26 BULLETIN 1449, U. S. DEPARTMENT OF AGRICULTURE 
GIANT-CELL OR MYELOID SARCOMA 
Giant-cell sarcomas are neoplasms characterized by the presence of 
multinuclear or giant cells, which are identical with myeloplaxes of 
bone marrow and are intermingled usually with the cells of spindle- 
cell sarcoma and sometimes with the cells of round-cell sarcoma. 
Giant-cell sarcoma, unlike other forms of sarcoma, is encapsulated, 
practically nonmalignant and not known to metastasize or to recur 
after removal. The giant cells of sarcoma are irregularly jagged in 
outline, often large, and may be from 10 to 30 times the size of 
leucocytes. They often have vacuoles and fat drops. The nuclei 
may be few in number or very numerous, since as many as 100 have 
been observed in a single giant cell. The nuclei in giant-cell sar- 
comas are scattered in the interior and all through the cytoplasms of 
the cell, and not at the periphery, as is the "case in the degenerative 
type of giant cells found in tuberculosis or around foreign bodies. 
Giant-cell sarcoma has an extensive supply of capillary vessels from 
which blood extravasations may often take place. These extravasa- 
tions give the neoplasm a brownish-red color. Giant-cell sarcoma 
is moderately firm, slow of development, and often even hard to the 
touch. In those starting from the bone marrow the hemorrhagic 
condition may be so abundant as to be mistaken for blood clots re- 
sembling currant jelly. Besides the ordinary type of giant-cell sar- 
coma originating from the periosteum of the jaw or the long bones, 
there is one variety that occurs in the gum and is known clinically 
as epulis. It is not uncommon in man, but is rarely found in domes- 
tic animals. 
OSTEOSARCOMA 
Osteosarcoma is sarcoma containing osseous tissue. During the 
early stages of its growth spindle-shaped sarcoma cells are inter- 
mingled with a variable quantity of immature bone and often with a 
few giant cells. Osteosarcoma is rapid in growth and malignant in 
nature. It is not uncommon in domestic animals especially in the 
maxillary bones. The neoplasm infiltrates into the epiphyses of long 
bones and extends also into the shaft of the bone, replacing the bone 
structure by imperfect osseous material. During the growth ab- 
sorption of the bone from the periphery takes place. The tissue 
absorbed is replaced by an osteoplastic process, which must have 
been the initial condition responsible for the growth of the neoplasm. 
Different portions of the growth show microscopically various cells, 
such as sarcomatous spindle cells intermingled with cartilage cells, 
imperfect bone lamellae, and atypical bone cells without branching, 
which indicate rudimentary bone formation. 
Some forms of sarcoma of periosteal origin become intensely ma- 
lignant. This type has a strong tendency toward calcification but 
not for true ossification. Metastases to serous membranes and the 
lung are not common. Some writers describe this type by the name 
of osteoid sarcoma. 
MELANOTIC SARCOMA 
Melanotic sarcoma is a pigmented, malignant neoplasm. The 
names " melanoma " and " melanosarcoma " are synonymous. These 
neoplasms are common in man but even more frequent in domestic 
