Nguyen Thuy L T, Theos Amy, Kelly David R, Busam Klaus, Andea Aleodor A
Department of Pathology, University of Alabama at Birmingham, Birmingham, AL 35294-0009, USA.
Am J Dermatopathol. 2013 Feb;35(1):e16-21. doi: 10.1097/DAD.0b013e318265fe12.
Proliferative (cellular) nodules (PN) which mimic malignant melanoma clinically and histologically are described in congenital melanocytic nevi (CMN) and may pose significant diagnostic challenges. We report the case of a 10-day-old male with a giant congenital nevus involving the neck, upper chest, back, and left shoulder containing several nodular lesions, some crusted. Biopsy of a nodule revealed densely packed nevus cells with hyperchromatic round to oval and occasionally irregularly shaped nuclei. There was no necrosis or pushing border, and the nodule blended with the adjacent nevus; however, the lesion demonstrated a significant number of mitoses (27 per mm2) and a 60% labeling index with Ki-67. Further analysis by fluorescence in situ hybridization (FISH) with a 4-color probe set targeting 6p25, 6q23, 11q13, and centromere 6 revealed increased chromosomal copy numbers of all 4 probes, which was interpreted as evidence of polyploidy. In addition, analysis of DNA copy number changes using a single nucleotide polymorphism microarray (Affymetrix, Santa Clara, CA) showed no chromosomal aberrations. The diagnosis of PN in a giant congenital nevus was eventually rendered. At 13-month follow-up, the nodules showed no evidence of growth. Our case illustrates that PNs in the neonatal period might demonstrate extreme mitotic activity. This feature is worrisome when encountered in melanocytic lesions; however, it should not trigger by itself a diagnosis of melanoma in the absence of other histologic criteria of malignancy. In addition, we document polyploidy by FISH in PN, which can potentially be misinterpreted as a FISH-positive result.
增殖性（细胞性）结节（PN）在先天性黑素细胞痣（CMN）中较为常见，在临床和组织学上可模拟恶性黑色素瘤，可能带来重大的诊断挑战。我们报告了一例10日龄男性患儿，其患有巨大先天性痣，累及颈部、上胸部、背部和左肩，包含多个结节性病变，部分有结痂。对一个结节进行活检，结果显示痣细胞密集排列，细胞核呈深染的圆形至椭圆形，偶尔形状不规则。未见坏死或推挤边缘，结节与相邻痣融合；然而，该病变显示有大量有丝分裂（每平方毫米27个），Ki-67标记指数为60%。使用针对6p25、6q23、11q13和6号染色体着丝粒的四色探针组进行荧光原位杂交（FISH）进一步分析显示，所有4个探针的染色体拷贝数均增加，这被解释为多倍体的证据。此外，使用单核苷酸多态性微阵列（Affymetrix，加利福尼亚州圣克拉拉）分析DNA拷贝数变化，未发现染色体畸变。最终诊断为巨大先天性痣中的PN。在13个月的随访中，结节未见生长迹象。我们的病例表明，新生儿期的PN可能表现出极端的有丝分裂活性。在黑素细胞病变中遇到这一特征令人担忧；然而，在没有其他恶性组织学标准的情况下，它本身不应引发黑色素瘤的诊断。此外，我们通过FISH记录了PN中的多倍体情况，这可能会被误解为FISH阳性结果。
