Background

Errors in Breslow thickness reporting can give misclassification of T category, an important classifier in melanoma staging.

Objective

We sought to investigate precision (number of digits) and terminal digit clustering in Breslow thickness and potential consequences for T category.

Methods

All first primary and morphologically verified invasive melanomas in Norway between 2008 and 2015 were included. A smoothing model was fitted to estimate the underlying Breslow thickness distribution without digit clustering.

Results

Thickness was reported for 13,057 (97.5%) patients; the median was 1.0 mm (range, 0.09-85). It was reported as whole numbers (15.6%), to 1 decimal (78.2%) and 2 decimal places (6.2%)—thin tumors with more precision than thick tumors. Terminal digit clustering was found with marked peaks in the observed frequency distribution for terminal digits 0 and 5, and with drops around these peaks. Terminal digit clustering increased proportions of patients classified with T1 and T4 tumors and decreased proportions classified with T2 and T3.

Limitations

Breslow thickness was not reported in 2.5% of cases.

Conclusions

The Norwegian recommendation of measurement to the nearest 0.1 mm was not followed. Terminal digit clustering was marked, with consequences for T category. Pathologists, clinicians, and epidemiologists should know that clustering of thickness data around T category cut points can impact melanoma staging with consequent effect on patient management and prognosis.

中文翻译：

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黑色素瘤分期：在基于人群的研究中，Breslow厚度数据的精度和末端数字聚类变化明显

背景

Breslow厚度报告中的错误会导致T类别的错误分类，T类别是黑色素瘤分期的重要分类。

客观的

我们试图研究Breslow厚度的精度（数位）和末端数字聚类以及对T类的潜在影响。

方法

纳入了2008年至2015年间挪威所有首例经形态学证实的浸润性黑色素瘤。拟合了一个平滑模型以估计基本的Breslow厚度分布而没有数字聚类。

结果

据报告有13,057名患者（97.5％）的厚度；中位数为1.0毫米（范围为0.09-85）。据报道为整数（15.6％），小数点后一位（78.2％）和小数点后两位（6.2％）-薄型肿瘤比厚型肿瘤更精确。发现终端数字聚类在终端数字0和5的观察到的频率分布中具有明显的峰值，并在这些峰值附近出现下降。末位数字聚类增加了被分类为T1和T4肿瘤的患者比例，并降低了被分类为T2和T3的比例。

局限性

在2.5％的病例中未报告Breslow厚度。

结论

没有遵循挪威建议的精确到0.1毫米的测量建议。标出了末尾数字聚类，对T类产生了影响。病理学家，临床医生和流行病学家应该知道，围绕T类切点的厚度数据聚类会影响黑色素瘤的分期，从而对患者的治疗和预后产生影响。