC) was done in 9 nevoid melanomas and 8 mitotically active ‎melanocytic nevi, as well as 4 PRAME-negative melanomas, 4 PRAME-indeterminant ‎melanomas, 5 PRAME-positive melanomas, and 3 PRAME-negative benign melanocytic nevi. ‎
The CIs were compared using an independent t-test. Low CI was demonstrated in all 4 nevoid ‎melanomas relative to mitotically active melanocytic nevi, as well as in all but one PRAME-‎negative melanoma and the PRAME-indeterminant melanomas relative to benign melanocytic ‎nevi. These suggest that CI can be a helpful adjunct to distinguish nevoid melanoma from ‎mitotically active nevi, and when the histopathology and PRAME IHC results are not ‎congruent.‎