A Transplantable Metastasizing Chondro-Rhabdo-Myo-Sarcoma of the Rat

Abstract

With the exception of certain mixed tumors of the testis, ovary, and kidney, neoplasms containing striated muscle are very infrequent in man, and only a few have been described in animals. In a comprehensive review of the literature on animal tumors, in 1896, Caspar (1) mentioned but 3 cases of rhabdo-myomata, i.e., a melanotic rhabdo-myoma of the tail and perianal connective tissue of a stallion, reported by Kolessnikoff; a rhabdo-myoma of the vagi of a horse, described by Gratia; and an adeno-sarco-rhabdo-myoma of the kidney of a hog found by Johne. J. Wolff (2) cited a case of rhabdo-myoma of the shoulder of a horse, discovered by Monod, and Magnusson (3), quoting Boncek, reported an adeno-rhabdo-myoma of the heart of a cow. A giant-cell rhabdo-myo-sarcoma of a trout was described by Adami (4), and Fibiger (5) has reported a rhabdo-myoma of the codfish. However, the rat tumor described in the present paper is apparently the first rhabdo-myoma to be recorded in a rodent, in spite of the number and variety of neoplasms which have been observed in rats and mice. This tumor is interesting not only for its rarity, but also because of its morphology and its biological character. The growth was found in a black and white female rat, between fifteen and nineteen months old, of a group of animals experimentally infested with Cysticercus fasciolaris. This rat, however, had not developed sarcoma of the liver. When first observed the tumor was a small circumscribed hemispherical mass about the size of a pea, situated beneath the skin of the upper epigastrium, in the median line of the body. It was firm and elastic and was apparently adherent to the ensiform process of the sternum. During the first few weeks of observation there was no material increase in size of the tumor, but at the end of two months, when the animal was mated, it was noted that the mass had grown slightly. Three weeks later the rat was isolated pregnant, and it was then recorded that the tumor had about doubled in size since the last observation. The rat gave birth to two young, only one of which she reared. Throughout lactation and subsequently the tumor grew rapidly. One month after gestation, a fragment of tumor was surgically removed, and was used for the subcutaneous inoculation of 93 rats. At this time the growth measured 5.5 × 3.5 × 3 cm. The rat survived the operation thirty days, during which period the tumor grew with great rapidity attaining a size of 6.5 × 5.9 × 4.4 cm. At autopsy the growth surrounded and largely replaced the ensiform process, its capsule being closely adherent to the sternal end of the two caudal pair of ribs. It was irregularly nodular, distinctly lobulated, and covered by a thin fibrous capsule. The consistency was firm and tough, with small soft and cartilaginous areas scattered throughout. In certain parts the tumor was friable and short plugs of tissue could be expressed from the cut surface by pressure. The color was grey white to pinkish, with small scattered areas of hemorrhage and large and small patches of necrosis. Gross metastatic tumor deposits were present in the lungs.