细胞核是真核细胞特有的细胞结构，是真核细胞重要的组成部分，是一种封闭式膜状细胞器。细胞核是细胞代谢、细胞遗传的调控中心。细胞核内部含有细胞中绝大多数的遗传物质，就是DNA。这些DNA与多种蛋白质（组织蛋白和非组织蛋白）、少量的mRNA等复合形成染色质，而染色质在细胞分裂时，会被压缩，形成染色体，其中所含的所有基因合称为核基因组。细胞核的作用，是维持基因的完整性，并借由调节基因表现来影响细胞活动。

Folded and invaginated nuclei (E) are seen in the endothelial cells of this collapsed blood vessel from the subsynovial tissue of man. X 14000 

在这张来自人体滑膜组织的血管中，可以看到内皮细胞中折叠和内陷的细胞核（E）。放大倍数为14000倍。

Support for this hypothesis may also be found in the case of tumours where complex nuclear form is associated with a high metabolic activity. The marked irregularities of shape assumed by neoplastic nuclei are well known to the light microscopist and this feature is of some value in the diagnosis of malignant tumours. The electron microscope reveals even more dramatically the extremes of complex and bizarre forms the nuclei of tumour cells can assume {Plate 2, Fig. 1). At times the nucleus is so extensively segmented or invaded by numerous invaginations (Plate 2, Fig. 2) that it assumes a sponge-like characte.

复杂的核形态与高代谢活动相关。肿瘤细胞核形态的显著不规则特征为光学显微镜观察者所熟知，并且这一特征在恶性肿瘤的诊断中具有一定的价值。电子显微镜更加明显地显示了肿瘤细胞核可以呈现出复杂和奇异形态的极端情况（图板2，图1）。有时，细胞核会被多个内陷（图板2，图2）广泛分割或侵入，以至于呈现出海绵状的特征。

Fig. 1. Cell from a well differentiated osteogenic sarcoma showing two irregular nuclear profiles with small pedunculated masses of nuclear substance connected by complex slender stalks. X 7000 (From Ghadially and Mehta, 1970)

Fig. 2. A nucleus from a metastatic malignant melanoma. Invaginations of the nuclear envelope (arrows) have produced numerous pseudoinclusions (P) which give the nucleus a sieve-like or sponge-like appearance. X 15 000

图1：来自良性分化的成骨肉瘤的细胞，显示出两个不规则的核轮廓，核物质的小柄状团块通过复杂的细长柄相连。放大倍数为7000倍。（引自Ghadially和Mehta，1970）

图2：转移性恶性黑色素瘤的细胞核。核膜的内陷（箭头）形成了大量的伪包涵体（P），使细胞核呈现出筛子状或海绵状的外观。放大倍数为15000倍。