36 
BULLETIN 144&, U. S. DEPARTMENT OF AGRICULTURE 
inflammation of the lymp vessels and glands so closely that it re- 
quires a microscopic examination to tell them apart. 
DISTINCTION BETWEEN CARCINOMA AND SARCOMA 
According to the histogenetic classification of neoplasms, a sharp 
line of distinction exists between sarcomas, which are mesoblastic or 
of connective-tissue origin, and carcinomas, which are of epiblastic 
or epithelial origin. As a matter of fact, however, certain neoplasms 
which are classed as sarcomas (alveolar) show a histological struc- 
ture which resembles carcinoma so closely that in a single slide and 
without the history it is difficult to distinguish one from the other. 
Transplantation experiments of carcinoma in mice have shown 
that carcinomas become changed into sarcomas after 12 or 14 suc- 
cessive generations of transplantation. 
Some of the textbooks on pathology have tables of the diagnostic 
features of sarcoma and carcinoma. The following points may be 
helpful in distinguishing between sarcoma and carcinoma : 
Sarcoma 
Carcinoma 
1. Origin. — Mesoblast (connective 
tissue). 
2. Cells. — Embryonal connective-tis- 
sue cells. 
3. Intercellular substance. — May be 
present. 
4. Stroma. — Intercellular stroma 
rarely forms alveoli. 
5. Blood supply. — Vessels are embry- 
onic, often mere channels in contact 
with the cells. No muscle in the walls. 
6. Metastasis. — Ordinarily by blood 
vessels, exceptionally by lymph ves- 
sels. 
7. Malignancy. — Marked. 
8. Usual seats. — Primary sarcoma 
is generally found in connective tis- 
sues, as corium, fasciae, periosteum, 
brain, ovary, rarely in liver, lung, and 
uterus. Occurs primarily in lymph 
glands but not by metastasis. 
9. Sensitiveness. — Usually not pain- 
ful. 
10. Age. — Occurs usually in the 
young. 
11. Growth. — Often interrupted. 
12. Shape. — Often rounded, flesh- 
like masses. 
13. Heredity. — Rarely hereditary. 
1/f. Secondary changes. — Myxoma- 
tous degeneration common. Calcifica- 
tion and pigmentation very common. 
Ossification and condroid not so com- 
mon. No fat within the neoplasm. 
Epiblast or hypoblast and meso- 
blast (both epithelium and connective 
tissue). 
Epithelial cells contained in alve- 
oli, varying in shape and size. 
Absent, or merely fluid. 
Connective tissue forms commun- 
cating alveoli in the course of lym- 
phatics. 
Vessels well developed, contained 
within and supported by the walls of 
the alveoli. Seldom in contact with 
the cells. Have distinct muscle walls. 
Usually by lymph vessels, but in 
later stages also by blood vessels. 
Very marked. 
Primary cancers occur on epithelial 
surfaces and in glands, especially on 
the lips, in mammary gland, stomach, 
intestines, uterus, vagina, and penis. 
Can be carried to any tissue by me- 
tastasis. Does not occur primarily in 
lymph glands but is usually present 
secondarily. 
Always painful. 
Generally occurs in middle life or 
later. 
Continuous, often rapid. 
Nodular, tubular, dendritic, often 
ulcerating on surface. 
Often hereditary. 
Fatty degeneration very common, 
almost from the start. Mucocolloid 
frequent. Pigmentation rare. Cystic 
change rare. Fat may be present 
within the cancer tissue. 
