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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.



The large fronds of endometrium seen in this uterus opened to reveal the endometrial cavity are a result of hyperplasia. This resulted from increased estrogen. With hyperplasia, there is an increase in cell numbers to produce an increase in tissue size. However, the cells are normal in appearance. Sometimes hyperplasias can be "atypical" and the cells not completely normal. Such conditions can be premalignant.



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。

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.


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....


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.


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.


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.


This is a neoplasm. Neoplasia is uncontrolled new growth. Note the mass of abnormal tissue on the surface of the cervix. The term "tumor" is often used synonymously with neoplasm, but a "tumor" can mean any mass effect, whether it is inflammatory, hemodynamic, or neoplastic in origin. Once a neoplasm has started, it is not reversible.


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