Skin, transverse and longitudinal cutting direction.

Skin, inguinal region: transverse and longitudinal cutting direction.

Skin and mammary gland (M), section transverse to the direction of the hair flow.

Skin, longitudinal section in the direction of the hair flow.

The mammary gland is a paired organ. Due to the diffuse distribution of mammary gland tissue it is of no concern whether one or both sides are in the section. The inguinal region is the recommended area for harvesting mammary gland. Sections of mammary gland should be taken with associated nipple and skin. The result of histotechnique may be improved by shaving the skin at necropsy or removing the hair with scissors at trimming. Orientation of a shaved skin specimen is possible by the nipples in female animals. In male animals, the inguinal region is also preferred to examine skin and mammary gland tissue. The section will be embedded on the cut edge so that it reveals skin, subcutis and mammary gland close to the nipple. In the longitudinal section, the hair follicles will be visible in full length.

Relevant differences between rats and mice
Rats have 6 pairs of mammary glands while mice have only 5 pairs. This difference is not of practical importance since mammary tissue is abundant in the inguinal region of both species. In females, the mammary tissue extends from the salivary gland region to the base of the tail.

See also:
      Introduction

	Boorman GA, Wilson JT, Van Zwieten MJ, et al. (1990) Mammary gland. In: Boorman GA, Eustis SL, Elwell MR, Montgomery CA, Jr, MacKenzie WF (eds) Pathology of the Fischer rat. Reference and atlas. Academic Press, San Diego New York London, pp 43–61
	Deerberg F, Knüp F, Rehm S (1986) Spontaneous epithelial tumors of the skin in Han:WIST- and DA/Han rats. Z Versuchstierkd 28: 45–57
	Elwell MR, Stedman MA, Kovatch RM (1990) Skin and subcutis. In: Boorman GA, Eustis SL, Elwell MR, Montgomery CA, Jr, MacKenzie WF (eds) Pathology of the Fischer rat. Reference and atlas. Academic Press, San Diego New York London, pp 261–277
	Kovatch R (1990) Neoplasm of the integument. In: Stinson SF, Schüller HM, Reznik GK (eds) Atlas of tumor pathology of the Fischer rat. CRC Press, Boca Raton, pp 19–32
	Kovatch R (1990) Neoplasms of the mammary gland. In: Stinson SF, Schüller HM, Reznik GK (eds) Atlas of tumor pathology of the Fischer rat. CRC Press, Boca Raton, pp 473–484
	Militzer K, Hirche H, Moog E (1990) The ontogenesis of skin and organ characteristics in the Syrian golden hamster. 1. Skin compartments and subcutaneous adipocytes. Exp Pathol 40: 77–93
	Russo IH, Tewari M, Russo J (1989) Morphology and development of the rat mammary gland. In: Jones TC, Mohr U, Hunt RD (eds) Monographs on pathology of laboratory animals. Integument and mammary glands. Springer, Berlin Heidelberg New York Tokyo, pp 233–252

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Reference: Ruehl-Fehlert C, Kittel B, Morawietz G, et al. (2003) Revised guides for organ sampling and trimming in rats and mice – Part 1. A joint publication of the RITA and NACAD groups. Exp Toxic Pathol 55: 91–106