Morphology of Spontaneous Brain Tumors in the Rat

Abstract

Abstract. In lifespan studies of 2,242 rats of three strains, 32 neoplasms were identified in brain, meninges and pineal gland. They were astrocytoma ( 16 Wistar, three Sprague-Dawley), ependymoma (four Osborne-Mendel), meningioma (two Osborne-Mendel, one Wistar), pinealoma (two Osborne-Mendel), reticulosis (two Wistar), oligodendroglioma (one Wistar), and gliomatosis (one Wistar).There has been a renaissance of interest in brain tumors of laboratory animals with the realization that exogenous and, perhaps, environmental factors may influence their induction and growth [ I , 81. Spontaneous brain tumors in the rat are infrequently reported [ 1 I], often only as case reports or merely tabulated along with the incidence of other tumors. The largest study with morphologic descriptions involved 41,000 Sprague-Dawley rats with 38 central nervous system tumors for an incidence of only 0.09% [9]. Another study of 7,803 Sprague-Dawley rats described 34 brain or meningeal tumors, an incidence of 0.44% [4]. In other reports, three brain tumors were described in 1,100 Wistar rats [2], and an unusual type of granular cell tumor of the central nervous system was described in 12 aged BN/BI rats [6]. Tabulations of brain tumors in additional reports also indicate a low spontaneous incidence of brain tumors in rats [3, 5 , 10, 12, 14-16]. Our data suggest that the incidence of brain tumors in aged rats is considerably higher than previously reported. Materials and MethodsThree-to 5-month-old healthy female Osborne-Mendel rats were obtained from the Charles River Breeding Colony (Wilmington, Mass.); female Sprague-Dawley and male and female Wistar rats were purchased from Hilltop Laboratory (Chatsworth, Calif.). The rats were in our laboratory for the remainder of their life span in climate-controlled rooms with filtered air kept at 22 k 1" C and 50 f 20% relative humidity. The Osborne-Mendel and Sprague-Dawley rats were housed in pairs in wire-bottom cages placed in automatically flushing racks equipped with automatic waterers. Wistar rats were housed four to five in a 20-centimeter deep plastic cage with 390 cm2 floor space with Sanicel (Paxton Processing, Paxton, Ill.) bedding and water bottles attached to cages. All rats were fed Wayne Lab-Blox (Allied Mills, Chicago, Ill.) laboratory rat diet with 4% crude fat content. The Osborne-Mendel and Sprague-Dawley rats were on a n experiment with cigarette smoke condensate-beeswax pellets implanted into the lung. The Wistar rats were on low-level radiation studies with inhaled or intravenously 318

Spontaneous Brain and Spinal Cord/Nerve Neoplasms in Aged Sprague-Dawley Rats

“…In the past 15 yr, there have been a few more reports on spontaneous brain neoplasms in rats where the incidences varied broadly from < 1 to 10-12%, with incidence in males greater than in females. Brain neoplasms in rats are clearly not as rare as first reported but generally have an incidence between 0.5 and 3.0%, depending on the rat strain and sex being reported (3,7,(9)(10)(11)(12). There were no histological variants of astrocytoma in this series consistent with spontaneous &dquo;glioblastoma multiforme,&dquo; as reported elsewhere (15).…”

“…The spontaneous incidence of brain neoplasms among laboratory rats found in the pre-1976 literature was < 1 % (9). Since then, a few more reports have established that the incidence in laboratory rats varies but ranges from < 1 to about 3% (3,(5)(6)(7)12 (Fig. 3a, b).…”

Ependymoma in a Rat

“…Tumor cells proliferated in the dilated ventri- No metastatic lesion were detected in the other than the brain. The findings in the present case are very similar to those of ependymoma described by previous workers [3][4][5][6].…”

“…One of them is glioma often detected in the cerebral hemispheres, most of which are astrocytoma, and ependymoma is less frequent [3][4][5].…”

Incidence of Brain Tumours in Rats Exposed to an Aerosol of239PuO2

“…0%, while Wistar males exhibit a significantly higher incidence (Goodman et al . 1980, Lang 1988, Dagle et al . 1979, Mawdesley-Thomas and Newman 1974, Fitzgerald et al .…”