Distinguishing cellular blue nevi (CBNs) and atypical CBNs from blue nevus-like melanoma (BNLM) can be diagnostically challenging. Immunohistochemistry may inform the diagnosis in a subset of cases but is not always diagnostic. Further, ancillary molecular testing is expensive and often requires significant tissue to complete. Primary cilia are cell-surface organelles with roles in signal transduction pathways and have been shown to be preserved in conventional melanocytic nevi but lost in melanoma. Immunofluorescence staining of primary cilia can be performed using a single standard-thickness formalin-fixed paraffin-embedded tissue section and has a turnaround time similar to immunohistochemistry. The percentage of tumoral melanocytes retaining a primary cilium is quantified and reported as the ciliation index. In the current study, we explored the utility of the ciliation index in a series of 31 blue nevus-like lesions, including CBNs (12), atypical CBNs (15), and BNLM (4). The average ciliation index for the CBNs was 59±18%, with a median of 60 (range: 28 to 87). The average ciliation index for atypical CBNs was 59±23, with a median of 59 (range: 20 to 93). The average ciliation index for BNLM was 4±3, with a median of 3 (range: 1 to 8). There was no significant difference in ciliation index between the CBN and atypical CBN categories. There was a significant difference between CBN and BNLM and between atypical CBNs and BNLM (P<0.001 for each). Here, we show that ciliation index is a quantitative diagnostic tool useful in the setting of blue nevus-like neoplasms, with benefits including cost and time efficiency.

中文翻译：

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细胞性蓝痣和非典型蓝痣中初级纤毛得以保留，而蓝痣样黑色素瘤中初级纤毛消失。

区分细胞性蓝痣 (CBN) 和非典型 CBN 与蓝痣样黑色素瘤 (BNLM) 在诊断上可能具有挑战性。免疫组织化学可以为部分病例提供诊断信息，但并不总是具有诊断意义。此外，辅助分子测试非常昂贵并且通常需要大量组织才能完成。原发纤毛是在信号转导途径中发挥作用的细胞表面细胞器，并已被证明在传统黑素细胞痣中得以保留，但在黑色素瘤中丢失。初级纤毛的免疫荧光染色可以使用单个标准厚度的福尔马林固定石蜡包埋的组织切片进行，并且具有与免疫组织化学相似的周转时间。保留初级纤毛的肿瘤黑素细胞的百分比被量化并报告为纤毛指数。在当前的研究中，我们探索了纤毛指数在一系列 31 个蓝痣样病变中的效用，包括 CBN (12)、非典型 CBN (15) 和 BNLM (4)。CBN 的平均纤毛指数为 59±18%，中位数为 60（范围：28 至 87）。非典型 CBN 的平均纤毛指数为 59±23，中位数为 59（范围：20 至 93）。BNLM 的平均纤毛指数为 4±3，中位数为 3（范围：1 至 8）。CBN 和非典型 CBN 类别之间的纤毛指数没有显着差异。CBN与BNLM之间以及非典型CBN与BNLM之间存在显着差异（均P<0.001）。在这里，我们证明纤毛指数是一种可用于蓝痣样肿瘤设置的定量诊断工具，具有成本和时间效率等优点。