One hundred fifty-four patients with brain tumors of various types were given an intravenous infusion of the thymidine analogue bromodeoxyuridine (BUdR), 200 mg/m2, at the time of surgery but before biopsy of the tumor to label S-phase cells. Excised tumor specimens were fixed, sectioned, and stained by immunoperoxidase methods to detect BUdR. The labelling index (LI), or percentage of BUdR-labelled cells, was calculated for each tumor specimen. The LIs of glioblastomas, medulloblastomas, and most highly anaplastic astrocytomas were 5% to 20%. The majority of moderately anaplastic astrocytomas showed LIs of less than 1%, but 30% of them had LIs similar to those of highly malignant gliomas. Most pituitary adenomas and neurinomas showed LIs of less than 1%. Nonmalignant meningiomas had LIs of less than 1%, whereas malignant meningiomas had LIs higher than 2.7%. This is an important observation, because malignant meningiomas are not well-defined histopathologically and their growth rate and rate of recurrence cannot be predicted by current diagnostic procedures. By estimating the proliferative potential of individual tumors more precisely, the BUdR LI supplements histopathological diagnosis, allowing a more accurate estimate of prognosis and facilitating the design of treatment regimens for individual patients.

A 65-year-old man with a history of exposure to industrial solvents developed a primary cerebral angiosarcoma in the left posterior parieto-occipital lobe. The tumor had features typical of angiosarcoma on light and electron microscopy, immunohistochemical evidence of factor VIII-related antigen produced in tumor cells, and a high labeling index with bromodeoxyuridine. The relationship of angiosarcoma to toxins and viruses is discussed.

The proliferative potential of low-grade astrocytomas was estimated in 47 patients. Each patient received an intravenous infusion of bromodeoxyuridine (BUdR), 150 to 200 mg/sq m, at the time of craniotomy to label cells in deoxyribonucleic acid (DNA) synthesis; the percentage of S-phase cells, or BUdR labeling index (LI), of each tumor was determined immunohistochemically. In 29 patients (60%), the tumors had BUdR LI's of less than 1%, indicating a slow growth rate; only three (10%) of these patients died of recurrent tumor during a follow-up period of up to 3 1/2 years. In contrast, of the 18 patients (40%) whose tumors had BUdR LI's of 1% or more, 12 (67%) had a recurrence and nine died during the same follow-up period. These results show that the proliferative potential, as reflected by the BUdR LI, is an important prognostic factor that separates low-grade astrocytomas into two groups and provides a more scientific rationale for selecting treatment for individual patients.

One hundred fifty-two intracranial gliomas of various types were reviewed in order to correlate the histopathological features with the proliferative potential of each tumor as reflected by the bromodeoxyuridine (BUdR) labeling index (LI). Patients undergoing surgical removal of gliomas were given a 30-minute intravenous infusion of BUdR (150 to 200 mg/sq m) to label S-phase tumor cells. The tumor specimens were stained immunohistochemically for BUdR and processed for routine histopathological diagnosis. The BUdR LI was calculated as the percentage of labeled cells among cells analyzed. Twenty-seven histological features in three categories (degenerative, vascular, and cellular changes) were considered. A significantly higher BUdR LI (p less than 0.05) was found in tumors with necrosis than in those without this feature; tumors with both coagulative and liquefactive necrosis had the highest BUdR LI (p less than 0.05). Increased vascularity was also associated with a higher BUdR LI (p less than 0.05). Although tumors with abnormal mitotic figures had a significantly higher BUdR LI than those without, the number of mitoses did not correlate with a higher BUdR LI. These results suggest that the number of mitoses is not a good indicator of tumor growth rate. Necrosis and increased vascularity should be heavily weighted in predicting the proliferative potential of individual gliomas.

Sixteen patients with brain tumors were given a 30- to 60-minute intravenous infusion of bromodeoxyuridine (BUdR), 200 mg/sq m. Grossly viable fragments were taken from the biopsied tumor specimens and divided into two portions. One portion was dissociated into single cells, stained both with fluorescein isothiocyanate (FITC) using anti-BUdR monoclonal antibody as the first antibody and with propidium iodide (for deoxyribonucleic acid), and analyzed by flow cytometry (FCM). The labeling index (LI) was calculated as the number of FITC-labeled cells expressed as a percentage of the total number of cells analyzed. The other portion was fixed in 70% ethanol, embedded in paraffin, sectioned, and stained with immunoperoxidase using anti-BUdR monoclonal antibody as the first antibody. The LI of these tissue sections was calculated in two ways: from selected areas in which the labeled cells were evenly distributed and from the entire tissue section. The LI's obtained by FCM correlated closely with those from the entire tissue sections (r = 0.99, p less than 0.000001) and were usually lower than LI's from selected areas of tissue sections. The LI's determined by FCM also correlated well with the LI's from selected areas of tissue sections (r = 0.82, p less than 0.00012), despite the difference in values between them. Thus, the FCM-derived LI and the tissue LI can both provide useful information for predicting the biological malignancy of individual tumors and for designing treatment regimens for individual patients with brain tumors; however, different standards should be used to interpret the LI's obtained by these two methods.