correlations between gross and microscopic lesions in carcinogenic studies in mice microscopic diagnoses of a number of spontaneous and induced neoplasms in mice were correlated with the gross findings of the ed01 and a number of other carcinogenic studies conducted at nctr to determine the value of detailed histopathologic examinations in bioassay testing the results indicated that for organs such as thymus lung adrenal harderian gland and urinary bladder 50 or more of the neoplastic lesions would be missed if at least one histological section were not examined from each organ for organs such as the liver and mammary gland a single tissue section did not greatly improve the ability to detect neoplastic lesions beyond that afforded by a thorough necropsy examination