The mammary gland is a dynamic organ that undergoes structural and functional changes associated with growth, reproduction, and post-menopausal regression. The postnatal transformations of the epithelium and stromal cells of the mammary gland may contribute to its susceptibility to carcinogenesis. The increased cancer incidence in mammary glands of humans and similarly of rodents in association with their development is believed to be partly explained by proliferative activity together with lesser degree of differentiation, but it is not completely understood how the virgin gland retains its higher susceptibility to carcinogenesis. During its developmental cycle, the mammary gland displays many of the properties associated with breast cancer. An early first full-term pregnancy may have a protective effect. Rodent models are useful for investigating potential breast carcinogens. The purpose of this review is to help recognizing histological appearance of the epithelium and the stroma of the normal mammary gland in rats, and throughout its development in relation to tumorigenic potential.

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The aim of the study was to evaluate the distribution and number of mast cells and eosinophils in rat mammary gland tumours induced by N-Nitroso-N-methylurea. The highest density of mast cells was found in cystic papillary adenocarcinomas of grade II. Eosinophils were detected only in the cystic papillary adenocarcinoma of grades I and II, in non-invasive cribriform adenocarcinoma and comedo-type carcinoma. Mast cell populations were observed perivascularly in the tumour stroma, in the host tumour interface, as well as in necrotic areas of neoplasms. Mast cells were observed to be intact according to their morphological changes, collectively referred to as degranulation. The obtained results indicate that mast cells and eosinophils play an important role in tumour micro-environment formation. The increased density of these cells in experimentally-induced rat mammary gland tumours suggests a poor prognosis in these cancers. Our results also confirmed that rat mammary gland tumours are good models for the study of breast cancers.

The purpose of this study was to demonstrate the normal and variant anatomy of extraorbital and intraorbital venous drainage together with retroorbital communication, and determine the lymphatic drainage from the superficial orbital region with a potential outlet of lymphatic vessel into the venous bloodstream. The study of the venous system was carried out on 32 Wistar rats by using corrosion casts methods and radiography, while the lymphatic system was studied in 12 Wistar rats following ink injection. Superficially, orbital veins are connected with extraorbital veins running through angular vein of the eye and the superficial temporal vein, and via the pterygoid plexus with the maxillary vein, which provide readily accessible communication routes in the spread of infection. The extent of intraorbital and periorbital venous drainage was ensured by the dorsal and ventral external ophthalmic vein through the infraorbital vein, which together formed the principal part of the ophthalmic plexus. Venous drainage of the eyeball was carried out mainly by the vortex veins, ciliary veins and internal ophthalmic vein. The highest variability, first presented by differences in structural arrangement and formation of anastomoses, was observed within the ventral external ophthalmic vein (22 cases) and the medial vortex vein (10 cases). Four vortex veins, one vein in each quadrant of the eye, were observed in rats. The vortex vein located on the ventral side of the eyeball was occasionally found as two veins (in four cases) in the present study. The lymphatic vessel from the lower eyelid entered into the mandibular lymph centre, and from the upper eyelid entered into the superficial cervical lymph centre, but both drained into the deep cranial cervical lymph node. The direct entry of lymph entering the veins without passing through lymph nodes was not observed.