Myositis ossificans traumatica(MOT) in head and neck area is a rare non-neoplastic, heterotopic bone formation within a muscle, arising after trauma or surgery. Although the several case reports have described the occurrence of MOT in other muscles of oro-facial musculature, MOT has never been reported in mentalis muscle. We demonstrate a case of MOT occurred in mentalis muscle of a 64 years old male. He recently complained of a movable mass with no pain. He had experienced a hitting trauma on his right anterior mandible about 25 years ago. Since then, the trauma area has been asymptomatic. The lesion showed severe muscular degeneration, resulted in a pseudocystic change without epithelial lining. The ectopic ossification was closely associated with the fibrous fascia of adjacent muscles. The lesion contained a lot of basophilic materials admixed with atrophying cells, which were supposed to be derived from muscle parenchyma injured previously. It was presumed that the basophilic materials induced callus-like ossification in the fibro-muscular lesion, also recruited macrophages and fibroblasts. However, the ossification processes in MOT were predominantly characterized by dystrophic calcification without osteoblastic differentiation of mesenchymal cells. Even more, there appeared some skeletal muscle bundles which were calcified dystrophically. Therefore, we suggest the present case of MOT might be initiated by dystrophic calcification in the degenerating muscle tissue

A Truncatipennes species, Pentagonica subcordicollis Bates is newly recorded in Korea. Here we provide a diagnosis and systematic accounts of P. subcordicollis. Consequently, a total of three species of Pentagonia have been recorded in the Korea, including the present species.