A case of malignant glomus tumor requiring differentiation from skin metastasis of thyroid cancer and gastric leiomyosarcoma.

Abstract

Glomus tumors are generally benign tumors that are located in the nail beds and other peripheral areas of the extremities and are often painful, but there are ones with findings suggestive of malignancy, such as atypical mitotic figures and infiltrative growth. The patient is a 69-year-old woman. About 8 years ago, she was diagnosed with papillary thyroid cancer and underwent a total thyroidectomy. At that time, multiple lung metastases were found, and thyroid stimulating hormone suppressive therapy was administered. About one month before her first visit, she was admitted to the Department of Gastroenterology because of increased lung metastasis, progressive anemia, and black stools. A gastric endoscopy was performed, and an elevated lesion was found on the gastric wall. At the same time, she was referred to our department for consultation because of a 15-mm sized, smooth-surfaced, easily hemorrhagic red nodule on the ventral side of the right middle finger. Cutaneous metastasis was suspected following simple excision for diagnostic purposes. Grossly, the tumor was a dense mass covered with a thin capsule, and pathologically, it was densely proliferating in the dermis layer with atypical cells with round nuclei and weakly acidic, relatively broad reticulum, and many atypical mitotic figures were seen. Immunostaining showed that tumor cells were negative for CD34, CD68, AE1/AE3, CK7, CK20, TTF-1, thyroglobulin, LCA, S-100, HMB-45, CEA, GCDFP-15, desmin, weakly positive for Melan-A, positive for α-SMA, vimentin, and MIB-1 labeling index of about 40%. Based on these results, a diagnosis of malignant glomus tumor was made. Malignant glomus tumor is a rare disease, and the clinical course and pathological findings required differentiation from thyroid cancer or skin metastasis of gastric leiomyosarcoma in our case.