True bony tumors of the skin must be differentiated from calcareous deposits which are the result of chronic inflammatory processes. Heidingsfeld* has briefly reviewed some of these cases in addition to reporting one of his own. The growths probably arise from congenitally misplaced bone cells. The growths are always small, and usually occur in connection with other lesions. Histologically, they show typical bone structure. They may be removed by operation.
*Heidingsfeld: Jour. Amer. Med. Assn., 1913, lxi, 405. •Heidingsfeld: Jour. Arr.er. Med. Assn., 1907, xlviii, 562.