16.1 Chest Wall Variations, Kyphosis/Lordosis, Protruding Abdomen, and Extreme Breast Size
Key Takeaways
- Pectus excavatum hides medial tissue on the CC; recover it with a cleavage view or XCCM rather than harder compression.
- Kyphosis often needs a from-below CC and an LMO instead of a forced textbook CC/MLO pair.
- A protruding abdomen is managed by standing the patient back, leaning the thorax in, and reducing MLO angulation so the inframammary fold stays on the receptor.
- Extremely large breasts: choose paddle size first, then mosaic or tile with at least 2.5 cm of overlap and labeled segments.
- Extremely small breasts need the smallest available or spot paddle so the breast cannot slide out during compression.
Why chest-wall and habitus variance is a Procedures item
The ARRT Mammography content specifications effective September 1, 2025 list Patient Variance under Procedures 2.B. The first cluster is mechanical: chest wall variations (pectus excavatum, pectus carinatum), kyphotic/lordotic patients, a protruding abdomen, and extremely large or small breasts, including mosaic, tiling, and paddle selection. The exam is not asking you to name the deformity. It is asking whether you still put posterior tissue, medial tissue, the nipple, and the inframammary fold (IMF) on the image after the chest or the breast refuses a textbook pose.
Quick Answer: Change the angle, the paddle, or the number of images before you accept a limited study. Extra compression does not lift tissue out of a sternal well or around a hunched thorax.
Standard craniocaudal (CC) and mediolateral oblique (MLO) positioning assumes a mobile breast on a relatively flat anterior chest. Real screening rooms are full of sunken sternums, keel-shaped chests, flexed thoracic spines, and breasts that either overflow the largest paddle or underfill the smallest one. Your job is to adapt C-arm angle, receptor height, patient lean, and field coverage so the study remains diagnostic.
Pectus excavatum (funnel chest)
Pectus excavatum is a depressed sternum. The medial chest wall drops away from the image receptor, so the CC view characteristically loses medial tissue. The ribs may sit more anterior than the sternum, which makes the patient feel as if she is being rolled off the detector.
On CC, capture central and lateral tissue on the first image. Then recover the medial remnant with a cleavage view (CV) or an exaggerated craniocaudal medial (XCCM). Place the receptor at a neutral IMF rather than forcing maximum elevation; a slightly lower receptor lets the patient lean in so medial tissue reaches the field. A spot-compression paddle can isolate a small medial island without the full paddle colliding with the contralateral chest.
On MLO, a steep angle that works on a flat chest may exclude medial-posterior tissue. If the sternum is so recessed that the standard MLO cannot bring the medial breast onto the receptor, a lateromedial oblique (LMO) — the reverse oblique — often includes more tissue because the receptor now faces the depressed wall. Document a limited study if posterior tissue remains incomplete after the adapted views.
Pectus carinatum (pigeon chest)
Pectus carinatum is the opposite deformity: the sternum protrudes. Medial tissue is usually easy to include. Lateral tissue is the usual miss because the breast is draped around a keel.
Obtain a medial and central CC, then an exaggerated craniocaudal lateral (XCCL) for the outer breast. The LMO can reduce the collision between a protruding sternum and the receptor edge on the oblique. Do not try to flatten the chest wall with aggressive compression. You will produce pain, motion, and still miss the lateral tail.
Kyphosis and lordosis
A kyphotic patient has an exaggerated thoracic curve — hunched back, rounded shoulders, limited neck extension. She often cannot rest the superior breast on a standard CC receptor. Replace the CC with a from-below (FB) projection: rotate the C-arm so the receptor sits at the superior breast and compression comes from inferiorly. If FB is not feasible, piece the CC plane together with XCCL and XCCM. Replace the MLO with an LMO. An LM can stand in only as a documented limited study, not as a silent substitute for a complete oblique.
A lordotic patient has an exaggerated lumbar curve and often an anterior pelvic tilt. The abdomen and lower thorax push her off the unit. Treat this like a protruding abdomen: stand her slightly away from the receptor, have her bend at the waist so the breast — not the belly — meets the detector, and reduce MLO angulation (often toward 30–40°) so the receptor stays parallel to the pectoralis without the abdomen lifting the inferior breast off the field. The IMF is the first structure lost when lumbar lordosis occupies the inferior receptor.
Never force a kyphotic patient into a textbook CC. The correct exam answer is the adapted view, not a repeat of a failed standard pose.
Protruding abdomen
A prominent abdomen collides with the receptor on both CC and MLO. Start with the patient standing a step back, then lean the thorax forward so the breast reaches the detector while the abdomen stays clear. On MLO, lower the tube angle to support the anterior breast against gravity and to keep the belly from occupying the inferior field. Watch the IMF on every image; if it is off the receptor, the lean or the angle is still wrong.
Thin, long-waisted patients often need steeper MLO angulation (toward 50–60°) because the pectoralis is steep. Heavy or short-waisted patients, and those with a protruding abdomen, usually need shallower angulation. Match the receptor to the muscle, not to a single remembered number.
Extremely large and extremely small breasts
Paddle selection comes before extra images. Match paddle size to the breast, not to habit or to whichever paddle is already on the unit. A paddle that is too large lets a small breast slide. A paddle that is too small on a large breast under-compresses the anterior tissue while the posterior mound holds the paddle up.
Extremely small breasts
Use the smallest available paddle or a spot or half paddle. Support the breast from behind so your hand is not in the field when the paddle seats. The FB view can help when a short breast, or chest hair on a male or very small female breast, will not stay on a standard CC receptor. Avoid burying a tiny breast under a thick slab of pectoralis on the MLO; too much muscle under the paddle steals compression from the anterior tissue that actually needs it.
Extremely large breasts: mosaic, tiling, and overlap
If the breast still does not fit after the largest appropriate paddle is chosen, mosaic (also called tiling or sectional imaging). Overlap adjacent sections by at least 2.5 cm (1 inch) so a lesion at a seam is not excluded. Label every image by segment — CC lateral and CC medial; MLO superior and MLO inferior; or an anterior CC when the posterior mound has already been captured.
On CC, capturing the lateral breast first, then a CV for both medial breasts, can reduce extra exposures if the interpreting radiologist agrees that the medial tissue is adequately shown. On MLO, a shallower angle (often near 40°) supports a heavy breast. A prominent axillary fat pad is a reason to tile rather than to over-compress the posterior axilla at the expense of the anterior breast. Flex paddles can improve anterior compression when the posterior breast is much thicker than the anterior breast — a common large-breast problem.
Do not lean a large-breasted patient so far over the receptor that the inferior breast falls off both CC and MLO. If you must lean, re-check the IMF before you expose.
Variance to CC and MLO adjustments
| Variance | CC adjustment | MLO adjustment |
|---|---|---|
| Pectus excavatum | Neutral IMF; add CV or XCCM for medial tissue | Consider LMO if medial-posterior tissue is excluded |
| Pectus carinatum | Medial/central CC plus XCCL for lateral tissue | LMO often clears the protruding sternum |
| Kyphosis | FB, or XCCL/XCCM if FB is not possible | LMO; LM only as a documented limited substitute |
| Lordosis / protruding abdomen | Stand back, lean the thorax in, protect the IMF | Reduce angulation; keep the abdomen off the receptor |
| Extremely large breast | Largest appropriate paddle first; mosaic with ≥2.5 cm overlap | Shallower angle; tile if an axillary fat pad blocks anterior compression |
| Extremely small breast | Smallest or spot paddle; prevent slip | Small paddle; do not bury the breast under excess pectoralis |
Exam traps
The usual distractor is more compression. Force does not replace missing geometry. A second trap is unlabeled mosaics — tiled images without anterior/posterior or medial/lateral labels are not a complete exam. A third is treating FB or LMO as wrong because they are not the two standard screening views. Under 2.B they are the correct variance views when the standard pair cannot include the tissue. A fourth is using a large receptor on a wide, short-waisted CC and then forgetting to drop to a smaller paddle on MLO so the pectoralis is not stretched and the anterior breast is not under-compressed.
A patient with pectus excavatum has a technically adequate lateral CC, but the radiologist cannot see the medial breast. Which adaptation best recovers the missing tissue?
A kyphotic patient cannot extend enough to rest the superior breast on the CC receptor. Which substitution is the best first CC replacement?
You must mosaic an extremely large breast because even the largest appropriate paddle cannot include the entire CC field. What overlap and labeling rule keeps the exam diagnostic?