Carcinoma in situ
Encyclopedia
Carcinoma in situ is an early form of cancer
that is defined by the absence of invasion of tumor cells into the surrounding tissue, usually before penetration through the basement membrane
. In other words, the 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, that has failed to penetrate into the deeper dermis.
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, do form tumors, such as in the colon (polyps), in the bladder (pre-invasive papillary cancer), or in the breast (more properly called ductal carcinoma in situ).
Many forms of invasive carcinoma
(the most common form of cancer
) originate after progression of 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 laboratory report
to a patient, most doctors will refer to CIS as "pre-cancer", not cancer. However, because most forms of CIS have a high probability of progression into invasive carcinoma, doctors will usually recommend that the lesion be completely removed. Therefore, CIS is usually treated in much the same way as a malignant tumor.
In the TNM classification, carcinoma in situ is reported as TisN0M0 (Stage
0).
unless it progresses into a "true" cancer. Therefore, its removal eliminates the risk of subsequent progression into a life-threatening condition. This concept is in some ways analagous to uprooting a tree - easy when a young sapling, and much more difficult later.
Some forms of CIS (e.g. colon polyps
and polypoid tumours of the bladder
) can be removed using an endoscope, without conventional surgical resection
. 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 require major surgery, the best known being intraductal carcinoma of the breast (also treated with radiotherapy). One of the most dangerous forms of CIS is the "pneumonic form" of bronchioloalveolar carcinoma
of the lung, which can require extensive surgical removal of large parts of the lung. When too large, it often cannot be completely removed, with eventual disease progression and death of the host.
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
that is defined by the absence of invasion of tumor cells into the surrounding tissue, usually before penetration through the basement membrane
Basement membrane
The basement membrane is a thin sheet of fibers that underlies the epithelium, which lines the cavities and surfaces of organs including skin, or the endothelium, which lines the interior surface of blood vessels.- Composition :...
. In other words, the 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
Bowen's disease
Bowen's disease is a neoplastic skin disease, it can be considered as an early stage or intraepidermal form of squamous cell carcinoma. It was named after Mark Bowen...
, is the accumulation of neoplastic epidermal cells within the epidermis only, that has failed to penetrate into the deeper dermis.
For this reason, CIS will usually not form a tumor
Tumor
A tumor or tumour is commonly used as a synonym for a neoplasm that appears enlarged in size. Tumor is not synonymous with cancer...
. 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, do form tumors, such as in the colon (polyps), in the bladder (pre-invasive papillary cancer), or in the breast (more properly called ductal carcinoma in situ).
Many forms of invasive carcinoma
Carcinoma
Carcinoma is the medical term for the most common type of cancer occurring in humans. Put simply, a carcinoma is a cancer that begins in a tissue that lines the inner or outer surfaces of the body, and that generally arises from cells originating in the endodermal or ectodermal germ layer during...
(the most common form of cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
) originate after progression of 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
Malignant
Malignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...
neoplasm.
When explaining a laboratory report
Pathology
Pathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
to a patient, most doctors will refer to CIS as "pre-cancer", not cancer. However, because most forms of CIS have a high probability of progression into invasive carcinoma, doctors will usually recommend that the lesion be completely removed. Therefore, CIS is usually treated in much the same way as a malignant tumor.
In the TNM classification, carcinoma in situ is reported as TisN0M0 (Stage
Cancer staging
The stage of a cancer is a description of the extent the cancer has spread. The stage often takes into account the size of a tumor, how deeply it has penetrated, whether it has invaded adjacent organs, how many lymph nodes it has metastasized to , and whether it has spread to distant organs...
0).
Dysplasia vs carcinoma in situ vs invasive carcinoma
These terms are related since they represent the three steps of the progression toward cancer:- DysplasiaDysplasiaDysplasia , is a term used in pathology to refer to an abnormality of development. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells. Dysplasia is often indicative of an early neoplastic process...
is the earliest form of pre-cancerous lesion recognizable in a biopsyBiopsyA biopsy is a medical test involving sampling of cells or tissues for examination. It is the medical removal of tissue from a living subject to determine the presence or extent of a disease. The tissue is generally examined under a microscope by a pathologist, and can also be analyzed chemically...
by a pathologistPathologyPathology is the precise study and diagnosis of disease. The word pathology is from Ancient Greek , pathos, "feeling, suffering"; and , -logia, "the study of". Pathologization, to pathologize, refers to the process of defining a condition or behavior as pathological, e.g. pathological gambling....
. 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 cancerCancerCancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
, is the final step in this sequence. It is a disease that, if left untreated, will invade and spread to surrounding tissues and structures of the host (hence its name), and may eventually be lethal.
Examples
- Many bladder cancerBladder cancerBladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
s are CIS. - Cervical cancerCervical cancerCervical cancer is malignant neoplasm of the cervix uteri or cervical area. One of the most common symptoms is abnormal vaginal bleeding, but in some cases there may be no obvious symptoms until the cancer is in its advanced stages...
is often predated by cervical squamous intraepithelial lesionCervical intraepithelial neoplasiaCervical intraepithelial neoplasia , also known as cervical dysplasia and cervical interstitial neoplasia, is the potentially premalignant transformation and abnormal growth of squamous cells on the surface of the cervix. CIN is not cancer, and is usually curable...
(SIL, previously CIN, a form of dysplasiaDysplasiaDysplasia , is a term used in pathology to refer to an abnormality of development. This generally consists of an expansion of immature cells, with a corresponding decrease in the number and location of mature cells. Dysplasia is often indicative of an early neoplastic process...
). 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 smearPap smearThe Papanicolaou test is a screening test used in to detect pre-cancerous and cancerous processes in the endocervical canal of the female reproductive system. Changes can be treated, thus preventing cervical cancer...
. - Ductal carcinoma in situ (DCIS) of the breast is a rather frequent disease with a high probability of transforming into true breast cancerBreast cancerBreast cancer is cancer originating from breast tissue, most commonly from the inner lining of milk ducts or the lobules that supply the ducts with milk. Cancers originating from ducts are known as ductal carcinomas; those originating from lobules are known as lobular carcinomas...
if left untreated. - Bowen's diseaseBowen's diseaseBowen's disease is a neoplastic skin disease, it can be considered as an early stage or intraepidermal form of squamous cell carcinoma. It was named after Mark Bowen...
is squamous carcinoma in situ of the skin. - Colon polypsPolyp (medicine)A polyp is an abnormal growth of tissue projecting from a mucous membrane. If it is attached to the surface by a narrow elongated stalk, it is said to be pedunculated. If no stalk is present, it is said to be sessile. Polyps are commonly found in the colon, stomach, nose, sinus, urinary bladder...
often contain areas of CIS that will almost always transform into colon cancer if left untreated. - High grade prostatic intraepithelial neoplasia is equivalent to CIS of the prostate.
- Bronchioloalveolar carcinomaBronchioloalveolar carcinomaBronchioloalveolar carcinoma is a term describing certain variants of lung cancer arising in the distal bronchioles or alveoli that initially exhibit a specific non-invasive growth pattern.-Classification:...
(BAC) of the lung is the only form of CIS that can kill directly because, in rare cases (the "pneumonic form"), it expands greatly and fills the lungs, preventing breathing and causing other dire effects on the host. Thus, the pneumonic form of BAC is a true malignantMalignantMalignancy is the tendency of a medical condition, especially tumors, to become progressively worse and to potentially result in death. Malignancy in cancers is characterized by anaplasia, invasiveness, and metastasis...
entity, but is not "invasive" in the classical sense. For this reason, it is considered a form of CIS by pathologists, but not by oncologists or surgeons and inclusion of this form of cancer among the types of CIS is controversial.
Treatment
Carcinoma in situ is, by definition, a localized phenomenon, with no potential for metastasisMetastasis
Metastasis, or metastatic disease , is the spread of a disease from one organ or part to another non-adjacent organ or part. It was previously thought that only malignant tumor cells and infections have the capacity to metastasize; however, this is being reconsidered due to new research...
unless it progresses into a "true" cancer. Therefore, its removal eliminates the risk of subsequent progression into a life-threatening condition. This concept is in some ways analagous to uprooting a tree - easy when a young sapling, and much more difficult later.
Some forms of CIS (e.g. colon polyps
Adenoma
An adenoma is a benign tumor of glandular origin. Adenomas can grow from many organs including the colon, adrenal glands, pituitary gland, thyroid, prostate, etc. Although these growths are benign, over time they may progress to become malignant, at which point they are called adenocarcinomas...
and polypoid tumours of the bladder
Bladder cancer
Bladder cancer is any of several types of malignant growths of the urinary bladder. It is a disease in which abnormal cells multiply without control in the bladder. The bladder is a hollow, muscular organ that stores urine; it is located in the pelvis...
) can be removed using an endoscope, without conventional surgical resection
Resection
Resection may refer to:*Segmental resection , the partial removal of an organ or other body structure*Resection , a means of establishing a location...
. Dysplasia of the uterine cervix
Cervical intraepithelial neoplasia
Cervical intraepithelial neoplasia , also known as cervical dysplasia and cervical interstitial neoplasia, is the potentially premalignant transformation and abnormal growth of squamous cells on the surface of the cervix. CIN is not cancer, and is usually curable...
is removed by excision (cutting it out) or by burning with a laser. Bowen's disease
Bowen's disease
Bowen's disease is a neoplastic skin disease, it can be considered as an early stage or intraepidermal form of squamous cell carcinoma. It was named after Mark Bowen...
of the skin is removed by excision. Other forms require major surgery, the best known being intraductal carcinoma of the breast (also treated with radiotherapy). One of the most dangerous forms of CIS is the "pneumonic form" of bronchioloalveolar carcinoma
Bronchioloalveolar carcinoma
Bronchioloalveolar carcinoma is a term describing certain variants of lung cancer arising in the distal bronchioles or alveoli that initially exhibit a specific non-invasive growth pattern.-Classification:...
of the lung, which can require extensive surgical removal of large parts of the lung. When too large, it often cannot be completely removed, with eventual disease progression and death of the host.