Nail Unit Glomus Tumor with Myxoid and Symplastic Change Presenting with Longitudinal Erythronychia.

Glomus tumors are soft tissue neoplasms, which are most frequently encountered in the nail unit and generally straightforward to diagnose by histopathology. The typical clinical presentation is that of a circular violaceous or erythematous lesion within the nail bed. However, there are rare variants of glomus tumors which may pose diagnostic challenges because of the presence of unusual histologic features. Herein we report such a glomus tumor that demonstrates the rare combination of both myxoid and symplastic change. The clinical presentation of longitudinal erythronychia, as seen with this case, can occur with glomus tumors, but it is unusual, as longitudinal erythronychia on a single nail usually is caused by an onychopapilloma. The distinct nuclear atypia characteristic of symplastic change can raise alarm for a malignant process but the clinical course is benign. It is essential for dermatopathologists to be aware of this unusual variant of a glomus tumor in order to avoid overdiagnosis of atypia, which could result in unnecessary aggressive surgery. While unusual, there is good clinicopathologic correlation of the glomus tumor presenting with longitudinal erythronychia.