Juxtacortical Glomus Tumor of the Tibia with an Uncertain Malignant Potential

ABSTRACT

Glomus tumors are mesenchymal neoplasms that are composed of modified smooth muscle cells of the normal glomus body. Most glomus tumors are benign and they occur in the distal extremities, and particularly the subungual lesions that occur in the hand, the wrist and the foot. We report here on a case of a solid type glomus tumor that had an uncertain malignant potential with a juxtacortical location at the distal tibia, and there were no neoplastic erosion of the cortical surface and no periosteal reaction. The tumor cells showed mild nuclear atypia and moderate mitotic activity (3-5/10HPF). Prominent intranuclear cytoplasmic pseudoinclusions were also observed. This case is interesting due to the very unusual tumor location of the juxtacortical area of the long bone, the atypical histologic features and the unique cytological finding of cytoplasmic intranuclear inclusions throughout the tumor cells.