[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Chest · Female](https://durgical.com/en/anatomy/region/chest/) › Mammary gland lobes [Skin](https://durgical.com/en/anatomy/system/skin/) · [Chest · Female](https://durgical.com/en/anatomy/region/chest/) # Mammary gland lobes The mammary gland lobes are the milk-making sections of the breast, arranged around the [nipple](https://durgical.com/en/anatomy/nipple/); their lobules make milk, and many breast cancers start there. Official name: Mammary gland [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=thorax&variant=female&select=mammary_lobes&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The milk-making gland of the breast: 15 to 20 lobes, each made of many small lobules, set in fat. It lies over the pectoralis major from the 2nd to the 6th rib, with a tail that reaches toward the armpit (the axillary tail). ## What it does The lobules make milk after childbirth; the gland changes with the menstrual cycle, pregnancy and menopause. ## Key points - Most breast cancers start in the terminal duct lobular unit, the junction of the smallest duct and its lobule - The axillary tail passes through an opening in the deep fascia into the axilla, next to the pectoral lymph nodes; it can be mistaken for an axillary lump - Axillary nodes are staged by their relation to the [pectoralis minor](https://durgical.com/en/anatomy/pectoralis-minor-muscle/): level I below and lateral to it, level II behind it, level III above and medial to it ## Key facts **Where** On pectoralis major and serratus anterior, from rib 2 to 6 and from the sternum to the mid-axillary line, with an axillary process **Blood supply** Internal thoracic (medial), lateral thoracic and thoracoacromial (lateral) arteries; intercostal perforators **Nerve** Anterior and lateral cutaneous branches of [intercostal nerves](https://durgical.com/en/anatomy/intercostal-nerves/) T4–T6 (nipple: T4) **Function** 15–20 lobes of lobules (terminal duct lobular units) that make milk; lymph about 75% to axillary nodes, the rest mainly to parasternal nodes ## Relations **Deep** [Retromammary space](https://durgical.com/en/anatomy/pectoral-fascia/), then the pectoral fascia over the [pectoralis major](https://durgical.com/en/anatomy/pectoralis-major-muscle/) (most of the base), the [serratus anterior](https://durgical.com/en/anatomy/serratus-anterior/) laterally and the [external oblique](https://durgical.com/en/anatomy/external-abdominal-oblique-muscle/) aponeurosis below **Lateral** Axillary tail running up toward the axilla and its lymph nodes, beside the lower border of the pectoralis major **Below** Inframammary fold, where the lower edge of the breast meets the [chest](https://durgical.com/en/anatomy/region/chest/) wall, at about the 6th rib **Medial** Edge of the [sternum](https://durgical.com/en/anatomy/sternum/); the [parasternal lymph nodes](https://durgical.com/en/anatomy/parasternal-nodes/) lie deeper, along the [internal thoracic artery](https://durgical.com/en/anatomy/internal-thoracic-artery/) ## How to find it Positions are described by four quadrants, divided by a horizontal and a vertical line through the nipple, plus the central subareolar part and the axillary tail; a finding is also given as a clock position and its distance from the nipple. The upper outer quadrant holds the most gland and is where most cancers are found. ## Examination - Inspection seated, arms at the sides, then raised, then hands pressed on the hips to tense the pectoralis major: asymmetry, a bulge, dimpling or a change in contour becomes visible - Palpation lying down with the arm on that side raised, so the breast flattens on the chest wall; the whole area, from the [clavicle](https://durgical.com/en/anatomy/clavicle/) to the inframammary fold and from the sternum to the mid-axillary line, is covered in vertical strips, then the axillary and supraclavicular nodes ## On imaging Mammography takes two standard views per breast: craniocaudal and mediolateral oblique; the oblique view includes the axillary tail and the pectoralis muscle. Ultrasound is first choice in young or pregnant women and tells a cyst from a solid lump. Reports use BI-RADS, a standard set of assessment categories from 0 to 6 plus a density grade. ## Common problems - Benign lumps: fibroadenoma (a firm, mobile lump, common in young women) and cysts. - Fibrocystic changes: lumpy, tender breasts before a period. - Lobular carcinoma: a cancer that starts in the lobules; it can be harder to feel and to see on a mammogram. - Most gland tissue, and most cancers, sit in the upper outer quadrant, toward the armpit. ## How it is diagnosed Clinical breast exam, mammography, ultrasound (young or dense breasts) and a core-needle biopsy of any suspicious lump. ## Treatment - Benign lumps: watchful follow-up, or removal if they grow. - Cancer: breast-conserving surgery (lumpectomy) or mastectomy, usually with a sentinel lymph node biopsy, then radiotherapy, hormone therapy or chemotherapy as needed. ## Clinical notes - Fibroadenoma, a common benign tumour of the lobule's stroma and lining in young women, is a smooth, rubbery lump that moves easily under the fingers - Medial tumours can drain to the parasternal lymph nodes, which sentinel node biopsy and axillary surgery do not reach - Screening mammography lowers breast cancer deaths; the starting age and interval differ between guidelines and countries - The lobules grow in pregnancy and lactation and involute after menopause, which changes how the breast feels and looks on imaging ## Anatomical variants - Accessory breast tissue, most often in the axilla, can swell and become tender in pregnancy and lactation - Some asymmetry between the two breasts is common and normal ## Development The ducts grow at puberty under oestrogen (thelarche, usually the first sign of puberty in girls, staged by Tanner), and the lobules develop further with progesterone and fully in pregnancy. ## Related conditions - [Hereditary breast and ovarian cancer syndrome (BRCA1/BRCA2)](https://durgical.com/en/conditions/hereditary-breast-and-ovarian-cancer-syndrome/) - [Breast cancer](https://durgical.com/en/conditions/breast-cancer/) - [Breast fibroadenoma](https://durgical.com/en/conditions/breast-fibroadenoma/) - [Acute mastitis](https://durgical.com/en/conditions/acute-mastitis/) - [Breast abscess](https://durgical.com/en/conditions/breast-abscess/) - [Fibrocystic breast changes](https://durgical.com/en/conditions/fibrocystic-breast-changes/) ## Test yourself Think of the answer, then tap the question to see it. ## In which part of the mammary gland do most breast cancers start? In the terminal duct lobular unit, the junction of the smallest duct and its lobule. ## Which breast quadrant holds the most gland tissue, and where are most cancers found? The upper outer quadrant, toward the axilla, holds the most gland, and most cancers are found there. ## How are axillary lymph node levels defined? By the pectoralis minor: level I below and lateral to it, level II behind it, level III above and medial to it. ## Where does lymph from the mammary gland drain, and why do medial tumours matter? About 75% to the axillary nodes, the rest mainly to the parasternal nodes; medial tumours can drain there, beyond reach of sentinel node biopsy. ## What are the features of a fibroadenoma? A common benign tumour of the lobule's stroma and lining in young women: a smooth, rubbery lump that moves easily under the fingers. [Add to my cards (5)](https://durgical.app/estudiar/?add=/en/anatomy/mammary-gland/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** glandula mammaria; lobi glandulae mammariae TA2 7099 **Official Spanish (DeCS)** Lóbulos de la glándula mamaria DeCS D042361 **English (TA2)** Mammary gland Sources: Terminologia Anatomica (TA2); [DeCS](https://decs.bvsalud.org/es/ths/resource/?id=37753&filter=ths_termall&q=Gl%C3%A1ndulas%20Mamarias%20Humanas); [Anatomy, Thorax, Breast](https://www.ncbi.nlm.nih.gov/books/NBK519575/); [Anatomy, Thorax: Mammary Gland](https://www.ncbi.nlm.nih.gov/books/NBK547666/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/mammary-gland/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/mammary-gland/