Mitosis counting in seminoma: an exercise of questionable significance.

Two pathologists reviewed and classified 45 cases of testicular seminoma, evaluating each case for multiple histologic variables, including mitotic rate. In addition to recording the mitotic count for each of thirty 0.1963-mm2 high-power fields, the investigators recorded the distribution of mitotic counts in many non-spermatocytic seminomas. Statistically significant differences for mitotic rate in the nonspermatocytic tumors were noted between the observers; one observer found a mean mitotic rate of 1.815/high-power field for 43 such tumors, whereas the other noted a mean mitotic rate of 1.388/high-power field (p = 0.001). These differences led to disagreement on the classification of 3 tumors. Of the 4 cases considered to be high-mitotic-rate seminomas by one or both observers, all patients had presented with stage I disease. Three of the patients were followed up for 23, 55, and 56 months, and all were free of disease; the fourth was lost to follow-up. The patient with the highest mitotic rate was free of disease at 55 months of follow-up. On the basis of our findings we question the value of the designation high-mitotic-rate seminoma. Analysis of the distribution of mitotic counts within the tumors revealed them to be Poisson distributed. With these data and other empirically derived data, it was possible to estimate the probability of misclassification of seminoma based on mitotic rate, the diagnostic mitotic rate threshold, and the number of fields counted for mitoses. Similar analysis might be valuable for other tumors, particularly those of smooth muscle origin, in which mitotic rate is of diagnostic or prognostic value.

[1]  P S Ellis,et al.  Mitosis counting--a need for reappraisal. , 1981, Human pathology.

[2]  R. Kempson,et al.  Mitosis counting—II , 1976 .

[3]  R. Huben,et al.  Seminoma at roswell park, 1970 to 1979. An analysis of treatment failures , 1984, Cancer.

[4]  J. Maier,et al.  Seminoma of the testis: analysis of treatment success and failure. , 1968, The American journal of roentgenology, radium therapy, and nuclear medicine.

[5]  S. Silverberg,et al.  Reproducibility of the mitosis count in the histologic diagnosis of smooth muscle tumors of the uterus. , 1976, Human pathology.

[6]  J. Maier,et al.  Treatment and prognosis in seminoma of the testis. , 1968, The Journal of urology.

[7]  J. Clements,et al.  Anaplastic seminoma. An analysis of 77 patients , 1979, Cancer.

[8]  J. Maier,et al.  Radiation therapy in malignant testis tumors. Part I: Seminoma; Part II: Carcinoma , 1973 .

[9]  F. Mostofi,et al.  Testicular tumors. Epidemiologic, etiologic, and pathologic features , 1973 .

[10]  Henry J. Norris,et al.  Mitosis counting—III , 1976 .

[11]  William Feller,et al.  An Introduction to Probability Theory and Its Applications , 1951 .

[12]  A. Hartmann,et al.  Analysis of proliferative compartments in human tumors. II. Seminoma , 1985, Cancer.

[13]  F. Mostofi,et al.  Pathology of Germ Cell Tumors of Testis , 1980, Cancer.

[14]  R. Scully.  Mitosis counting—I , 1976 .

[15]  V. Saxena.  Seminoma of the testis. , 1973, The American journal of roentgenology, radium therapy, and nuclear medicine.

[16]  J. Bartko.  The Intraclass Correlation Coefficient as a Measure of Reliability , 1966, Psychological reports.

[17]  J. Herman,et al.  Seminoma of the testis: results of treatment and patterns of failure after radiation therapy. , 1982, International journal of radiation oncology, biology, physics.