12.1 Benign Pathology and Mammographic Appearance

Why Benign Pathology Is a Procedures Item

ARRT Mammography Procedures 1.E.2 asks you to recognize the mammographic appearance of named benign entities and to know what usually happens next — ultrasound, additional views, clinical correlation, or no further action when the look is classic. You are not the interpreting physician. You document, mark, position, and flag. The radiologist assigns a BI-RADS assessment. That split matters on the exam: a question about a round equal-density mass is testing whether you know it still needs ultrasound, not whether you would call it BI-RADS 2 yourself.

History is part of the image. Lactation, a seat-belt injury, a lumpectomy scar, a male patient with a tender ridge behind the nipple, and new unilateral redness all change how the same density should be handled. Place a scar marker, mole marker, or palpable-lump marker when the facility protocol calls for it, and write the clinical note the radiologist will actually read.

Circumscribed Masses: Cyst, Galactocele, Fibroadenoma

Cyst

A simple cyst is a fluid-filled, epithelial-lined space. On mammography it is a round or oval, circumscribed, equal- or low-density mass. Margins may be partly obscured by overlapping parenchyma. That description also fits a fibroadenoma, a papilloma, a complicated cyst, and some cancers, so mammography does not prove a lesion is a cyst. Ultrasound is the usual next step. A simple cyst is anechoic, thin-walled, and shows posterior acoustic enhancement; those lesions are typically left alone (no biopsy). A complicated cyst (internal echoes) may be followed. A complex cystic-and-solid mass is not treated as a simple cyst — it is worked up as a potentially solid lesion.

Galactocele

A galactocele is a milk-filled retention cyst in a woman who is lactating or recently lactating. It is one of the few benign masses that can look fat-containing on mammography. The teaching view is a fat-fluid level on a true 90-degree lateral (milk fat rises). Ultrasound shows a cystic or mixed cystic-solid mass. Correlate with breastfeeding or weaning; do not send a lactating patient through screening as if the finding were unexplained. If the look is not classic, ultrasound-guided sampling may still be needed.

Fibroadenoma

A fibroadenoma is a fibroepithelial solid mass, most often in younger patients. Mammography: oval, circumscribed, equal-density, typically oriented with its long axis parallel to the chest wall. As it involutes, it can develop coarse popcorn calcifications that are typically benign. Ultrasound: solid, parallel, gently lobulated, with a thin echogenic capsule. A new, enlarging, or atypical fibroadenoma-like mass is not assumed benign — phyllodes tumor (Section 12.2) can mimic it, so growth is a reason to biopsy rather than to "watch a fibroadenoma."

Fat-Containing Lesions: Lipoma, Hamartoma, Fat Necrosis

Lipoma

A lipoma is a mature fat mass with a thin capsule. It is radiolucent (fat density) relative to fibroglandular tissue. If the capsule is thin and the interior is uniformly fat, the usual next step is no further imaging. A mixed-density encapsulated mass is not called a simple lipoma.

Hamartoma

A hamartoma (fibroadenolipoma) is a benign disorganized mix of fat, glandular tissue, and fibrous tissue inside a capsule. The classic mammographic phrase is "breast within a breast": an encapsulated island of mixed fat and fibroglandular density sitting in the surrounding breast. When that look is classic, it is typically left alone. If the capsule is incomplete, the interior looks like a dense mass without fat, or the finding is new and not fat-containing, ultrasound and possible biopsy follow.

Fat necrosis

Fat necrosis follows surgery, trauma, reduction mammoplasty, reconstruction, or radiation. Early, it can be an irregular or spiculated density and can mimic cancer — history and a scar marker are essential. Later it may form a lucent oil cyst, then rim or coarse dystrophic calcifications. A classic oil cyst with rim calcifications is typically watched. An irregular density without a matching surgical or trauma story is not called fat necrosis by the technologist; it is flagged for diagnostic workup.

Ductal and Inflammatory Benign Entities

Papilloma

An intraductal papilloma is a benign epithelial growth inside a duct, often central / retroareolar. The clinical clue is spontaneous unilateral bloody or clear nipple discharge. Mammography is frequently normal or shows only a small subareolar mass or a dilated duct. Ultrasound (sometimes ductography) is the usual next step. Solitary papillomas without atypia are still diagnosed histologically, not by the mammogram. Papilloma with atypia belongs with upgrade-risk lesions in 12.2.

Duct ectasia

Duct ectasia is dilatation of major retroareolar ducts, often with inspissated secretions. Mammography: tubular retroareolar lucencies or densities; calcifications, when present, are often large rod-like (secretory) and point toward the nipple — a typically benign BI-RADS morphology. Discharge, if present, is more often thick and green or black than frankly bloody. Classic secretory calcifications are usually ignored; a new mass or suspicious calcifications are not blamed on ectasia.

Hematoma

A hematoma is a blood collection after trauma, biopsy, or surgery. Acute mammography shows a new, often ill-defined density at the site. Over days to weeks it may evolve into a seroma or an oil cyst. The technologist's job is to record the date and site of injury or intervention and to mark the skin entry or scar. Without that history, the same density is just a new mass.

Abscess and inflammation

Mastitis and abscess present with pain, warmth, erythema, and often fever. Mammography (when it can be tolerated) may show skin thickening, trabecular thickening, and a focal density or mass. This is a diagnostic problem, not a screening one. Ultrasound looks for a drainable collection and guides aspiration. The dangerous overlap is inflammatory carcinoma (Section 12.4): infection that does not improve after a short, documented antibiotic course is not assumed to be "just mastitis."

Nodes, the Male Breast, Fluid, and Diffuse Change

Lymph nodes

Intramammary lymph nodes are common in the upper outer quadrant and axillary tail. Classic look: small reniform (kidney-bean) density with a fatty hilum, often a lucent notch. Axillary nodes on the MLO should be inspected the same way. A node that becomes round, dense, and hilum-poor, or that develops a thickened cortex on ultrasound, is flagged. Silicone from an extracapsular implant rupture can produce dense axillary nodes; document implant history.

Gynecomastia

Gynecomastia is benign male ductal and stromal proliferation. Mammography: a flame-shaped or triangular density centered directly behind the nipple, often tender, often bilateral even when the patient feels only one side. Male breast cancer more often presents as an eccentric (not nipple-centered) irregular mass and may have spiculation, calcifications, or adenopathy. Do not crop the posterior nipple line on a male MLO; the distinction lives in that retroareolar tissue.

Edema

Edema produces diffuse trabecular thickening, skin thickening, and an overall increase in breast density. Bilateral edema suggests a systemic cause (congestive heart failure, hypoalbuminemia, nephrotic syndrome) or dependent change. Unilateral edema raises local causes: mastitis, radiation, lymphatic obstruction, axillary dissection, and inflammatory carcinoma. Laterality and the clinical note are the interpretation.

Seroma

A seroma is a postoperative serum collection at a lumpectomy, mastectomy, or reconstruction bed. Mammography: a circumscribed, water-density oval or round collection at the surgical site. Ultrasound confirms fluid. An expected, stable postoperative seroma is typically observed. A rapidly enlarging, tense, or infected collection may need drainage — that decision is clinical, but the technologist still documents size change and symptoms.

Recognition Table (Entity → Look → Next Step)

Exam trap: "Circumscribed" is not a synonym for "benign." Mucinous and papillary cancers, and some metastases, can be round and well-defined. The technologist's safe move is always the same: excellent positioning, complete history, and the next test the protocol names — usually ultrasound for a mass, diagnostic views for calcifications or distortion.