The lesion shifted up on the mediolateral view (not shown), indicating the lesion was in the medial breast. Despite considerable effort by experienced breast imagers, the lesion could not be localized at US. Stereotactic biopsy was thought difficult due to far posterior location.
http://radiology.rsna.org/content/248/1/61.figures-only

Caudal

Of, at, or near the tail or hind parts; posterior: the caudal fin of a fish.
b. Situated beneath or on the underside; inferior.
2. Similar to a tail in form or function.
Adjective
Zool at or near the tail or back part of an animal's body [Latin cauda tail]
Adv.1.caudal - toward the posterior end of the body
caudally
Adv.1.caudally - toward the posterior end of the body

http://www.thefreedictionary.com/caudal

Mammographic imaging: a practical guide - Google Books Result
by Valerie Andolina, Shelly Lillé, Kathleen M ... - 2001 - Medical - 498 pages
If the image receptor is too high (even if the image receptor is placed just posterior to the axilla), posterior and lateral tissue will be lost (D). ...
books.google.com.mx/books?isbn=0781716969...

Fundamentals of mammography - Google Books Result
by Linda Lee, Verdi Stickland, A. Robin M. Wilson ... - 2003 - Medical - 171 pages
Ensure that the corner of the support table lies in the axilla, immediately anterior to the posterior axillary fold. Figure 5.21 Figure 5.22 Figure 5.23 ...
books.google.com.mx/books?isbn=0443071144...

in upper inner quadrant in 59-year-old woman, which was probably not marked by computer-aided detection (CAD) device because of far posterior location. Spot magnification view with skin marker over corresponding lesion seen with sonography. "

https://bmir-gforge.stanford.edu/gf/project/ontrez/scmsvn/?a...