S

S-phase fraction: Percentage of cells replicating their DNA. Replication usually means a cell is getting ready to split into two new cells. A low s-phase fraction indicates a slow cell division and a slow-growing tumor; a high s-phase fraction indicates cells are dividing rapidly and the tumor is growing quickly.

Sarcoma: Malignant tumor growing from connective tissues, such as cartilage, fat, muscle, or bone.  Found in many parts of the body, including the cervix.

Scan: Study using x-rays or radioactive isotopes to produce images of internal organs.

Scintillation camera: Instrument used in nuclear medicine scans to detect radioactivity and produce images that help diagnose cancer and other diseases.

Screen: A search for disease, such as cancer, in people without symptoms. A screening for prostate cancer, for instance, include digital rectal examination and the PSA blood test; for breast cancer, mammographies and clinical breast exams. Screening also may refer to coordinated programs in large populations.

Secondary tumor: Tumor formed as a result of spread (metastasis) of cancer from the place where it started.

Sentinel lymph node biopsy: Relatively new procedure that may replace standard axillary lymph node dissection. The procedure involved injection of a dye or a radioisotope tracer into the tumor site at time of surgery. The first (called the "sentinel") node that picks up the dye is removed and biopsied. If the node is cancer- free, no more nodes are removed.

Sequence: See base sequence.

Sequence tagged site (STS): Short (200 to 500 base pairs) DNA sequence that has a single occurrence in the human genome and whose location and base sequence are known. Detectable by polymerase chain reaction, STSs are useful for localizing and orienting the mapping and sequence data reported from many different laboratories and serve as landmarks on the developing physical map of the human genome. Expressed sequence tags (ESTs) are STSs derived from cDNAs.

Sequencing: Determination of the order of nucleotides (base sequences) in a DNA or RNA molecule or the order of amino acids in a protein.

Sex chromosome:The X or Y chromosome in human beings that determines the sex of an individual. Females have two X chromosomes in diploid cells; males have an X and a Y chromosome. The sex chromosomes comprise the 23rd chromosome pair in a karyotype. Compare autosome.

Sexual therapist: Specially trained mental health professional who counsels people about sexual changes, problems, and communication.

Shotgun method: Sequencing method which involves randomly sequencing tiny cloned pieces of the genome, with no foreknowledge of where on a chromosome the piece originally came from. This can be contrasted with "directed" strategies, in which pieces of DNA from adjacent stretches of a chromosome are sequenced. Directed strategies eliminate the need for complex reassembly techniques. Because there are advantages to both strategies, researchers expect to use both random (or shotgun) and directed strategies in combination to sequence the human genome. See library, genomic library.
Side effects: Negative after-effects of treatment such as hair loss caused by chemotherapy, or nausea and fatigue caused by radiation or chemotherapy.

Sigmoidoscope: Flexible, hollow, slender lighted tube of about half inch diameter that is inserted through the rectum. Often a gas is injected into the colon to expand it further. This enables a doctor to look at the inside of the rectum and part of the colon for cancer and polyps. Some sigmoidoscopes are connected to a video camera and video display monitor so the doctor can look closely at the inside of the colon. (Polyps are small growths that can become cancerous.) The test may be somewhat uncomfortable, but it should not be painful.

Sigmoidoscopy: Test to help find cancer or polyps on the inside of the rectum and part of the colon.

Simple mastectomy or total mastectomy: Removal only of the breast and areola.

Single-gene disorder: Hereditary disorder caused by a mutant allele of a single gene (e.g., Duchenne muscular dystrophy, retinoblastoma, sickle cell disease). Compare polygenic disorder.

Social worker: Health professional who aids people in their search to find community resources and support services. Also provides counseling and guidance to assist with wide range of concerns such as insurance coverage, nursing home placement, etc..

Somatic cell: Any cell in the body except gametes and their precursors.

Southern blotting: Transfer by absorption of DNA fragments separated in electrophoretic gels to membrane filters for detection of specific base sequences by radiolabeled complementary probes.

Speech therapist: Specially trained person who works with people who have lost the ability to speak clearly. Speech therapists help re-establish communication skills and also assure that patients learn to easily eat and drink again after treatment.

Spinal tap: Procedure in which a needle is inserted into the spinal canal to withdraw a small amount of spinal fluid or to provide medicine directly to the central nervous system through the spinal fluid.

Sputum cytology: Microscopic study of phlegm cells to determine if they are normal or not.

Squamous cell carcinoma: Cancer beginning in non-glandular cells. Skin cancer, for example.

Staging : Process of determining if cancer has spread and if so, how far. There are several staging systems. The TNM system is one of the most common. The TNM system provides three important pieces of information:
-- "T" - the size of a TUMOR 
-- "N" - how far cancer has spread to nearby NODES 
-- "M" - whether cancer has spread (METASTACIZED) to other organs
-- Letters or numbers after the T, N, and M provide more details about each factor. The TNM descriptions also can be grouped together into a simple set of stages, labeled with Roman numerals. Generally, the lower the number, the less the cancer has spread. Higher numbers mean a more serious cancer.

Stem cell and stem cell transplant: Immature blood cells (called stem cells) are taken from the patient's blood and later, in the lab, stimulated with growth factors to produce more stem cells which are then returned to the patient by transfusion.

STD: Sexually transmitted disease, such as chlamydia, syphilis, AIDS, etc.

Stenosis: Narrowing (stricture) of a duct or canal.

Stereotactic needle biopsy: Method of needle biopsy useful in some cases where calcifications or a mass can be seen on mammogram but cannot be found by touch. A computer maps the location of the mass to guide the needle to the site where it then gathers the desired sample. (See: Aspiration, Needle biopsy.)

Stereotactic radiosurgery: New treatment focusing high doses of radiation on a tumor while limiting exposure of normal tissue. Useful for treating tumors in places where regular surgery would harm essential tissue, for example, in the brain or spinal cord. Also may be used when a patient's condition does not permit regular surgery.

Stoma: Opening, especially one made surgically to allow elimination of body waste. (See: Colostomy, Ileostomy, Urostomy.)

Stomatitis: Mouth area ulcers or inflammation. Also can be side effect of some types of chemotherapy.

STS: See sequence tagged site.

Subcutaneous mastectomy: Removal of the internal breast tissue. The nipple and skin are left intact.

Supraclavicular lymph: Lymph nodes found just above collarbone (clavicle).

Surgeon: Doctor who performs operations.

Surgical biopsy: (See: Biopsy.)

Surgical oncologist: Doctor specializing in use of surgery to treat cancer.

Survival rate: Percentage of survivors with no trace of disease within a specified period after diagnosis or treatment. For cancer, five-year survival rates are frequently provided. This does not mean people cannot live more than five years or that those who survive five years are necessarily permanently cured.

Synchronous: At the same time. Cancer in both ovaries at the same time, for instance, is said to be synchronous.

Synergistic: Acting or working together - often to produce an effect greater than the sum of each could produce acting alone. 

Systemic disease: System-wide. When used in reference to cancer, this term means a tumor that originated in one place has spread to other distant organs or structures.

Systemic therapy: Treatment reaching and affecting cells throughout the body. Chemotherapy, for instance, is a systemic therapy.