Benign giant-cell tumor of bone with pulmonary metastases: clinical findings and radiologic appearance of metastases in 13 cases.

Tumors that metastasize are considered "malignant" by definition. However, benign giant-cell tumor of bone is an exception because of the potential for histologically benign pulmonary metastases, a fact seldom emphasized in the radiologic literature. We therefore report our experience with 13 cases of pulmonary metastasis among 475 patients (prevalence, 3%) in whom benign giant-cell tumor of bone was diagnosed before 1990 at our institution. Five (38%) of the 13 primary bone tumors were located in the distal radius. Local recurrence at the site of the primary bone tumor tumor occurred in seven patients (54%) before pulmonary metastases developed. The mean interval from the diagnosis of the primary bone tumor to the onset of pulmonary metastasis was 3.8 years, with a maximum of 10.7 years. Fifty-four percent of the patients (7/13) had pulmonary metastases 3 years after diagnosis of the primary bone lesion, and 92% (12/13) had pulmonary metastases 7.5 years after diagnosis. Overall mortality rate directly due to giant-cell tumor and its metastases was 23%. On chest radiographs and CT scans, pulmonary metastases appeared as rounded, nodular opacities of homogeneous density, ranging from 0.5 cm to 8.0 cm in diameter. Peripheral regions of the lungs were involved in 85% of the cases and basilar regions in 62%. Our study shows that benign giant-cell tumor of bone can produce pulmonary metastases, that metastases most often occurred with recurrent local disease and distal radial lesions, that the prognosis was relatively favorable, and that such metastases had no distinguishing radiologic features.

Short-term memory, parsing, and the primate frontal cortex.

Removal of the frontal cortex of primates resulted earlier in a psychological deficit usually classified in terms of short-term memory. This classification is based on impairment in performance of delayed-response or alternation-type tasks. We report an experiment in which the classical 5-seconddelay right-left-right-left (R-L-R-L) altenation task was modified by placing a 15-seconid interval between each R-L couplet: R-L . . . R-L . . . R-L . . . . This mnodification made it possible for monkeys with frontal lesions, which had failed the classical task, to perform with very few errors. The result suggests that proper division, parsing of the stream of stimuli to which the organism is subjected, is a more important variable in the mechanism of short-term memory than is the maintenance of a neural trace per se.