Computer-aided analyses in diagnostic histopathology

Immunocytochemical detection of ornithine decarboxylase (ODC) in paraffin-embedded tissues as a possible prognostic indicator for oral lesions

Intracellular levels of ornithine decarboxylase (ODC) are raised following mitogenic stimulus and in neoplasia. Because lesions of the oral cavity are often difficult to assess histologically, we have determined the value of immunocytochemical detection of ODC as a prognostic indicator in 74 routinely fixed and paraffin-embedded oral biopsies using peroxidase-antiperoxidase and immunogold-silver staining. The latter proved more sensitive, yielding positive reactions in 32 of 43 oral carcinomas (11/14 well differentiated, 16/21 moderately differentiated and 3/5 poorly differentiated) and 7/11 potentially malignant lesions, compared with 19/45 carcinomas and 1/15 potentially malignant lesions, by peroxidase anti-peroxidase. Hyperplastic lesions (n = 7) and normal non-keratinized buccal mucosa (n = 7) were all negative. Follow-up was possible in 13 of the carcinoma patients. Of 7 positive ODC reactions but clinically node-free at biopsy, 2 died and 2 had recurrences within 3 years, whereas all of 6 with no immunoreactivity were symptom-free after 3-5 years. Immunostaining for ODC may be helpful for the prognostic assessment of routinely processed oral lesions and in choosing treatment.

Observer variability in the histologic assessment of oral premalignant lesions

Histopathologic examination of oral leukoplakias has a major impact on the assessment of prognosis and treatment planning. We investigated the extent of agreement in grading epithelial dysplasia between pathologists with the same or different educational backgrounds. Two general pathologists and two oral pathologists were each given 100 sections of oral leukoplakia to grade from no dysplasia to carcinoma in-situ. The interobserver agreement rates were in the range of 49% to 69%. The calculated kappa values were in the range of 27% to 45%, showing poor to moderate agreement between the pathologists. When comparing the kappa values between the two pairs of pathologists with the same education, these values did not diverge from the general level of kappa values, indicating that the interobserver variability was due to individual differences rather than to educational background.

Measuring repeatability and validity of histological diagnosis--a brief review with some practical examples

Evaluation of histological diagnosis requires an index of agreement (to measure repeatability and validity) together with a method of assessing bias. Cohen's kappa statistic appears to be the most suitable tool for measuring levels of agreement, which if unsatisfactory may be caused by bias. Further study of bias is possible by examining levels of agreement for each diagnostic category or by searching for categories of disagreement in which more observations occur than would be expected by chance alone. This article gives reasons for choosing the kappa statistic, with examples illustrating its calculation and the investigation of bias.

Correlative clinico-pathological evaluation of oral premalignancy

In 1972, the World Health Organization's "Meeting of Investigators on the Histological Definitions in Precancerous Lesions" defined a precancerous lesion as a "morphologically altered tissue in which cancer is more likely to occur than in its apparently normal counter part" (Pindborg 1980). There are two generally accepted precancerous lesions in the oral cavity, leukoplakia and erythroplakia (Pindborg 1980). Leukoplakia is currently defined as "a white patch or plaque that cannot be characterized clinically or pathologically as any other disease" (WHO 1978). This definition has no histological connotation and is used in a strictly clinical sense (Pindborg 1980, Banoczy 1977). Erythroplakia is defined as a "bright red velvety plaque which cannot be characterized clinically or pathologically as being due to any other condition" (Pindborg 1980).

Quality control in histopathology and diagnostic cytology

The need for quality control in diagnostic histopathology and cytology is analysed together with a discussion of previously reported experience in this field. The philosophical and mathematical inferences of this type of exercise are debated also in relationship to personally observed experiences in respect of uterine cervical cytology and histology. The desirability of methods of monitoring of diagnostic quality and of obtaining quality improvement are emphasized and suggestions made regarding the techniques most suited to these objectives.