(Nodules; Small tumors; Tuberculae)
Definition. Tubercles are solid, circumscribed, rounded, pea-to cherry-sized, cellular infiltrations of the corium or subcutaneous tissue.
Tubercles consist of cellular infiltration and are usually neoplastic as in leprosy, lupus and syphilis but they may be of a hypertrophic or inflammatory nature. They may be more or less elevated above the surface, have well-defined borders, conical or flat tops and correspond to papules in color, shape and other variations. However, they differ from papules in size, in their origin in a deeper part of the skin, slower course, and less tendency to spontaneous resolution. From their deeper seat they may project upon the skin in a less degree than papules; they may be fixed in the skin by a broad base; or they may have a narrow attachment and largely protrude upon the surface. Tubercles some- times become diffuse from peripheral extension and coalescence, and may involve the subcutaneous tissues as well as the skin. Ulcerating or degenerating tubercles lead to considerable destruction of tissue and consequent scarring of the skin when repair ensues. The word tubercle, designating a form of lesion, should not be confused with the pathological condition known as tuberculosis; or with growths, usually of larger size, known as tumors. In dermatology the term tubercle refers to the size and general features of the lesion and not to its pathological nature.