Dissection of Mouse Mammary Tumors

Before bringing the mouse up from the animal house, be sure that you have prepared:

camera and appropriate lens, film, light box, etc.diaper on which to photograph the mouse

pins for dissection

70% EtOH (in a beaker to sterilize instruments)

curved-blade scissors

scalpel blades and holder

styrofoam box top or something like it to rest the mouse on during dissection

Be sure, also, that formalin and liquid nitrogen are available, as well as the plastic hinged cassettes to put specimens in for formalin fixation; cardboard pieces cut to appropriate size to put tissue samples on inside cassettes; and the orange cryovials for freezing tissue in liquid nitrogen.



1. Print out a clean copy of the Mouse Template for recording data, verify ms ear #, Label cassettes, slides and Liquid Nitrogen tubes.

2. Record mouse data (defined on template) eg mouse identifier, line #, ms # DOB, DOD

3. Define where samples will be stored in Liq Nitrogen according to chart on wall

4. Kill the mouse. (use only a 1-inch cube of dry ice-protect from freezing).

Cut the tail (save for genotyping)

5. Cut through just the skin (not the body wall) on the ventral side (keep scissor tips up); pull skin away from mouse body and pin down to expose mammary glands.

6. Note and record pregnancy/breeding status of mouse- take uterine horn into PBS and dissect embryos later.

7. Record position and appearance of tumors (photograph if desired)

8. Record appearance of salivary glands as well as uninvolved mammary glands (e.g., Are they very vascularized? Is there hyperbranching?)

9. Process specimens as follows:

For mice with tumors: half of each tumor in liquid nitrogen and half in formalin (slice thinly to permit the fixative to penetrate the tissue); Place an opposite control mammary gland in liquid nitrogen and another in formalin - press cardboard onto the gland and dissect underneath with the scalpel blade. Place cardboard into labeled cassette.

For other mice: MG4 for whole mount; MG9 for formalin; Freeze the rest in Liq Nit

10. Uninvolved mammary glands that are not needed as tumor controls may be frozen in liquid nitrogen or spread on glass slides to be processed as whole mounts.

11. Note any other irregularities (e.g., lungs, liver, spleen, etc.) and take any other desired tissues for freezing or formalin fixation.

12. ANNOTATE Liquid Nitrogen Book and put away samples