Kidney stones, also called renal calculi, are solid concretions (crystal aggregations) of dissolved minerals in urine; calculi typically form inside the kidneys or bladder. The terms nephrolithiasis and urolithiasis refer to the presence of calculi in the kidneys and urinary tract, respectively.
A sebaceous cyst is a closed sac under the skin filled with a cheese-like or oily, semi-solid material called sebum. Sebum is produced by sebaceous glands of the epidermis. A foul odor is also often present in the substance called keratin which fills sebaceous cysts. Keratin is a protein that