🌸 Benign Breast Disease (Fibroadenoma vs Cyst) Simulator

A Palpable Breast Mass Is Found

Most breast lumps in young women are benign.

• ~90%: Benign mass rate under 40 (of palpable lumps)
• Fibroadenoma: Most common solid mass (peak age 15–35)
• Simple cyst: Most common cystic mass (peak age 35–50)
• Ultrasound: Initial workup step (first-line under 30)

How masses are first found

Self-exam, clinical exam, or routine screening detects a lump.

Two dominant benign causes

Fibroadenoma (solid fibrous gland) and simple cyst (fluid sac) top the list.

Cancer accounts for a small minority of palpable masses in younger patients.

Why differentiation matters

Correct triage avoids unnecessary biopsy and catches true suspicious lesions.

Mobility on Palpation — the "Breast Mouse" Sign

How a mass moves under the finger hints at its composition.

• High: Fibroadenoma mobility (classic "breast mouse")
• Moderate–low: Simple cyst mobility (tethered by ducts)
• Smooth, round: Fibroadenoma borders (well-circumscribed)
• Fluctuant: Cyst consistency (compressible on exam)

The breast mouse sign

A fibroadenoma slides freely between the fingers, unattached to tissue.

Cyst tethering

A simple cyst moves less, feels fluctuant, sometimes tender.

Mobility alone is suggestive, never diagnostic on its own.

Limits of palpation

Deep or small masses may feel identical — imaging confirms the difference.

Solid Versus Cystic Appearance on Ultrasound

Ultrasound is the definitive tool for solid-vs-cystic sorting.

• Homogeneous: Fibroadenoma echo pattern (low-level internal gray)
• Anechoic: Simple cyst echo pattern (pure black, no echoes)
• Enhancement: Cyst posterior feature (brightening behind mass)
• Oval, wider-than-tall: Fibroadenoma shape (gently lobulated)

Solid mass texture

Fibroadenomas show uniform gray internal echoes throughout.

Cystic mass texture

Simple cysts appear anechoic black with a thin, sharp wall.

Posterior acoustic enhancement behind a mass confirms fluid content.

Complex or mixed cases

Internal septations or debris push a cyst toward further workup.

Elastography — Mapping Tissue Stiffness

Elastography colors tissue by how much it deforms under pressure.

• Firm: Fibroadenoma stiffness (moderate elastic score)
• Soft: Simple cyst stiffness (fully compressible)
• Blue = soft: Color convention (red = stiff)
• Very stiff: Suspicious lesion stiffness (red, non-compressible)

How elastography works

Gentle compression measures tissue displacement to score stiffness.

Reading the color map

Blue overlay marks soft cystic fluid; red marks firmer solid tissue.

A fully soft, blue, compressible mass strongly favors a simple cyst.

Adjunct, not replacement

Elastography adds confidence but pairs with grayscale ultrasound.

Assigning a Benign BI-RADS Category

Mobility, echo pattern, and stiffness combine into one category.

• BI-RADS 2: Simple cyst category (benign)
• BI-RADS 3: Classic fibroadenoma (probably benign)
• BI-RADS 4: Atypical solid mass (needs biopsy)
• 6 months: BI-RADS 3 follow-up (short-interval imaging)

Category 2 — benign

A simple, anechoic, soft, mobile cyst needs no further action.

Category 3 — probably benign

A classic solid, mobile, homogeneous fibroadenoma gets short-interval follow-up.

Category 3 carries under 2% malignancy risk — biopsy is optional.

When features disagree

Non-mobile, stiff, or irregular solid masses escalate toward biopsy.