Glossary

Diagnosis & pathology

DCIS (ductal carcinoma in situ)

Abnormal cells confined to a milk duct (“in place”). Often called stage 0 breast cancer. Not the same as invasive breast cancer, where cells have crossed into surrounding tissue.

Stage 0

Staging label commonly used for pure DCIS (no invasive component identified on pathology). Staging can change if invasion is found later (for example at surgery).

In situ

Latin for “in place.” In DCIS, abnormal cells have not been shown to invade beyond the duct wall on the tissue examined.

Invasive breast cancer

Cancer cells have grown beyond the duct or lobule into surrounding breast tissue. Different diagnosis and usually different treatment discussions than pure DCIS.

LCIS (lobular carcinoma in situ)

A different in-situ finding in the lobules. Managed differently from DCIS; not the same diagnosis. Mentioned only so the acronym is not confused with DCIS.

Grade (nuclear grade)

How abnormal the cells look under the microscope: typically low, intermediate, or high. Higher grade is often treated as higher risk for recurrence or progression discussions.

Architecture (solid, cribriform, papillary…)

How DCIS cells are arranged in the duct. Patterns (e.g. solid, cribriform) are descriptive path terms; they help characterize the lesion along with grade and necrosis.

Comedonecrosis (necrosis)

A pattern of cell death inside the duct. Often treated as a higher-risk feature and can influence whether “watch only” paths are offered. Pathologists may disagree on borderline cases.

Calcifications

Tiny calcium deposits seen on mammogram. Many are benign; some patterns lead to biopsy and can be associated with DCIS.

Microinvasion

A very small focus of invasive cells (often ≤1 mm by definition in staging systems). Can be missed on core biopsy and discovered on surgical pathology.

Upgrade (to invasive)

When final surgery shows invasive cancer (or more extensive disease) that the core biopsy did not show. One reason teams discuss surgery for diagnosis as well as treatment.

Pathology report

The formal lab report describing tissue findings: diagnosis, grade, architecture, necrosis, receptors, margins (after excision), and more. Ask for a plain-language walkthrough of your report.

IHC (immunohistochemistry)

Lab staining methods used to test for receptors such as ER, PR, and HER2 on tissue samples.

UOQ (upper outer quadrant)

A common way to describe location in the breast (clock-face or quadrant language on imaging and path reports).

Extent / multifocal disease

How much breast is involved and whether there are multiple separate areas. Large or multifocal disease can change surgery options (conservation vs mastectomy).

Imaging & biopsy

Mammogram

X-ray of the breast. Screening mammograms look for disease without symptoms; diagnostic mammograms evaluate a finding in more detail.

BI-RADS

Standardized breast imaging reporting categories (0–6) that communicate how suspicious a finding is and what next step is recommended (e.g. callback, biopsy).

Ultrasound

Sound-wave imaging often used with mammogram to characterize masses or guide biopsy. Less sensitive alone for some calcifications.

Breast MRI

Magnetic resonance imaging of the breast. Sometimes used to estimate extent of disease or screen high-risk patients. Not required for everyone with DCIS.

Dense breast tissue

Breasts with more fibroglandular tissue relative to fat. Density can hide findings on mammogram and may influence supplemental imaging discussions.

Core biopsy

Removal of small tissue cores through a needle for pathology. Standard way DCIS is first diagnosed after imaging. Samples only part of a lesion.

Stereotactic biopsy

A type of image-guided core biopsy (often for calcifications) using mammographic targeting.

Biopsy marker (clip)

A small marker left after biopsy so the site can be found later on imaging or for surgery.

Imaging–pathology concordance

Whether the biopsy result “fits” what imaging expected. Discordance may lead to more sampling or surgery.

Treatment building blocks

Standard of care (SOC)

Approaches most widely recommended in guidelines and practice for a condition. For many people with DCIS this includes local treatment (surgery ± radiation) and, if hormone-receptor positive, discussion of endocrine therapy — individualized by your team.

Local control / local therapy

Treatment aimed at the breast (and sometimes nodes): surgery and/or radiation, as opposed to whole-body (systemic) therapy.

Breast-conserving surgery (BCS) / lumpectomy

Surgery that removes the DCIS area with a rim of surrounding tissue, aiming to keep most of the breast. Also called partial mastectomy in some settings.

Mastectomy

Surgery removing more or all breast tissue. Considered for extensive disease, inability to clear margins, risk reduction, preference, or other clinical reasons. Reconstruction may be discussed.

Margins

How close DCIS cells are to the edge of removed tissue. Clear (negative) margins are a common goal after lumpectomy. Positive or inadequate margins may lead to re-excision or further treatment discussion.

Re-excision

A second surgery to remove more tissue when margins are not adequate.

Oncoplastic surgery

Combines cancer removal with plastic-surgery techniques to reshape the breast after conservation when appropriate.

Sentinel lymph node biopsy

Sampling of the first draining lymph node(s). Not routine for pure DCIS on core biopsy alone; more often discussed if invasion is found or with mastectomy in some protocols.

Radiation therapy (RT)

High-energy treatment to the breast (or part of the breast) after lumpectomy to lower the chance of DCIS or invasive cancer returning in that breast. Benefit is mainly local control; survival impact for typical DCIS is usually small or not shown.

Whole-breast vs partial-breast radiation / boost

Whole-breast treats most of the breast; partial-breast treats a smaller region in selected patients. A boost is extra dose to the lumpectomy bed in some plans.

DCISionRT (and similar tools)

A commercial genomic/biosignature test on DCIS tissue that some teams use to estimate radiation benefit after surgery. Not universal; ask radiation oncology whether it applies to you.

Oncotype DX DCIS Score (and related)

Another genomic score studied in DCIS for recurrence risk discussions. Availability and use vary by center and era of guidelines.

Adjuvant therapy

Treatment given after primary local therapy (e.g. radiation or endocrine therapy after surgery) to reduce future risk.

Surveillance

Scheduled follow-up exams and imaging after (or instead of, in selected monitoring protocols) treatment to look for new or recurrent disease.

De-escalation

Intentionally using less intensive treatment (e.g. omitting radiation or endocrine therapy) when absolute risks and values support it, usually after shared decision. Not risk-free and not appropriate for everyone.

Active monitoring / active surveillance

Close imaging and clinical follow-up without immediate surgery, studied mainly for selected low-risk DCIS (e.g. COMET-style eligibility). Intermediate/high-risk features often exclude this path. Longer-term data still maturing.

Hormones & receptors

ER (estrogen receptor)

Protein on cells that can bind estrogen. ER-positive (ER+) DCIS is often considered for endocrine (hormone-blocking) therapy. Percent and intensity may be reported (e.g. “90% strong”).

PR (progesterone receptor)

Related hormone receptor. Often reported with ER. PR+ status contributes to the hormone-receptor profile.

HR+ (hormone-receptor positive)

Shorthand for ER+ and/or PR+ disease. Endocrine therapy discussions are common in this group.

HER2

A growth-factor receptor tested by IHC and/or other methods. Critical in invasive breast cancer pathways; for pure DCIS, reporting and implications vary — confirm status and meaning with your team.

Endocrine therapy (hormone-blocking therapy)

Medicines that block estrogen’s effect or lower estrogen production (e.g. tamoxifen, aromatase inhibitors). In ER+ DCIS, used mainly to reduce future breast events in either breast, not usually framed as large survival rescue for stage 0.

Tamoxifen

A selective estrogen receptor modulator used in many ER+ breast settings, including DCIS after local treatment in classic trials (e.g. NSABP B-24). Side effects can include hot flashes and rare clot or uterine risks — discuss personal risk.

Aromatase inhibitor (AI)

Medicines (e.g. anastrozole, letrozole, exemestane) that lower estrogen production, used mainly after menopause (or with ovarian suppression). Studied in DCIS (e.g. IBIS-II, NSABP B-35 contexts). Bone and joint effects are common topics.

HRT / MHT (hormone replacement / menopausal hormone therapy)

Systemic estrogen ± progestogen (± other hormones) used for menopause symptoms or other indications. Can conflict with endocrine blockade goals in HR+ disease; timing (pause, stop, restart) needs an explicit plan with oncology and other clinicians. See also this site’s estrogen literacy materials.

Menopausal status

Whether ovaries have stopped producing significant estrogen. Affects which endocrine agents are appropriate and how side effects are managed.

Risk language & decision terms

Absolute risk

Risk stated as a concrete chance (e.g. “about 5 in 100 over 10 years”). Best for comparing options. Prefer absolute numbers over relative phrases alone.

Relative risk

Change expressed as a ratio or percent reduction (e.g. “50% lower”). Can sound large when absolute benefit is modest. Always ask for absolute percentages too.

Ipsilateral

Same side / same breast as the original DCIS.

Contralateral

Opposite breast. Endocrine therapy can affect risk of new events in either breast.

Local recurrence / breast event

Return of DCIS or invasive cancer in the treated breast (or nearby). Distinct from distant metastasis, which is uncommon after treated pure DCIS in population data but not impossible after invasive disease.

Shared decision-making

Collaborative process: clinicians provide options and absolute risks; you contribute values and goals; the plan is agreed and documented together.

Second opinion / pathology review

Another specialist (or central pathology lab) re-reviews imaging, path, or plan. Often useful before irreversible choices or when considering de-escalation.

Tyrer-Cuzick (and other risk models)

Tools estimating lifetime or short-term breast cancer risk from personal and family factors. They inform screening intensity; they do not replace pathology of an existing DCIS.

Germline genetic testing

Blood or saliva testing for inherited variants (e.g. BRCA1/2, PALB2, CHEK2, ATM, TP53) that can raise cancer risk. Guidelines consider age, family history, and tumor context — not only “strong family history.”

Non-inferiority

Trial design showing a new approach is “not unacceptably worse” than standard on a chosen endpoint within a pre-set margin. Short-term non-inferiority is not a lifetime guarantee.

Trials & research terms

Clinical trial

A structured research study with eligibility rules, informed consent, and defined procedures. Participation is optional. Trials generate evidence; they are not automatically “better care.”

COMET (NCT02926911)

Major U.S. trial comparing active monitoring vs guideline care in selected women with low-risk hormone-receptor–positive DCIS. Short-term results informed the monitoring debate; longer follow-up continues. Eligibility is specific — not all DCIS qualifies.

DCIS RECAST (and related)

Research efforts refining who might safely use active surveillance or related strategies. Check ClinicalTrials.gov for current status and criteria.

LUMINA (and related omission studies)

Research contexts exploring reduced treatment (including radiation omission) in carefully defined lower-risk groups. Not a free pass for all DCIS; ask whether any study applies to you.

NSABP B-24 / B-35

Landmark cooperative-group trials informing endocrine therapy after local treatment for DCIS (tamoxifen; later AI vs tamoxifen comparisons). Often cited when discussing hormone blockade.

RTOG 9804

Trial of radiation in “good-risk” DCIS after lumpectomy; long-term data show lower local recurrence with radiation and little survival difference — frequently cited in radiation decisions.

SEER

U.S. cancer registry system used in population studies (including long-term mortality after DCIS). Population averages are not individual predictions.

Overtreatment / undertreatment

Concern that some people receive more treatment than needed for their risk (overtreatment), or too little (undertreatment). Much modern DCIS research aims to risk-adapt between those poles.

Care team roles

Breast surgical oncologist

Surgeon specializing in breast cancer operations and local treatment planning (lumpectomy, mastectomy, nodes, coordination with other specialists).

Radiation oncologist

Physician who plans and delivers radiation therapy and discusses absolute benefit vs burden for your pathology.

Medical oncologist

Physician focused on systemic therapy (including endocrine therapy) and overall cancer medicine strategy.

Nurse navigator / care navigator

Clinician who helps schedule, coordinate, and explain next steps across the care path.

PCP (primary care clinician)

Your regular doctor or advanced practice clinician — important for overall health, bones, hormones, and long-term follow-up alongside oncology.

Pathologist / radiologist

Pathologist interprets tissue. Radiologist interprets imaging and often performs image-guided biopsy. Both reports drive decisions.

Genetic counselor

Specialist who assesses hereditary risk, explains testing options, and interprets germline results in family context.

Organizations & sources (short)

NCI (National Cancer Institute)

U.S. federal cancer research institute. PDQ summaries are widely used patient and professional references.

ACS (American Cancer Society)

Major nonprofit providing patient-facing education on cancer types and treatments, including DCIS.

NCCN

National Comprehensive Cancer Network — publishes widely used oncology guidelines and patient guideline booklets.

ASCO / ASCO Post

American Society of Clinical Oncology and its news/analysis outlet covering trials and practice debates.

BCRF

Breast Cancer Research Foundation — research funding organization with plain-language disease overviews.

ClinicalTrials.gov

U.S. registry of clinical studies. Search by condition (DCIS), drug, or NCT number (e.g. NCT02926911 for COMET).

PubMed

Searchable index of biomedical literature. Best used with clinician help for applying papers to an individual case.

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Related on this site

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