Gross necropsy
(11) Gross necropsy. (i) All animals must be subjected to a full gross necropsy which includes examination of the external surface of the body, all orifices, and the cranial, thoracic and abdominal cavities and their contents. (ii) The liver, kidneys, adrenals, testes, epididymides, ovaries, uterus, thymus, spleen, brain, and heart must be trimmed and weighed wet, as soon as possible after dissection. (iii) The following organs and tissues, or representative samples thereof, should be preserved in a suitable medium for possible future histopathological examination: (A) Digestive systemsalivary glands, esophagus, stomach, duodenum, jejunum, ileum, cecum, colon, rectum, liver, pancreas, gallbladder (when present). (B) Nervous systembrain (including sections of medulla/pons, cerebellum and cerebrum), pituitary, peripheral nerve (sciatic or tibial, preferably in close proximity to the muscle), spinal cord (three levels: cervical, mid-thoracic and lumbar), eyes (retina, optic nerve). (C) Glandular systemadrenals, parathyroid, thyroid. (D) Respiratory systemtrachea, lungs, pharynx, larynx, nose. (E) Cardiovascular/hemopoietic systemaorta, heart, bone marrow (and/or fresh aspirate), lymph nodes (preferably one lymph node covering the route of administration and another one distant from the route of administration to cover systemic effects), spleen, thymus. (F) Urogenital systemkidneys, urinary bladder, prostate, testes, epididymides, seminal vesicle(s), uterus, ovaries, female mammary gland. (G) Othersall gross lesions and masses, skin. (12) Histopathology. (i) The following histopathology must be performed: (A) Full histopathology on the organs and tissues, listed in paragraph (e)(11)(iii) of this section, of all rodents in the control and high dose groups, and all rodents that died or were sacrificed during the study. (B) All gross lesions in all animals. (C) Target tissues in all animals. (D) When a satellite group is used, histopathology should be performed on tissues and organs identified as showing effects in the treated groups. (ii) If excessive early deaths or other problems occur in the high dose group compromising the significance of the data, the next dose level should be examined for complete histopathology. (iii) An attempt should be made to correlate gross observations with microscopic findings. (iv) Tissues and organs designated for microscopic examination should be fixed in 10% buffered formalin or a recognized suitable fixative as soon as necropsy is performed and no less than 48 hours prior to trimming.