Glomus tumors are rare mesenchymal neoplasms with a phenotype akin to the modified smooth muscle cells of the glomus body. Most are benign, but rare examples show malignant histologic characteristics and aggressive behavior. We recently encountered a malignant glomus tumor with BRAF V600E mutation. We sought to study a large cohort for this mutation, with particular attention to associated malignant histologic characteristics. Tumors were classified based on WHO criteria as benign, uncertain malignant potential (glomus tumors of uncertain malignant potential-GT-UMP), or malignant. Tumors were screened for BRAF V600E by immunohistochemistry, and positive staining was evaluated further by Sanger sequencing. A total of 102 glomus tumors were included and classified as benign (57, 56%), GT-UMP (15, 15%) and malignant (30, 29%). Tumors occurred in patients aged 8 to 89.9 years (median: 50.2), without sex predilection (55% men). Most occurred in the superficial soft tissue (84%) and upper extremities (55%). Six of 95 tested cases had BRAF V600E mutation (6%), including 0 of 57 benign tumors, 3 of 14 GT-UMP (21%), and 3 of 24 malignant tumors (12%). Follow-up was obtained for 59 cases (median: 75.7 mo, range: 7.8 to 268.5). Three of 11 malignant tumors (27%) had progressive disease: 1 with metastasis to brain and heart, 1 with enlarging residual disease, and 1 with recurrence. Two of 4 GT-UMP (50%) had progressive disease: 1 with metastasis to lung, and 1 with local recurrence (50%). Three of 44 benign tumors (7%) had local recurrence. Two of 5 patients with BRAF V600E had progression, including 1 GT-UMP with local recurrence and 1 malignant tumor with enlarging residual disease. In summary, BRAF V600E mutation was detected in 6% of glomus tumors, all of which were malignant or GT-UMP. This mutation may be associated with a malignant phenotype, although study of additional cases is needed. In patients with progressive disease, BRAF could be a promising therapeutic target.
Adamantinoma represents a distinct group of bone tumors showing both mesenchymal and epithelial differentiation most commonly involving the tibial diaphysis. Most adamantinomas contain a fibro-osseous component and an epithelial component consisting of squamous or basaloid cells. Adamantinomas are considered malignant neoplasms requiring en bloc excision that frequently recur locally and can rarely metastasize. Rare adamantinomas show an epithelial component consisting predominantly of monomorphic spindle cells, which, combined with an epithelial immunophenotype, can mimic monophasic synovial sarcoma. Synovial sarcoma is very rare in bone. It is considered a high-grade sarcoma that typically necessitates chemotherapy. However, the relationship between spindle cell adamantinoma and intraosseous synovial sarcoma has not been investigated. The current study was prompted by identification of a presumed spindle cell adamantinoma of the tibia with diffuse keratin expression that harbored a SS18 gene region rearrangement. FISH of eight additional bone tumors initially classified as spindle cell adamantinoma based on clinicoradiopathologic findings revealed one additional case with SS18 rearrangement. Histologically, both intraosseous synovial sarcoma and spindle cell adamantinoma demonstrated uniform fusiform nuclei with scant cytoplasm, short fascicles and low mitotic activity. The adamantinomas, but not the synovial sarcomas, were more likely to show overt epithelial differentiation in the form of pseudoglands or squamous nests. Immunohistochemistry of all cases, irrespective of SS18 status, showed diffuse keratin positivity in the spindle cell component, and less consistent EMA positivity. Clinical follow-up was available in both intraosseous synovial sarcomas, one of which recurred and the other metastasized. Two of the six spindle cell adamantinomas with follow-up metastasized. The above findings highlight the morphologic and immunophenotypic overlap between spindle cell adamantinoma and intraosseous synovial sarcoma of the tibia. Investigation of SS18 status to exclude synovial sarcoma is suggested prior to rendering a diagnosis of spindle cell adamantinoma.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.