D

D & C: Dilatation and curettage. Test in which the cervix is opened slightly so that a sample of tissue from the lining of the uterus can be removed and studied.Deletion Map: A description of a specific chromosome that uses defined mutations -specific deleted areas in the genome- as "biochemical signposts," or markers for specific areas.

Deoxyribonucleotide: See nucleotide.

Dermatologist : Doctor specializing in skin diseases.

DES : (See: Diethylstilbestrol.)

Diagnosis : Identification of a disease by its signs or symptoms.

Diethylstilbestrol die-eth-l-steh-BES-ter-ol : Synthetic form of estrogen.

Dietitian/registered dietitian/nutritionist : An expert in food and diet; a registered dietitian (RD) has at least a bachelor's degree and has passed a national competency exam. The term nutritionist is also used, but there are no educational requirements associated with this title.

Differentiation : Normal process through which cells mature so they can carry out the jobs they were meant to do. Cancer cells are less differentiated than normal cells. Grading is done to evaluate and report the degree of a cancer's differentiation.

Digital mammography : Method of storing X-ray images of the breast as computer images rather than on film. Digital mammography can be combined with computer-assisted diagnosis (CAD), a process in which the radiologist uses a computer to interpret mammograms.

Digital rectal exam (DRE): Doctor inserts gloved finger into the rectum to feel for anything not normal. Some tumors of the rectum and prostate gland can be detected during a DRE.

Diploid: A full set of genetic material, consisting of paired chromosomes one chromosome from each parental set. Most animal cells except the gametes have a diploid set of chromosomes. The diploid human genome has 46 chromosomes. Compare haploid.

Dissection : Surgical division, separation, or removal of tissues. (See: Axillary dissection.)

DNA : (See: Deoxyribonucleic acid.)

DNA repair : Correcting genetic mistakes that are made each time a cell divides. If the repair process does not go right, however, it can increase the chances of a person having some forms of cancer.

DNA (deoxyribonucleic acid): The molecule that encodes genetic information. DNA is a doublestranded molecule held together by weak bonds between base pairs of nucleotides. The four nucleotides in DNA contain the bases: adenine (A), guanine (G), cytosine (C), and thymine (T). In nature, base pairs form only between A and T and between G and C; thus the base sequence of each single strand can be deduced from that of its partner.

DNA probe: See probe.

DNA replication: The use of existing DNA as a template for the synthesis of new DNA strands. In humans and other eukaryotes, replication occurs in the cell nucleus.

DNA sequence: The relative order of base pairs, whether in a fragment of DNA, a gene, a chromosome, or an entire genome. See base sequence analysis.

Domain: A discrete portion of a protein with its own function. The combination of domains in a single protein determines its overall function.

Dosimetrist do-sim-uh-trist : Person who plans and calculates the proper radiation dose for cancer treatment.

Double contrast barium enema (DCBE), also called barium enema with air contrast: A colorectal cancer diagnostic test that uses barium sulfate, a chalky substance, to partially fill and open the colon. When the colon is about half-full of barium, air is inserted to cause the colon to expand. This allows x-ray films to show abnormalities of the colon.

Double helix: The shape that two linear strands of DNA assume when bonded together.

Doubling time : Time it takes for a cell to divide. Cancers vary in doubling time from 8 to 600 days, averaging 100 to 120 days. Therefore cancer may be present for many years before being detected.

DRE : (See: Digital rectal exam.)

Drug resistance : Ability of cancer cells to become resistant to the effects of the chemotherapy drugs used to treat cancer.

Duct ectasia : Widening of the ducts of the breast, often related to breast inflammation called periductal mastitis.

Duct ectasia is a benign (not cancerous) condition. Symptoms include a nipple discharge, swelling, retraction of the nipple, or a lump that can be felt.

Ductal carcinoma in situ ( DCIS) : Cancer cells that start in the milk passages (ducts) of the breast but have not penetrated the duct walls into surrounding tissue. This highly curable form of breast cancer is treated with surgery, or surgery plus radiation therapy. (Also called intraductal carcinoma.)

Dysphagia dis-fay-je-uh : Trouble swallowing or eating.

Dysplasia dis-play-zuh : Abnormal tissue development.