Any increase in tissue size is not necessarily neoplasia. Here is an example of left ventricular cardiac hypertrophy in which there has been an increase in the size of the myocardial fibers in response to an increased pressure load from hypertension. With hypertrophy, the cells increase in size, but the cells do not increase in number. Except for being larger, the cells are normal in appearance.

图示：左心室肥大

并不是所有的组织体积增大的病变都属于肿瘤。为了适应高血压时过重的压力负荷左心室发生了这种变化。心肌纤维数量没有增加，体积增大了，但结构正常。

The first step toward neoplasia（肿瘤形成） is cellular transformation（变化、转化、转换）. Here, there is metaplasia （化生）of normal respiratory（呼吸的） laryngeal（喉的） epithelium on the right to squamous（鳞状的） epithelium on the left in response to chronic irritation of smoking. The two forms of cellular transformation that are potentially reversible, but may be steps toward a neoplasm, are:

• Metaplasia(化生): the exchange of normal epithelium for another type of epithelium. Metaplasia is reversible when the stimulus for it is taken away.
• Dysplasia（非典型增生）: a disordered growth and maturation of an epithelium, which is still reversible if the factors driving it are eliminated.

肿瘤形成首先是细胞发生变化，图示是右侧正常喉部呼吸上皮向鳞状上皮化生，左侧化生是由于慢性抽烟损伤。 这两类细胞变化潜在可逆，也可能向肿瘤发展。
化生：正常上皮转变成另一类上皮细胞。当刺激撤消后，化生可逆
非典型增生：上皮的异常增生和分化，如果刺激因子去除后，仍然可逆。

This biopsy（活检） of the lower esophagus（食管） in a patient with chronic gastroesophageal（胃食管的） reflux （逆流）disease shows columnar（柱状的）metaplasia （化生）(Barrett's esophagus), and the goblet cells（杯状细胞） are typical of an intestinal（肠的） type of epithelium. Squamous（鳞状的） epithelium typical of the normal esophagus （食管）appears at the right.

图示是慢性胃食管返流征病人Barrett食管柱状上皮化生的下段食管活检结果。杯状细胞是肠上皮的典型细胞，右侧是正常食管的鳞状上皮细胞。

The best way to make the diagnosis of Pneumocystis carinii（卡氏肺孢子虫） pneumonia（肺炎） is to perform a Gomori（戈莫里法—染磷酸酶及脂酶） methenamine（乌洛托品）silver（环六亚甲基四胺银）(GMS) stain on the lung tissue or bronchoalveolar（支气管肺泡的） lavage（灌洗）(BAL) fluid（液体）. The cyst （包囊）wall is stained, and the organisms（生物体） appear as crushed （变形的）ping-pong balls, or crescent（新月形的） shapes, or folded spheres（球）, or flattened （变平的）beach（海滩） balls, or deflated（放气的） tennis
balls, or....

诊断卡氏肺孢子虫肺炎最好的方法是肺组织或支气管肺泡灌洗液进行GMS染色。染色后虫体壁着色，虫体表现为变形的乒乓球样、新月形、压迫的球形等不规则形状。

This is the next step toward neoplasia. Here, there is normal cervical（子宫颈的） squamous epithelium at the left, but dysplastic（非典型增生） squamous epithelium at the right. Dysplasia is a disorderly growth of epithelium, but still confined to the epithelium. Dysplasia is still reversible.

At high magnification, the normal cervical squamous epithelium at the left merges into the dysplastic（非典型增生） squamous epithelium at the right in which the cells are more disorderly.

高倍镜图示：左侧为正常子宫颈鳞状上皮，右侧为非典型增生的鳞状上皮，表现为细胞排列紊乱。

Some epithelia are accessible enough, such as the cervix, that cancer screening can be done by sampling some of the cells and sending them to the laboratory. Here is a cervical Pap smear in which dysplastic cells are present that have much larger and darker nuclei than the normal squamous cells with small nuclei and large amounts of cytoplasm.

一些部位象子宫颈上皮很容易发生恶变，肿瘤筛选常常选宫颈上皮细胞进行实验室检查。图示是巴氏涂片后非典型增生的宫颈细胞的表现，细胞体积增大，胞核浓染，核体积缩小，细胞浆增多。

When the entire epithelium is dysplastic and no normal epithelial cells are left, then the process is beyond dysplasia and is now neoplasia. If the basement membrane is still intact, as shown here, then the process is called "carcinoma in situ" because the carcinoma is still confined to the epithelium.

当上皮全层发生非典型增生时，就已经形成肿瘤了。如图所示：当基底膜完整时，我们称“原位癌”，因为肿瘤还局限在上皮内。