32 BULLETIN 1449, U. S. DEPARTMENT OF AGRICULTURE 
Structure. — Microscopic sections of squamous epithelioma show a 
perverted state of epithelial hyperplasia. In neoplasms from the 
skin the epithelium of the stratum Malpighii proliferates, forming 
cylindrical cords which extend inward and penetrate and invade the 
underlying connective tissue. These branching cords, though ex- 
tending in different directions, are continuous with one another in 
sections and may show the epithelium in cylindrical groups or nests. 
The outer cells of these cords, which are in contact with the stroma, 
are cuboid or cylindrical, resembling the cells of the stratum germi- 
nativum. The cells in the interior of the cords are polyhedral, often 
larger in size than the cells found normally in the skin and resem- 
bling prickle cells. The inner cells, which are the oldest, are flat- 
tened, cornified, and homogeneous in appearance. They form con- 
centric or lamellar groups that are known as " pearly bodies," which 
constitute the definite characteristic of squamous epithelioma in 
sections. 
In man a special form of squamous epithelioma of the face about 
the eyes and nose has been described by some pathologists under 
the name of " basocellular cancer." This neoplasm is almost benign 
and shows no tendency to infiltrate the surrounding tissues. This 
form of epitheliomas has not been described in domestic animals. 
The epithelial cords of squamous epithelium are separated by a 
variable amount of interstitial connective-tissue stroma. The stroma 
may be abundant or scanty, and is the tissue which contains the blood 
vessels and lymphatics. The stroma may consist of loose fibrous 
tissue or may be composed of tissue rich in cells. When ulceration 
affects the epithelial portion, the stroma becomes the seat of in- 
flammatory cell infiltration. 
CYLINDRICAL EPITHELIOMA 
Definition. — Cylindrical epithelioma is a form of carcinoma which 
originates on surfaces lined by columnar epithelium or from glands 
of the columnar-cell variety. 
Seats. — Cylindrical epitheliomas are found most frequently in the 
mucous membrane of the gastrointestinal tract and of the uterus, at 
the pyloric end of the stomach, at the ileocecal valve, and in the 
rectum, at the junction of the columnar epithelium with the squamous 
epithelium. The location last mentioned is considered the typical 
seat for the occurrence of cylindrical epithelioma. Less frequently is 
this neoplasm found in the mammary gland, the respiratory tract, 
kidney, and liver. 
Nature and structure.— Cylindrical epitheliomas are soft to the 
touch, grow rapidly, are often papillary, and frequently ulcerate in 
the interior. They readily undergo degeneration, especially mucoid 
change, which makes them more malignant. On microscopic examin- 
ation cylindrical epithelioma is seen to consist of columns resembling 
tubular glands. A lumen may be present between the rows of cells. 
When the columnar cells proliferate the tubular structure may con- 
sist of several rows of cells, the outer row retaining the columnar 
shape while the inner cells may be irregular, but the cylindrical 
epithelioma retains the tubular shape. When the lumen becomes 
distended the appearance is not unlike that of an adenoma. 
