IMAGING DIAGNOSIS OF SUBUNGUAL GLOMUS TUMOR: A CASE REPORT

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Glomus tumors are rare benign perivascular neoplasms arising from the neuromyoarterial glomus body, a thermoregulatory arteriovenous structure of the reticular dermis. They account for 1-5% of all hand tumors and show a marked predilection for the subungual region of the fingers, with a strong female predominance. Because the classic triad of paroxysmal pain, point tenderness, and cold intolerance is inconstant and the lesion is frequently invisible, diagnosis is commonly delayed by several years. We report the case of a 35-year-old woman, with a history of repeated nail microtrauma related to regular manicures and the use of artificial nails, referred for a three-month history of a painful bluish subungual swelling of the thumb. High-frequency ultrasound demonstrated a well-defined oval nodule of the nail bed that was isoechoic to the adjacent soft tissues and therefore barely conspicuous on B-mode imaging; color Doppler interrogation revealed marked hypervascularity and was the decisive detection tool. Magnetic resonance imaging (MRI) confirmed a small subungual lesion of the distal phalanx, markedly hyperintense on fat-suppressed proton density (PD)/T2-weighted images, hypointense on T1-weighted images, with early, intense, and progressive enhancement on subtracted dynamic contrast-enhanced sequences. The combination of a typical location, marked Doppler hypervascularity, and avid dynamic enhancement was considered diagnostic, and the patient was referred for transungual excision, histological confirmation being pending. This observation illustrates two practical points: in the nail bed, hypervascularity rather than echogenicity is the diagnostic signature of a glomus tumor, and dynamic subtraction markedly increases the conspicuity of a millimetric enhancing nodule.