Carcinoma in situ
1125428
217127282
2008-06-04T18:47:04Z
Juliancolton
2793164
Reverted edits by [[Special:Contributions/67.160.191.65|67.160.191.65]] ([[User talk:67.160.191.65|talk]]) to last version by Haymanj
'''Carcinoma in situ''' (CIS) is an early form of [[carcinoma]] defined by the absence of invasion of surrounding tissues. In other words, the [[neoplasm|'''neoplastic cells''']] proliferate in their normal habitat, hence the name 'in situ' (Latin for 'in its place'). For example, carcinoma in situ of the skin, also called [[Bowen's disease]] is the accumulation of neoplastic epidermal cells within the epidermis only.
For this reason, CIS will usually not form a '''[[tumor]]'''. Rather, the lesion is flat (in the skin, cervix, etc) or follows the existing architecture of the organ (in the breast, lung, etc). Some CIS, however, form tumors, for example colon polyps or papillary cancer of the bladder.
Many forms of '''invasive [[carcinoma]]''' (the most common form of [[cancer]]) originate from a CIS lesion. Therefore, CIS is considered a '''precursor''' or '''incipient''' form of cancer that may, if left untreated long enough, transform into a [[malignant]] [[neoplasm]].
When explaining a [[pathology|laboratory report]] to a patient, most doctors will refer to CIS as '''pre-cancer''', not cancer. However, because most forms of CIS have a real potential to turn into invasive carcinoma, doctors will usually recommend that the lesion be completely removed. Therefore, CIS is usually treated much the same way as a malignant tumor.
In the [[TNM]] classification, carcinoma in situ is indicated as TisN0M0 ([[Cancer staging|Stage]] 0).
==Dysplasia vs ''carcinoma in situ'' vs invasive carcinoma==
These terms are related since they represent the three steps of the progression toward cancer:
*'''[[Dysplasia]]''' (from the Greek δυσπλασία "malformation", δυσ- "mal-" + πλάθω "to create, to form"), is the earliest form of pre-cancerous lesion recognizable in a [[biopsy]] by a [[pathology|pathologist]]. Dysplasia can be '''low grade''' or '''high grade''' (see CIS below). The risk of low-grade dysplasia transforming into cancer is low.
*'''Carcinoma in situ''' is synonymous with '''high-grade dysplasia''' in most organs. The risk of transforming into cancer is high.
*'''Invasive carcinoma''', commonly called '''[[cancer]]''', is the final step in this sequence. It is a disease that, when left untreated, will invade the host (hence its name) and may be lethal.
==Examples of ''carcinomata in situ''==
* Many [[bladder cancer]]s are CIS.
* [[Cervical cancer]] is often predated by cervical [[Cervical intraepithelial neoplasia|''squamous intraepithelial lesion'']] (SIL, previously CIN, a form of [[dysplasia]]). The term CIS is not used for the cervix. Instead, the term ''high grade SIL'' (HSIL) is used, essentially a synonym. It is this lesion that is detected with the [[pap smear]].
* [[Ductal carcinoma in situ]] (DCIS) of the breast is a rather frequent disease with a high probability of transforming into true [[breast cancer]] if untreated.
* [[Bowen's disease]] is [[squamous carcinoma]] in situ of the skin.
* [[Polyp (medicine)|Colon polyps]] often contain areas of CIS that will almost always turn into [[colon cancer]] if left untreated.
* High grade [[Prostatic intraepithelial neoplasia]] is equivalent to CIS of the prostate.
* [[Bronchioloalveolar carcinoma]] of the lung is the only form of CIS that can kill because it fills the lungs and prevents breathing. Thus, it is [[malignant]], but not invasive. For this reason, this unusual form of carcinoma is seen as CIS by [[pathologists]], not by [[oncologists]] or [[surgeons]]. Therefore, its inclusion among the CIS category is controversial.
[[Image:Ca in situ, cervix 2.jpg|thumb|High grade dysplasia (carcinoma in situ) in the uterine cervix. The abnormal epithelium is extending into a mucus gland to the left of centre. This disease can progress to invasive cancer (squamous cell carcinoma) of the cervix.]]
== Treatment ==
Carcinoma in situ is, by definition, localized, with no potential for [[metastasis]] unless it progresses into a true cancer. Therefore, its removal eliminates the risk of cancer. It can be compared to uprooting a tree, easy when a young sapling, more difficult later.
Some forms (e.g. [[Adenoma|colon polyps]] and polypoid [[Bladder cancer|tumors of the bladder]]) can be removed using an [[endoscope]], without true surgery. [[Cervical intraepithelial neoplasia|Dysplasia of the uterine cervix]] is removed by excision (cutting it out) or by burning with a laser. [[Bowen's disease]] of the skin is removed by excision. Other forms of CIS require major surgery, the best known being [[Ductal carcinoma|Intraductal carcinoma of the Breast]]. The most difficult form of CIS is [[Bronchioloalveolar carcinoma]] of the Lung, which requires the removal of large parts of the lung. When too large, it cannot be removed and often kills its host.
[[ductal carcinoma|Intraductal carcinoma of the Breast]] is also treated with [[radiotherapy]].
==See also==
* [[Cancer]]
* [[Neoplasia]]
* [[Dysplasia]]
* [[Carcinoma]]
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[[Category:Histopathology]]
[[Category:Types of cancer]]
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