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Breast Imaging – FRCR 2A Radiology Question Bank

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Question 1: Benign Calcifications

Stem: A 62-year-old woman attends routine breast screening. The mammogram is unremarkable apart from a small group of calcifications in the right breast. The magnification views (CC and 90-degree lateral) demonstrate that these are crescent-shaped, lucent-centred, and “layer” on the lateral view, forming a “tea-cup” appearance.

Question: What is the most likely diagnosis for these calcifications?

(A) Milk of Calcium (B) Ductal Carcinoma In Situ (DCIS) (C) Vascular Calcifications (D) Fat Necrosis (Oil Cyst) (E) Skin Calcifications

Correct Answer: (A) Milk of Calcium.

Explanation:

  • Why (A) is correct: Milk of calcium is the classic description for sedimented calcifications within benign microcysts. They are lucent-centred and, critically, they are mobile. This mobility and layering are proven on the 90-degree lateral view, where they “fall” to the dependent portion of the cyst, forming “tea-cup” or crescent-shapes. This is a definitively benign (BI-RADS 2) finding.
  • Why (B) is wrong: DCIS is the primary differential for suspicious calcifications. However, DCIS calcs are typically pleomorphic (varying shapes/sizes), fine, and linear-branching (filling a duct), not crescent-shaped and layering.
  • Why (C) is wrong: Vascular calcifications are coarse, linear, and “tram-track” in appearance, clearly following the path of a blood vessel.
  • Why (D) is wrong: Fat necrosis can cause coarse or rim calcifications (an “oil cyst”), but not the fine, sedimented appearance of milk of calcium.
  • Why (E) is wrong: Skin calcifications are lucent-centred but are located in the dermis and can be confirmed by their peripheral location or by using skin-marking (tangential) views.

Key Points: Milk of Calcium

  • Pathology: Calcium sediment within benign acini/microcysts.
  • Mammography: Appears as faint, lucent-centred, or amorphous smudges on the CC view.
  • Key Sign (90-degree Lateral): The calcifications layer dependently, forming “tea-cup” or crescent shapes.
  • BI-RADS: BI-RADS 2 (Benign). No further action needed.

Question 2: Malignant Calcifications (DCIS)

Stem: A 55-year-old woman is recalled from screening for a new group of calcifications in the left upper quadrant. Magnification views show a 3 cm, linear, and branching (ductal) distribution of fine, pleomorphic calcifications (meaning they vary in size and shape).

Question: This pattern of calcification is most suspicious for:

(A) Ductal Carcinoma In Situ (DCIS) (B) Milk of Calcium (C) Fibroadenoma with “popcorn” calcification (D) Fat Necrosis (E) Sclerosing Adenosis

Correct Answer: (A) Ductal Carcinoma In Situ (DCIS).

Explanation:

  • Why (A) is correct: The combination of fine, pleomorphic calcifications (variable, irregular, “crushed stone” appearance) with a linear-branching or segmental distribution (following a duct system) is the classic, highly suspicious appearance of DCIS.
  • Why (B) is wrong: Milk of calcium is benign and has a “tea-cup” appearance on lateral views.
  • Why (C) is wrong: A fibroadenoma is a mass, and when it calcifies, it forms large, coarse, “popcorn-like” calcifications.
  • Why (D) is wrong: Fat necrosis causes dystrophic calcifications or classic “oil cysts,” which are lucent-centred and smooth-walled, not pleomorphic.
  • Why (E) is wrong: Sclerosing adenosis is a benign proliferative condition that can cause calcifications, but they are typically punctate (dot-like) and grouped, not linear and branching.

Key Points: Malignant Calcifications

  • Morphology (Shape):
    • Fine Pleomorphic: Irregular, varying in shape/size.
    • Fine Linear/Branching: Thin, branching, “casting” shapes. (Highest suspicion for DCIS).
  • Distribution:
    • Segmental: Fills a duct and its branches (points to the nipple).
    • Linear: In a line.
  • BI-RADS: BI-RADS 4C or 5. Requires biopsy (stereotactic vacuum-assisted biopsy).

Question 3: Invasive Ductal Carcinoma (IDC)

Stem: A 62-year-old woman presents with a new, hard, palpable lump in her right breast. A mammogram shows a 2 cm, high-density, irregular mass with spiculated margins. The corresponding ultrasound reveals an irregular, hypoechoic, “taller-than-wide” mass with posterior acoustic shadowing.

Question: These imaging features are most characteristic of:

(A) Invasive Ductal Carcinoma (IDC) (B) Fibroadenoma (C) Simple Cyst (D) Radial Scar (E) Haematoma

Correct Answer: (A) Invasive Ductal Carcinoma (IDC).

Explanation:

  • Why (A) is correct: This is the classic malignant presentation. Mammogram: High-density, irregular, spiculated margins (due to desmoplastic reaction). Ultrasound: Irregular, “taller-than-wide” (anti-parallel, breaching tissue planes), hypoechoic, with posterior acoustic shadowing (due to dense fibrous tissue). This is a BI-RADS 5 lesion.
  • Why (B) is wrong: A fibroadenoma is a benign mass, typically oval, well-circumscribed, and “wider-than-tall” (parallel to the skin).
  • Why (C) is wrong: A simple cyst is anechoic (black), thin-walled, and has posterior acoustic enhancement (brightness), not shadowing.
  • Why (D) is wrong: A radial scar is a “great mimic” and is also spiculated, but it classically has a lucent centre on mammography, not a high-density mass.
  • Why (E) is wrong: A haematoma is a post-traumatic fluid collection and would not be a spiculated, shadowing solid mass.

Key Points: Malignant Mass Features

  • Mammography (BI-RADS 5): High-density, spiculated margins, irregular shape.
  • Ultrasound (BI-RADS 5): Irregular shape, taller-than-wide orientation, indistinct/angular/spiculated margins, posterior acoustic shadowing.

Question 4: Invasive Lobular Carcinoma (ILC)

Stem: A 68-year-old woman presents with a vague, palpable “thickening” in her left breast. A mammogram is performed, which is interpreted as normal. Due to high clinical suspicion, an ultrasound is done, which is also inconclusive, showing only a vague area of “shadowing without a discrete mass.” A breast MRI is finally performed.

Question: Which of the following findings on MRI is the classic pattern for Invasive Lobular Carcinoma (ILC)?

(A) A focal, 2 cm, intensely enhancing mass with washout. (B) A linear, non-mass-like enhancement in a “single-file” or “sheet-like” pattern. (C) A microcystic, “honeycomb” mass with a central scar. (D) A T1-bright, non-enhancing mass with fat suppression. (E) No enhancement at all.

Correct Answer: (B) A linear, non-mass-like enhancement in a “single-file” or “sheet-like” pattern.

Explanation:

  • Why (B) is correct: ILC is the “great mimic” and “stealth” lesion. Its cells grow in “single-file” lines and do not form cohesive masses or incite a strong fibrotic reaction. Therefore, it is often occult on mammography (“shrinking breast,” architectural distortion only) and US (“shadowing without mass”). MRI is the most sensitive test, where it classically appears as non-mass-like enhancement (NME) in a segmental or linear, “single-file” pattern.
  • Why (A) is wrong: This is a classic description of a focal Invasive Ductal Carcinoma (IDC).
  • Why (C) is wrong: This describes a serous cystadenoma of the pancreas, not a breast lesion.
  • Why (D) is wrong: This describes a dermoid cyst (fat-containing).
  • Why (E) is wrong: ILC is a cancer and will enhance avidly; if it doesn’t enhance, it’s not cancer.

Key Points: Invasive Lobular Carcinoma (ILC)

  • Second most common type of invasive breast cancer.
  • Pathology: Cells infiltrate in a “single-file” pattern (loss of E-cadherin).
  • Imaging:
    • Mammo: Often occult. Classic signs are architectural distortion or focal asymmetry.
    • US: Often occult. Classic sign is shadowing without a discrete mass.
    • MRI: Most sensitive. Classic sign is non-mass-like enhancement (NME) in a linear/segmental pattern.

Question 5: Radial Scar

Stem: A 52-year-old woman is recalled from screening for an abnormality. A mammogram shows a 1.2 cm lesion with long, thin spicules radiating from a central, lucent core. There is associated architectural distortion. No discrete mass is seen on ultrasound, only a vague, shadowing area.

Question: This appearance is most characteristic of:

(A) Radial Scar / Complex Sclerosing Lesion (B) Invasive Ductal Carcinoma (C) Fat Necrosis (D) Haematoma (E) Simple Cyst

Correct Answer: (A) Radial Scar / Complex Sclerosing Lesion.

Explanation:

  • Why (A) is correct: A radial scar is a “great mimic” of cancer. The key differentiating feature is the central, lucent (dark) core on mammography. Cancer (IDC) typically has a high-density central mass. A radial scar is a benign, proliferative lesion, but it is always biopsied.
  • Why (B) is wrong: IDC is the main differential, but it classically has a dense centre, not a lucent one.
  • Why (C) is wrong: Fat necrosis can be spiculated, but it is usually post-traumatic and more likely to present as a lucent “oil cyst.”
  • Why (D) is wrong: A haematoma is a collection of blood and would not form a spiculated, lucent-centred lesion.
  • Why (E) is wrong: A cyst is a round, fluid-density mass that displaces tissue, not a spiculated lesion that tethers it.

Key Points: Radial Scar

  • Definition: A benign (B3), proliferative lesion of unknown cause (also called a Complex Sclerosing Lesion if >1 cm).
  • Mammography (Classic Sign): Spiculated lesion with a central lucent core.
  • Ultrasound: Often occult or appears as a non-specific, shadowing, irregular mass (mimicking cancer).
  • Management: Must be biopsied (typically with a vacuum-assisted biopsy) as it can be associated with tubular carcinoma or DCIS.

Question 6: Fat Necrosis / Oil Cyst

Stem: A 50-y/o woman, 1 year post-lumpectomy and radiation therapy, presents with a new, non-tender, palpable lump. The mammogram shows a 2 cm, round, lucent-centred lesion with a thin, “egg-shell” calcified rim.

Question: This finding is pathognomonic for:

(A) Fat Necrosis (Oil Cyst) (B) Tumour Recurrence (C) Seroma (D) Foreign Body (e.g., surgical clip) (E) Milk of Calcium

Correct Answer: (A) Fat Necrosis (Oil Cyst).

Explanation:

  • Why (A) is correct: This is the classic, pathognomonic, benign (BI-RADS 2) appearance of an oil cyst, which is a late-stage finding of fat necrosis. It is very common after trauma or, as in this case, surgery and radiation. The body walls off the liquefied fat, and the rim eventually calcifies (“egg-shell”).
  • Why (B) is wrong: Tumour recurrence would appear as a dense, spiculated mass or malignant calcifications, not a fat-filled, lucent cyst.
  • Why (C) is wrong: A seroma is a fluid-density (not fat-density) collection, and it typically resolves or has a thicker wall, not an “egg-shell” rim.
  • Why (D) is wrong: A surgical clip is metallic and has a distinct shape; it is not a 2 cm cyst.
  • Why (E) is wrong: Milk of calcium is sediment within tiny microcysts, not a large, fat-filled macrocyst.

Key Points: Fat Necrosis

  • Cause: Benign, inflammatory process, usually secondary to trauma, surgery, or radiation.
  • Variable Appearance:
    • Acute: Can mimic cancer, appearing as a spiculated, irregular mass.
    • Chronic (Classic): Evolves into a benign Oil Cyst (lucent centre, “egg-shell” calcified rim).
  • BI-RADS: A classic oil cyst is BI-RADS 2 (Benign).

Question 7: Simple vs. Complicated Cyst

Stem: A 48-year-old pre-menopausal woman presents for a screening mammogram (BI-RADS 0 – dense breasts) and is sent for a supplementary ultrasound. The ultrasound identifies a 1 cm, round, anechoic lesion with a thin, imperceptible wall and marked posterior acoustic enhancement.

Question: This ultrasound finding describes a simple cyst. What is the correct BI-RADS classification for this finding?

(A) BI-RADS 1 (B) BI-RADS 2 (C) BI-RADS 3 (D) BI-RADS 4 (E) BI-RADS 0

Correct Answer: (B) BI-RADS 2.

Explanation:

  • Why (B) is correct: BI-RADS 2 is for a Definitively Benign finding. A simple cyst, which meets all three criteria (anechoic, thin wall, posterior enhancement), is the textbook example of a BI-RADS 2 lesion. No follow-up is needed.
  • Why (A) is wrong: BI-RADS 1 means Negative (a completely normal exam with no findings). This exam has a finding (a cyst), so it is BI-RADS 2.
  • Why (C) is wrong: BI-RADS 3 means Probably Benign (<2% risk of malignancy) and requires short-term follow-up. This is used for lesions like a complicated cyst (e.g., with low-level internal echoes) or a typical fibroadenoma.
  • Why (D) is wrong: BI-RADS 4 means Suspicious and requires biopsy.
  • Why (E) is wrong: BI-RADS 0 means Incomplete (e.g., the mammogram that needs a supplementary ultrasound). The US itself provides the final answer.

Key Points: BI-RADS Ultrasound

  • Simple Cyst (BI-RADS 2): Must be Anechoic (pure black), have an imperceptible wall, and show posterior acoustic enhancement.
  • Complicated Cyst (BI-RADS 3): A cyst that fails one simple criterion, e.g., has low-level internal echoes (debris/protein) but no thick wall or solid component.
  • Complex Cystic Mass (BI-RADS 4/5): A cyst with a thick wall, thick septations, or a solid mural nodule.

Question 8: Inflammatory Breast Carcinoma

Stem: A 52-year-old woman presents with a 3-week history of a rapidly enlarging, painful, red, and warm right breast. She was prescribed a course of antibiotics for “mastitis” by her GP with no improvement. A mammogram confirms diffuse breast enlargement, significant skin thickening (> 2.5 mm), and trabecular thickening.

Question: The lack of response to antibiotics is a critical feature, making which diagnosis the most likely?

(A) Inflammatory Breast Carcinoma (B) Acute Mastitis / Abscess (C) Duct Ectasia (D) Lymphoma (E) Congestive Heart Failure

Correct Answer: (A) Inflammatory Breast Carcinoma.

Explanation:

  • Why (A) is correct: This is a clinical and radiological diagnosis of a highly aggressive cancer. It mimics infection (mastitis) but is caused by tumour emboli in the dermal lymphatics, leading to skin thickening (“peau d’orange”), erythema, and warmth. The key differentiator is the failure to respond to antibiotics.
  • Why (B) is wrong: Acute mastitis is the main differential, but it should respond to antibiotics. If it doesn’t, or if an abscess forms, it’s still inflammatory, but cancer must be ruled out.
  • Why (C) is wrong: Duct ectasia is a benign condition of ductal dilatation, not an acute inflammatory process.
  • Why (D) is wrong: Breast lymphoma is rare and presents as a mass, not typically an inflammatory picture.
  • Why (E) is wrong: CHF can cause bilateral oedema, but not a unilateral, red, hot breast.

Key Points: Inflammatory Breast Carcinoma

  • Definition: A clinical-pathological entity, not a histological type.
  • Pathology: Invasion of the dermal lymphatics by carcinoma (usually IDC).
  • Clinical: Mimics mastitis (red, swollen, warm, “peau d’orange” skin).
  • Key Differentiator: Does NOT respond to antibiotics.
  • BI-RADS: BI-RADS 5. A poor prognosis.

Question 9: Breast MRI Kinetics

Stem: A 60-y/o woman with a new BI-RADS 4 lesion on mammogram undergoes a breast MRI. A 1.5 cm mass is identified. Dynamic contrast-enhanced (DCE) curves are analysed. The lesion shows a slow, steady, progressive increase in signal intensity over the entire 8-minute post-contrast period.

Question: This kinetic curve (Type 1) is most reassuring and strongly suggests the lesion is:

(A) Benign (B) Malignant (C) Indeterminate (D) A simple cyst (E) Artefact

Correct Answer: (A) Benign.

Explanation:

  • Why (A) is correct: This describes a Type 1 (Progressive) enhancement curve. The signal intensity rises slowly and continuously. This pattern is associated with benign lesions (e.g., fibroadenomas, normal lymph nodes) in over 90% of cases, as they lack the “leaky” neovascularity and rapid washout of cancers.
  • Why (B) is wrong: Malignant lesions typically show rapid wash-in and either a Type 2 (Plateau) or, more specifically, a Type 3 (Washout) curve.
  • Why (C) is wrong: A Type 2 (Plateau) curve is considered indeterminate.
  • Why (D) is wrong: A simple cyst is a fluid-filled sac and would not enhance at all.
  • Why (E) is wrong: This is a standard kinetic curve type, not an artefact.

Key Points: MRI Kinetic Curves (DCE)

  • Type 1 (Progressive): Slow, continuous rise. Highly likely benign (>90%).
  • Type 2 (Plateau): Rapid rise, followed by a plateau. Indeterminate.
  • Type 3 (Washout): Rapid rise, followed by a decrease in signal. Highly suspicious for malignancy (>90%).
  • Note: Morphology (shape, margins) is more important than kinetics.

Question 10: Gynaecomastia

Stem: A 60-year-old man presents with a painful, palpable lump directly behind his left nipple. The mammogram reveals a symmetric, concentric, flame-shaped density in the subareolar region. No suspicious masses or calcifications are seen.

Question: What is the most likely diagnosis?

(A) Gynaecomastia (B) Male Breast Cancer (C) Pseudogynaecomastia (D) Lipoma (E) Abscess

Correct Answer: (A) Gynaecomastia.

Explanation:

  • Why (A) is correct: This is the classic, pathognomonic mammographic appearance of gynaecomastia (benign proliferation of glandular tissue). The key features are its symmetric, concentric (subareolar), and flame-shaped (or nodular/dendritic) appearance. It is often bilateral, even if only one side is symptomatic.
  • Why (B) is wrong: Male breast cancer is the key differential, but it is typically eccentric (off-centre), spiculated, and irregular, mimicking female IDC.
  • Why (C) is wrong: Pseudogynaecomastia is an accumulation of fat in the breast, which would appear lucent (dark), not as a glandular density.
  • Why (D) is wrong: A lipoma is a fat-containing mass (lucent) and would not be in this classic subareolar location.
  • Why (E) is wrong: An abscess is an inflammatory collection, not a flame-shaped density.

Key Points: Gynaecomastia vs. Male Breast Cancer

  • Gynaecomastia (Benign):
    • Location: Concentric (subareolar).
    • Shape: Nodular, dendritic, or flame-shaped.
    • Margins: Indistinct, but not truly spiculated.
  • Male Breast Cancer (Malignant):
    • Location: Eccentric (not centred on nipple).
    • Shape: Irregular, spiculated mass.
    • Associations: Suspicious calcifications, skin thickening.

Question 11: Implant Rupture (Intracapsular)

Stem: A 48-year-old woman with silicone breast implants undergoes an MRI for implant integrity. The right implant demonstrates an intact outer fibrous capsule, but the inner silicone shell is ruptured and has collapsed into the silicone gel. This appears as multiple, low-signal, curvilinear lines floating within the high-signal silicone.

Question: This MRI sign is pathognomonic for an intracapsular rupture and is known as the:

(A) “Linguine Sign” (B) “Snowstorm Sign” (C) “Stepladder Sign” (D) “Keyhole Sign” (E) “Salad Oil Sign”

Correct Answer: (A) “Linguine Sign”.

Explanation:

  • Why (A) is correct: The “linguine sign” is the pathognomonic MRI finding for an intracapsular silicone rupture. It represents the collapsed, crumpled inner implant shell floating freely within the silicone gel, resembling strands of linguine.
  • Why (B) is wrong: The “snowstorm sign” is the classic ULTRASOUND finding for an extracapsular rupture, representing free silicone in the breast tissue.
  • Why (C) is wrong: The “stepladder sign” is the classic ULTRASOUND finding for an intracapsular rupture, showing parallel lines (the folded shell).
  • Why (D) is wrong: The “keyhole sign” (or “noose sign”) is a sign of an uncollapsed intracapsular rupture.
  • Why (E) is wrong: The “salad oil sign” is not a standard term; it may refer to the mixing of saline and silicone in a double-lumen implant rupture.

Key Points: Implant Rupture (Silicone)

  • MRI is the gold standard.
  • Intracapsular Rupture: Fibrous capsule INTACT, inner shell RUPTURED.
    • MRI: “Linguine Sign” (collapsed shell).
    • US: “Stepladder Sign” (parallel lines).
  • Extracapsular Rupture: Both fibrous capsule and inner shell RUPTURED.
    • MRI: Free silicone in breast tissue (bright on silicone-only sequences).
    • US: “Snowstorm Sign” (echogenic noise from free silicone).

Question 12: Phyllodes Tumour

Stem: A 48-year-old woman presents with a 12 cm breast mass that has grown rapidly over the last 3 months. An ultrasound shows a large, lobulated, hypoechoic mass that appears similar to a fibroadenoma but contains several prominent, elongated, fluid-filled, “cleft-like” spaces.

Question: This appearance, particularly the internal clefts and rapid growth, is most suggestive of:

(A) Phyllodes Tumour (B) Giant Fibroadenoma (C) Invasive Ductal Carcinoma (D) Abscess (E) Haematoma

Correct Answer: (A) Phyllodes Tumour.

Explanation:

  • Why (A) is correct: A phyllodes tumour is a fibroepithelial tumour (like a fibroadenoma) but with a hypercellular stromal component. The key features are large size and rapid growth in a middle-aged woman. The presence of internal cystic, cleft-like spaces is a characteristic imaging feature, representing the “leaf-like” (phyllodes) growth pattern.
  • Why (B) is wrong: A giant fibroadenoma is the main differential, but it is typically solid and does not contain the classic internal clefts.
  • Why (C) is wrong: IDC is typically an infiltrative, spiculated mass, not a large, well-defined, cystic-and-solid mass.
  • Why (D) is wrong: An abscess is a tender, inflammatory collection of pus, not a solid, growing tumour.
  • Why (E) is wrong: A haematoma is a collection of blood, which would be post-traumatic and would evolve over time.

Key Points: Phyllodes Tumour

  • Definition: A rare fibroepithelial tumour; can be benign, borderline, or malignant.
  • Clinical: Large size and rapid growth in a middle-aged woman.
  • Imaging: Appears as a “fibroadenoma on steroids.”
    • Large, well-circumscribed, lobulated.
    • Internal cystic, cleft-like spaces are the characteristic sign.
  • Management: Requires wide local excision (not simple enucleation) due to risk of recurrence.

Question 13: Architectural Distortion

Stem: A 54-y/o woman is recalled from screening for an abnormal mammogram. Tomosynthesis views confirm an area where the breast parenchyma is tethered and drawn in towards a central point. There is no discrete central mass or associated calcifications.

Question: This finding is termed “Architectural Distortion.” Which of the following is least likely to be the cause?

(A) Simple Cyst (B) Invasive Lobular Carcinoma (C) Radial Scar (D) Post-surgical Scar (E) Invasive Ductal Carcinoma

Correct Answer: (A) Simple Cyst.

Explanation:

  • Why (A) is correct: A simple cyst is a fluid-filled, space-occupying lesion. It displaces and compresses adjacent tissue; it does not tether or distort it.
  • Why (B) is wrong: ILC is a classic cause of “stealth” architectural distortion (AD) without a mass.
  • Why (C) is wrong: A radial scar is a classic benign cause of AD (a “great mimic”).
  • Why (D) is wrong: A post-surgical scar (e.g., from a prior lumpectomy) is a very common benign cause of AD.
  • Why (E) is wrong: IDC (especially tubular subtype) can present as spiculated AD.

Key Points: Architectural Distortion (AD)

  • Definition: A focal “pulling” or “tethering” of the normal breast parenchyma without a definite mass.
  • Significance: A highly suspicious finding (BI-RADS 4), as it is often caused by malignancy.
  • Differential Diagnosis:
    • Malignant: ILC (classic), IDC (tubular), DCIS.
    • Benign: Radial Scar, Post-surgical Scar, Fat Necrosis (early).

Question 14: BI-RADS 0

Stem: A 50-year-old woman undergoes her first screening mammogram. The radiologist notes that the breasts are extremely dense, and no focal lesion is seen. The radiologist cannot confidently exclude an underlying mass and recommends a supplementary breast ultrasound.

Question: What is the correct final BI-RADS assessment for this mammogram report?

(A) BI-RADS 0 (B) BI-RADS 1 (C) BI-RADS 2 (D) BI-RADS 3 (E) BI-RADS 4

Correct Answer: (A) BI-RADS 0.

Explanation:

  • Why (A) is correct: BI-RADS 0 means Incomplete Assessment. It is a “holding category” used when the initial imaging (mammogram) is insufficient for a final diagnosis, and additional imaging is required (e.g., supplementary ultrasound for dense breasts, magnification views for calcs, or comparison with prior films).
  • Why (B) is wrong: BI-RADS 1 (Negative) would imply the mammogram was complete and normal (which is not possible to state in extremely dense breasts without US).
  • Why (C) is wrong: BI-RADS 2 (Benign) means a definite benign finding (like a cyst or fibroadenoma) was seen.
  • Why (D) & (E) are wrong: BI-RADS 3 (Probably Benign) and 4 (Suspicious) are used when a specific lesion is identified, which is not the case here.

Key Points: BI-RADS 0

  • Assessment: Incomplete – Need Additional Imaging.
  • Usage:
    • When screening dense breasts, pending a supplementary ultrasound.
    • When an abnormality is seen, pending magnification views.
    • When an abnormality is seen, pending comparison with prior images.
  • Note: It is not a final diagnosis, but a request for more information.

Question 15: Galactocele

Stem: A 30-year-old woman, who is 3 months post-partum and breastfeeding, presents with a new, tender, palpable lump. An ultrasound reveals a well-defined, complex cystic and solid-appearing mass with a distinct “fat-fluid level” that shifts with patient positioning.

Question: What is the most likely diagnosis?

(A) Galactocele (B) Abscess (C) Fibroadenoma (D) Invasive Ductal Carcinoma (E) Simple Cyst

Correct Answer: (A) Galactocele.

Explanation:

  • Why (A) is correct: A galactocele is a milk-filled cyst caused by an obstructed duct. It is the most common benign mass in a lactating or post-partum woman. The key diagnostic feature on ultrasound is the fat-fluid level (the fatty, less-dense milk components “float” on top of the watery component), which is pathognomonic.
  • Why (B) is wrong: An abscess (complication of mastitis) would present with fever/erythema and appear as a complex, thick-walled, hyperaemic collection, but it would not have a fat-fluid level.
  • Why (C) is wrong: A fibroadenoma is a solid, hypoechoic mass.
  • Why (D) is wrong: Carcinoma in pregnancy/lactation is rare but highly aggressive. It presents as an irregular, solid, shadowing mass.
  • Why (E) is wrong: A simple cyst contains simple fluid, not fat and milk.

Key Points: Galactocele

  • Definition: A milk-filled cyst (retention cyst).
  • Clinical: Most common mass in a lactating/post-partum woman.
  • Ultrasound: Appearance is variable (can look simple, complex, or solid).
  • Pathognomonic Sign: A fat-fluid level on ultrasound or mammography.
  • Management: Benign; can be aspirated for symptomatic relief (aspirate is milky).
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