Atypical glomus tumor of uncertain malignant potential in the urinary bladder

Lindsay L Waters¹, Qihui "Jim" Zhai⁴, J Scott Buie², Rodney Miller², John A Pumphrey³, Sang Wu^2
1Department of Pathology, The Methodist Hospital, Houston, TX, USA; ²ProPath Associates, Dallas, TX, USA; ³Associates of Urology, Fort Worth, TX, USA; ⁴University of Cincinnati and Greater Cincinnati Pathologists Inc, Cincinnati, OH, USA

Abstract: We present a case of an atypical glomus tumor of uncertain malignant potential in an 84-year-old woman with accompanied recurrent low-grade papillary urothelial carcinoma of the urinary bladder. Glomus tumor frequently occurs in the dermis or subcutis of extremities; its morphology includes round cells with pale-eosinophilic cytoplasm and central punched-out round to oval nucleus. Immunostains demonstrate muscle-specific- actin and desmin positivity and CD 34 negativity. Atypical glomus tumors of uncertain malignant potential are defined by lack of frank malignant features, in addition to high mitotic count, superficial location, or large size only, or deep location only. Our case is characterized by an abnormal proliferation of ovoid cells in the lamina propria, uniform ovoid nuclei with indistinct eosinophilic cytoplasm, sheet-like growth pattern with a prominent capillary network, mild nuclear atypia, and high mitotic rate. Immunostains showed tumor cells are positive for smooth muscle actin, smooth muscle myosin, and negative for CD 34. An English literature search revealed only one case of malignant glomus tumor but no atypical glomus tumors occurring in the urinary bladder. We described a case of atypical glomus tumor of uncertain malignant potential occurring in an unusual location, the urinary bladder.

Keywords: atypical glomus tumor, glomus tumor of uncertain malignant potential, urothelial carcinoma, urinary bladder