Abstract

Glomus tumor (GT) is a painful benign neoplasm arising from perivascular-modified smooth muscle cells of glomus body. It occurs at any location of the body with a predilection of the subungual region and on rare occasions affects peripheral nerves. Only two collision tumors involving GT were reported in the lung and thigh; (1) a mixed squamous cell and glandular papilloma and GT and (2) a malignant glomus tumor and a fumarate hydratase (FH)-deficient leiomyoma respectively. Herein we present a 41-year-old male patient with a past medical history of psoriasis, presenting with a left thumbnail nodule status post-trauma. A 3 mm punch skin biopsy demonstrated a deep dermal well-demarcated, bland spindle cell proliferation arranged in a loosely fascicular growth pattern with increased vasculature. The spindle cells showed hyperchromatic wavy nuclei set in myxocollagenous stroma. Within the spindle cell proliferation, a second distinct population of round to ovoid cells was noted arranged in nests and cords surrounding irregularly spaced vascular channels. The cells demonstrated mild to moderate nuclear atypia with focal hyperchromasia and fragmentation. No mitotic activity was identified. Immunohistochemical studies revealed the spindle cell population was diffusely positive for SOX10 and S100, while the 2nd cell population was positive for SMA.  A diagnosis of an atypical glomus tumor arising in association with a traumatic neuroma was rendered. To our knowledge, only two cases of collision tumors involving GT were reported. Our case is the first case of atypical glomus tumor arising in association with traumatic neuroma.