Abstract
On May 10, 1915, a large male guinea-pig which had seemed to be in good health in the morning became suddenly ill in the afternoon and died within a short time. The animal had been injected some months previously with a culture of what was supposed to be diphtheria bacilli, but it had survived the injection. At autopsy a large freely movable mass was found in the mid-line of the neck on the ventral surface, which was adherent to the underlying tissues about mid-way between the lower jaw and the shoulder girdle. The tumor was apparently encapsulated and showed no attachment to the skin. It measured 3 1/2 × 2 1/2 × 2 1/2 cm. in the various diameters, was yellowish in color and quite firm. The capsule was fibrous and cut with some difficulty, but the central portion was quite friable. The cut surface was yellow with many mottled patches which were dark red in color.
Surrounding the tumor and in the right axilla were a number of metastatic nodules, the largest of which measured 1 1/2 × 1 × 1/2 cm., and the smallest being about the size of a grain of wheat. Section of the larger nodules showed a cut surface which was identical with that of the large tumor.
The thoracic and abdominal organs showed nothing unusual.
On microscopic examination the body of the tumor is seen to consist of round and ovoid cells which vary considerably in size. In places the cells are closely packed together but in others they are separated by a reticulum of connective tissue. There are many large areas of necrosis in which practically all cellular structure is lost. There is evidence of an unsuccessful attempt at encapsulation, but the tumor has invaded the connective tissue of the capsule as well as the adjacent areolar tissue.
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