(a) Sebaceous horns, quite common, arising by protrusion of contents of a sebaceous cyst through a rupture in its wall or through its duct, with consequent desiccation by exposure to the air, while fresh material is consequently added at the basis so long as sebaceous secretion continues. These growths soften when soaked in weak liquor potassæ.
(b) Warty horns, structurally identical with the above, but growing from warts instead of from sebaceous cysts. Both these forms are often found about the head. Cutaneous horns are also met with in ovarian dermoids. They are common in the lower animals and may attain large size.
(c) Horns growing from cicatrices, especially of bones, are rare, but a cornified condition of the cicatrix itself, with formation of scales resembling those from horns, is not uncommon.
(d) Nail horns are simply overgrown nails, occurring on the digits and toes of bedridden patients who never walk ([Fig. 87]).
Fig. 87
Nail horns. (Original.)
Treatment.
—All these forms of epithelial outgrowth call for radical removal, which implies complete extirpation of the membrane or tissue from which the growth occurs, after which, if effected, there is no recurrence. If some be left there is tendency to recedive.