of tumors the benign tumors will be considered first, as the tissues of which they are composed bear a closer resemblance to normal tissue than do the tissues of malignant tumors, and hence the deviation from the laws governing normal growth and nutrition is less marked.

}

Teratomata.

3. Epiblastic, hypoblastic, and

mesoblastic tumors.

4. Swellings caused by reten

tion of physiological se- Retention-cysts.

cretion.

XIII. PAPILLOMA AND ONYCHOMA.

PAPILLOMA.

A PAPILLOMA is a non-malignant epithelial tumor of the cutaneous or mucous surface. The essential part of the tumor is composed of epithelial cells; the framework is furnished by the connective tissue underneath the epithelial proliferation. The tumor-tissue proper is outside the limits of the vascular area, being separated from it by the membrana propria. The tissues of the epiblast and the hypoblast possess no independent organ-producing power, as their blood-supply is derived from the mesoblast. Epithelial cells in the normal mesoblast have no power to proliferate, hence in cases in which we find them multiplying here the mesoblast has undergone changes. The epithelial cells receive their nourishment from the blood-plasma and the leucocytes. As the stroma of an epithelial tumor is derived from the mesoblast, an epithelioma is a mixed tumor, in which, however, in accordance with the law of the legitimate succession of cells, the epithelial cells are derived from the epiblast or the hypoblast, and the connective tissue from the mesoblast. The development of new tissue from these sources is usually unequal: sometimes the product of one, and sometimes that of the other, predominates. The unequal representation of the two different tissue-elements, epithelial cells and connective tissue, in this form of tumor has given rise to a great deal of confusion in classification. As papillary formations are found in many tumors not belonging to this variety, and as in many specimens fibrous tissue predominates, Virchow objected to papilloma as a separate variety of tumors. Rokitansky also treated papilloma as a variety of fibroma. Virchow proposed the name fibroma papillare. However, in most tumors which deserve the designation "papilloma" the epithelial elements predominate and impart character to the tumor-the reticulum, if it predominates, being an accidental product. It is the intention of the writer to show, as far as possible, in connection with every variety of tumors, the counterpart in the normal tissues of the body. A papilloma of the skin under low power presents in a hypertrophic condition all the tissues of which the skin is composed.

Histology and Pathology.-Papilloma of the skin, as shown in Figures 54 and 55, represents the same papillary structure as the skin,

the number of papillæ depending on the size of the tumor. In papilloma of the hypoblast the villi correspond with the papillæ of the epiblastic papilloma. The connective tissue and the vessels occupy the centre of the papillæ (Fig. 55, a), and present, on vertical section of the tumor, finger-like projections conical in shape, the base corresponding with the base of the tumor, and the apex with the summit of each papilla. The epiblastic papilloma is covered by stratified layers of squamous epithelial cells. The new cells are produced near the vascular territory (Fig. 55, 6). As the cells become older they lose the liquid part of their contents by exposure on the surface and by more

FIG. 54.-Section of human skin (after Piersol): a, stratum corneum; b, stratum lucidum; c, stratum granulosum; d, stratum Malpighii; e, f, papillary and reticular layers of corium; g, stratum of adipose tissue; h, i, spiral and straight portions of duct of sweat-gland; k, coiled portion of sweat-gland; 4, vascular loops occupying papillæ of corium.

distant removal from the vascular supply, forming the horny layer of the papilloma (Fig. 55, c). The papilloma of the hypoblast is composed of a connective-tissue stroma, usually softer and more vascular than that of epiblastic papilloma, and of cells corresponding in type to the cells of the mucous membrane in which the tumor is located. The pavements of cells which constitute the essential part of the tumor are made up of cylindrical cells. As hypoblastic tumors are constantly exposed to maceration by the contents of the hollow organs in which they are located, the epithelial cells become cedematous and are very liable to undergo myxomatous degeneration. Even by excluding the papillo

mata of inflammatory origin, we have, so far as the texture of the tumor is concerned, two varieties-(1) hard and (2) soft. The density of a papilloma depends on the amount and character of the stroma and the location of the tumor. If the stroma is abundant and compact,

FIG. 55. Papilloma of skin; X 50 (Surgical Clinic, Rush Medical College, Chicago): a, connective tissue; b, embryonic epithelial cells; c, old squamous epithelial cells.

and if the tumor is not exposed to maceration by constant moisture, the tumor is firm; on the contrary, if the stroma is scanty, if the connective-tissue fibres are loosely arranged and vascular, and if the epithelial cells, by constantly imbibing moisture from their environment, become cedematous, the tumor is soft. The former conditions are most frequently presented by tumors of the skin and of mucous membranes derived from the epiblast, and the latter condition by tumors of mucous membranes lining hollow viscera and paved with columnar epithelium. In some instances a papilloma is covered by columnar epithelia if the tumor occupies a location surrounded by squamous epithelia. Hard papillomata are found most frequently in the skin and in the mucous membrane of the lip, mouth, soft palate, nose, larynx, urethra, vagina, and cervix uteri. The soft variety is found most frequently in the mucous membrane of the intestinal canal and of the bladder. If a number of papillomatous tumors develop simultaneously

or in succession in the same neighborhood, they form tumor-masses of greater or less circumference with a mushroom-like surface. The papillary excrescences are often branched, producing the so-called "dendritic vegetations." This condition is often found upon mucous surfaces. If the papilloma is not subjected to injury and is otherwise surrounded by favorable conditions for rapid growth, it often elongates into a delicate filamentous tumor, as is frequently seen in the bladder. The connective-tissue core conveys vessels and nerves to each papillary growth, the vessels forming loops as in the papillæ of normal skin and in the villi of the intestinal mucous membrane. In papillary growths in joints the vessels are absent. In benign epithelial tumors of the skin we often find epithelial cells in concentric layers arranged in pearl-like masses, a proof of the independent proliferation of the epithelial cells. A papilloma never attains great size, large tumors of this kind being met with only as a result of the confluence of a number of tumors. By the aggregation of numerous tumors, masses the size of a fist are observed in the rectum and upon the prepuce and the labia majora. An individual tumor seldom exceeds the size of a cherry. The growth of a true papilloma is always very slow, papilloma manifesting in this respect much less activity than infective papillomatous growths. Among the degenerative processes which most frequently affect papillomatous tumors are cretefaction, myxomatous degeneration, and ulceration. Cretefaction often arrests the further growth of a papilloma of the skin. Myxomatous degeneration most frequently attacks tumors of hypoblastic origin. Ulceration is the result either of mechanical irritation or of infection with pathogenic microbes through an abrasion or a fissure of the surface of the tumor. If in a pedunculated papilloma the principal artery becomes thrombosed, either in consequence of an injury, such as twisting of the pedicle or traction, or as one of the results of an accidental inflammation, gangrene of the tumor is produced, usually resulting in a permanent cure. Psammoma is very prone to undergo calcification which limits tumor-growth-a fortunate occurrence, considering the importance of the locality occupied by such

tumors.

Transformation into Malignant Tumors.-Of all tumors, papillomata are most liable to undergo malignant transformation. The irritation to which such tumors are frequently exposed by their location upon a surface will account satisfactorily for this well-established clinical fact. This transition is observed most frequently in tumors which occupy localities most exposed to irritation. We seldom hear of a papilloma of the cavity of the mouth undergoing such a transformation, while carcinoma frequently originates in a papilloma of the lip. Papilloma constitutes.