Litzner Brandon R, Etufugh Chukwuemeka N, Stepenaskie Shelly, Hynan Linda S, Cockerell Clay J
Department of Dermatology, University of Texas-Southwestern Medical Center, Dallas, TX 75390-9069, USA.
Am J Dermatopathol. 2012 Dec;34(8):827-32. doi: 10.1097/DAD.0b013e3182604d96.
The mitotic rate (MR) of malignant melanoma (MM) refers to the number of mitoses per square millimeter. Studies have suggested that it is an independent prognostic variable predicting survival in patients with MM, and it was recently included in the American Joint Committee on Cancer (AJCC) recommendations for diagnosis and treatment of MM. The AJCC melanoma staging committee recommends using the "hot-spot" approach to determine the MR, whereby it is reported as the maximum dermal mitotic figures identified in a 1-mm area of the melanoma. The AJCC has recommended that the MR be determined in all melanomas, irrespective of Breslow depth or other features. We aimed to quantify the MR in MM ≤1 mm in thickness and to identify statistical associations between the MR, Breslow depth, and Clark level. In addition, we hoped to identify practical issues in determining the MR via the hot-spot technique. We conducted a prospective study to determine the MR, Breslow depth, and Clark level in MM ≤1 mm in thickness. Seven melanomas were identified with epidermal mitoses only (7.4%). Sixteen melanomas had dermal mitoses (16.8%); of these, the majority (75.0%) contained only one mitotic figure. Seventy-nine melanomas had no dermal mitoses (83.2%). Seven lesions (7.4%) demonstrated multiple mitoses; 4 with ≥2 dermal mitoses/mm and 3 with multiple epidermal mitoses. We conclude that thin MM with >1 mitosis/mm is rare and discuss practical and theoretical issues with determining the MR using the hot-spot approach.
恶性黑色素瘤（MM）的有丝分裂率（MR）是指每平方毫米的有丝分裂数。研究表明，它是预测MM患者生存的一个独立预后变量，最近被纳入美国癌症联合委员会（AJCC）关于MM诊断和治疗的建议中。AJCC黑色素瘤分期委员会建议采用“热点”方法来确定MR，据此将其报告为在黑色素瘤1毫米区域内识别出的最大真皮有丝分裂数。AJCC建议在所有黑色素瘤中确定MR，无论其Breslow厚度或其他特征如何。我们旨在量化厚度≤1毫米的MM中的MR，并确定MR、Breslow厚度和Clark分级之间的统计学关联。此外，我们希望确定通过热点技术确定MR时的实际问题。我们进行了一项前瞻性研究，以确定厚度≤1毫米的MM中的MR、Breslow厚度和Clark分级。仅发现7例黑色素瘤有表皮有丝分裂（7.4%）。16例黑色素瘤有真皮有丝分裂（16.8%）；其中大多数（75.0%）仅含有1个有丝分裂数。79例黑色素瘤无真皮有丝分裂（83.2%）。7个病变（7.4%）表现为多个有丝分裂；4个每毫米有≥2个真皮有丝分裂，3个有多个表皮有丝分裂。我们得出结论，每毫米有>1个有丝分裂的薄MM很少见，并讨论了使用热点方法确定MR的实际和理论问题。
