Answer- D. Myositis ossificansMyositis Ossificans (MO) is an unusual pathological entity still largely unknown, characterized by dystrophic calcification leading to heterotopic ossification of intramuscular connective tissue.DYSTROPHIC CALCIFICATION may occur due to 2 types of causes:Calcification in dead tissueCalcification of degenerated tissue.Calcification in dead tissue:Caseous necrosis in tuberculosisLiquefaction necrosis in chronic abscessesFat necrosis following acute pancreatitis or traumatic fatnecrosis in the breast results in the deposition of calcium soaps.Gamma-Gandy bodies in chronic venous congestion (CVC) of the spleen is characterized by calcific deposits admixed with haemosiderin on fibrous tissue.Infarcts may sometimes undergo dystrophic calcification.Thrombi, especially in the veins, may produce phleboliths.Haematomas in the vicinity of bones may undergo dystrophic calcification.Dead parasites like in hydatid cyst, Schistosoma eggs, and cysticercosis are some of the examples showing dystrophic calcification.Calcification in breast cancer detected by mammography.Congenital toxoplasmosis involving the central nervous system visualized by calcification in the infant's brain.Calcification in degenerated tissues1. Dense old scars may undergo hyaline degeneration and subsequent calcification.2. Atheromas in the aoa and coronaries frequently undergo calcification.3. Mo?nckeberg's sclerosis shows calcification in the tunica media of muscular aeries in elderly people.4. The stroma of tumors such as uterine fibroids, breast cancer, thyroid adenoma, goiter, etc shows calcification.5. Some tumors show characteristic spherules of calcification called psammoma bodies or calcospherites such as in meningioma, papillary serous cystadenocarcinoma of the ovary and papillary carcinoma of the thyroid.6. Cysts that have been present for a long time may show calcification of their walls e.g. epidermal and pilar cysts.7. Calcinosis cutis is a condition of unknown cause in which there are irregular nodular deposits of calcium salts in the skin and subcutaneous tissue.8. Senile degenerative changes may be accompanied by dystrophic calcification such as in coastal cailages, tracheal or bronchial cailages, and pineal glands in the brain, etc.