Sub-populations of melanocytes in pigmented basal cell carcinoma

色素沉着是日本基底细胞癌患者的典型临床特征。色素基底细胞癌中黑色素的发病机制尚不清楚。我们结合了形态学分析和电子显微镜技术，准确地评估了发生在色素基底细胞癌的色素区和非色素区黑色素细胞的形态学方面。在色素区，黑素细胞不仅沿基底膜分布，而且散布在肿瘤巢中心部位的肿瘤细胞之间，树突大而多。在非色素区，黑素细胞仅位于基部，树突较少，经常出现流产的黑素体；而这两个部位的黑色素细胞均处于黑色素生成和增殖的活跃状态。超微结构细胞形态分析也显示，两种黑素细胞在核和细胞面积、核/细胞面积比、细胞周长和细胞形态因子等大部分核和细胞参数上存在显著差异。特别是黑色素细胞在色素区域的细胞大小是后者的两倍。此外，黑素体几乎完全保留在凋亡的肿瘤细胞中，并且含有黑素体的凋亡细胞被邻近的肿瘤细胞吞噬后，似乎会形成黑素体复合物。这些发现表明，在色素基底细胞癌中可能存在不同的黑素细胞群，并且含有黑素小体的凋亡细胞的反复吞噬循环可能是形成大型黑素小体复合物的主要方式。本文的形态学观察和定量分析为进一步研究解释色素基底细胞癌的其他病理变化提供了形态学基础。

Pigmentation is a characteristic clinical feature of basal cell carcinomas in Japanese patients. The pathogenesis of melanin pigment in pigmented basal cell carcinomas is poorly understood. We have combined the techniques of morphometric analysis and electron microscopy to assess accurately the morphologic aspects of melanocytes that occurred in pigmented and non-pigmented areas of pigmented basal cell carcinomas.n the pigmented areas melanocytes were not only located along the basal membrane but also interspersed between tumor cells in the central parts of the tumor nest, and had large and numerous dendrites. In the non-pigmented areas melanocytes were only basally located, showed fewer dendrites, and frequently showed abortive melanosomes ; However, melanocytes in these two different portions were in the active state of melanogenesis and proliferation.Ultrastructural cytomorphometric analysis also showed significant differences in most of the nuclear and cell parameters including nuclear and cell area, the nuclear/cell area ratio, cell perimete and cell form factor between these two types of melanocytes. Particularly melanocytes in the pigmented areas were twice the cell size of the latter. In addition, the melanosomes remained almost completely in the apoptotic tumor cells, and the phagocytosis of the melanosome-containing apoptot cells by the neighboring tumor cells appeared to be followed by the formation of the melanosome complexes.These findings suggest that different populations of melanocytes are probably present in pigmented basal cell carcinomas, and repeated cycles of phagocytosis of melanosome-containing apoptotic cells may represent the predominant way of forming large melanosome complexes. The present morphological observation and quantitative analysis provide a morphological basis for furthe studies to interpret other pathologic changes in pigmented basal cell carcinomas.