Malignant Glomus Tumor Arising in Benign Glomus Tumor

ABSTRACT

The glomus tumor is a distinct neoplasm composed of modified perivascular smooth-muscle cells identical to those described in the glomus body. Malignant glomus tumor, also referred to as glomangiosarcoma, is exceedingly rare. It has been subdivided into locally infiltrative glomus tumor, glomangiosarcoma arising in a benign glomus tumor, and glomangiosarcoma arising in de novo. A few cases of malignant glomus tumor arising in a benign glomus tumor have been reported. A 55-year-old man underwent resection of a solitary nodule in the right shoulder area. The tumor was biphasic with a typical benign glomus tumor at the periphery and the central sarcomatous area composed of oval to elongated pleomorphic cells with a single prominent nucleolus and occasional mitotic figures. Both tumor components showed intense staining for vimentin, smooth muscle actin, and muscle specific actin. Herein, we report a case of a malignant glomus tumor arising in a benign glomus tumor with an immunohistochemical study and a review of literatures.