14.2 XCCL, XCCM, Cleavage (CV), and Axillary Tail (AT)

When the Screening CC Is Not Enough

A correctly positioned CC is excellent for medial tissue. The sternum acts as a stop, the medial border is relatively fixed, and many positioning routines deliberately bring the contralateral breast up onto the receptor so the posteromedial breast is not clipped. The cost of that geometry is posterolateral tissue — the tissue most often excluded from the CC. If fibroglandular density or a fat stripe runs off the lateral edge, or if the posterior nipple line on CC is substantially shorter than on MLO because lateral tissue was sacrificed, the CC is incomplete.

ARRT items in this cluster distinguish two clinical moments that look similar on a worklist and are not the same order:

1. Incomplete screening coverage — you add a view during the screening visit so all tissue is on the study before the patient leaves.
2. Diagnostic add-on — a radiologist has already identified a finding (or a possible finding) in that region and requests a targeted extra view.

Facility protocol decides whether an XCCL at screening is automatic or requires a callback. Either way, you must know which extra view recovers which tissue. Grabbing an MLO-lookalike because "it shows more breast" is the wrong answer when the problem is a CC-plane gap.

XCCL — Exaggerated Craniocaudal Lateral

XCCL is a CC-family projection whose field of view is shifted to the posterolateral breast. Start the patient in a true CC, then rotate the torso so the lateral breast — and often a sliver of pectoralis at the lateral chest wall — comes onto the detector. Some units add a small tube angle (about 5°) lateromedially; the beam is still essentially craniocaudal. The nipple will not be centered. It should sit toward the medial side of the image. Include the lateral skin line and as much posterior lateral tissue as the patient can give you.

Use XCCL when:

• The screening CC drops posterolateral tissue (the most common screening add-on in this family).
• A finding is seen only on MLO in the upper-outer quadrant or axillary-tail region and you need a CC-plane image of that same tissue.
• Body habitus (barrel chest, pectus carinatum, prominent ribs) prevents a single CC from covering both medial and lateral extremes; XCCL plus XCCM can replace the CC rather than merely supplement it.

Do not use XCCL to "fix" a short posterior nipple line caused by failing to lift and pull the breast onto the detector. If the whole breast is sitting too far forward, reposition the CC first. An XCCL of an under-pulled breast still misses posterior tissue; it just misses it from a rotated stance.

On the exam, XCCL is the answer to "lateral tissue not on CC." It is not the answer to "axilla not on MLO" (that is AT or a better MLO) and not the answer to "deep medial not on CC" (that is XCCM or cleavage).

XCCM — Exaggerated Craniocaudal Medial

XCCM shifts the CC field to posteromedial tissue. From a CC start, rotate the patient so the sternum and deep medial breast rest on the detector. Bringing the contralateral breast onto the receptor often helps you hold that medial tissue against the chest wall. The nipple drifts toward the lateral side of the image — the opposite of XCCL.

XCCM is less often a screening add-on because a properly positioned CC already privileges medial tissue. It becomes important when:

• A far-medial finding is at the chest wall on MLO and you cannot tell whether it is in the breast or on the chest wall or sternum.
• Pectus excavatum or a prominent sternum excluded medial tissue from the routine CC.
• The radiologist needs a CC-plane image of a medial diagnostic finding that was clipped or superimposed on the original CC.

Pectus pairing: for a depressed or prominent sternum, XCCL and XCCM together can stand in for the CC so medial and lateral extremes are each imaged, while an LM (documented as limited) or LMO may stand in for the MLO. That is a body-habitus strategy, not a license to skip CC on every patient.

Cleavage (CV) / Valley View

The cleavage view (valley view) places both breasts on the detector at once, beam directed superior to inferior, so the deep medial tissue of each breast and the intermammary cleft are in the field. This is the view for a finding that sits in the "valley" — so far medial that a single-breast CC or even XCCM still clips it, or so midline that you cannot tell which breast it belongs to.

CV is not a substitute for XCCM. XCCM is one breast, exaggerated medially. CV is a two-breast, chest-wall–centered image. Label it according to department protocol (CV, or laterality plus CV). Compression is lighter than a standard CC because you are spanning two breasts; the goal is inclusion of deep medial tissue near the chest wall, not maximum optical density of the entire parenchyma. If the order is "medial finding, one breast, still in the CC plane," start with XCCM. If the order is "possible finding in the cleavage, laterality uncertain," CV is the view that answers the question.

Axillary Tail (AT) — Do Not Confuse It With MLO

The axillary tail view images the tail of Spence and the low axilla. It is an oblique projection whose angle is customized to the patient's body habitus so the beam is perpendicular to the axillary tail (superomedial to inferolateral). Drive the detector high into the axilla. The image should isolate the tail: pectoralis and axillary tissue with the tail of the breast — not the full breast from inframammary fold to nipple.

That last point is the discriminator ARRT likes. A well-positioned MLO already includes the axillary tail as part of a whole-breast image: convex pectoralis to nipple level, open IMF, nipple in profile. If the MLO is missing anterior breast or the IMF, the correction is a better MLO, not an AT. If the MLO folded the axilla, or a finding sits in the tail or axilla and is not seen well on MLO or CC, AT is the add-on. An AT that still includes a large slab of central breast is poorly positioned; you have essentially made another MLO and labeled it wrong.

AT also helps when MLO axillary skin folds obscure the tail, for a palpable axillary finding, and for an intramammary or axillary node in the tail that needs a dedicated plane. Lateral tissues that are missing from the CC still belong on XCCL, not AT. AT and XCCL can both show outer-upper anatomy, but they are not interchangeable: XCCL is a CC-plane exaggerated view; AT is an oblique isolated to the tail.

Screening Add-On Versus Diagnostic Request

Screening mammography remains a two-view-per-breast exam. Extra views at the same visit are justified when tissue that should have been on CC or MLO is simply not there. Extra views after interpretation are justified when a finding needs a different plane, less superimposition, or proof of location. Mixing those two indications on the exam — for example, answering "AT" because the radiologist saw a medial CC density — is a content error, not a protocol preference.

Exam traps: labeling AT as MLO; using a 90° ML to recover posterolateral tissue that belongs on XCCL or AT; doing CV when the finding is simply medial in one breast (XCCM is enough); adding XCCL instead of repositioning a CC that was under-pulled rather than laterally incomplete.

Exam Tip: Name the missing edge. Lateral edge of CC → XCCL. Medial edge of CC, one breast → XCCM. Midline valley, laterality unsure → CV. Tail/axilla, not the whole breast → AT. IMF or anterior breast missing on MLO → better MLO, not AT.