As per CPT assistant article Fall 1994 page 18
CPT code 11100 describes the biopsy of skin, subcutaneous tissue and/or mucous membrane (including simple closure), unless otherwise listed. Since there are specific breast biopsy codes, this more generic biopsy code would not be reported for breast biopsies. The "unless otherwise listed" phrase indicates that you should look for a more specific code under the anatomic location of the site from which the physician is taking the biopsy. If there is not a more specific code in that section, then you can "default" to this code. However, in the case of breast biopsies, there are specific codes and this generic code (11100) would not be reported for a breast biopsy.
11100Biopsy of skin, subcutaneous tissue and/or mucous membrane (including simple closure), unless otherwise listed (separate procedure); single lesion
11101each separate/additional lesion
Breast falls under integumentary section only ,therefore the preference is to 19101.