Primary intraosseous glomus tumor in a middle phalanx

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IntroductionThe glomus tumor is a benign neoplastic proliferation ofglomuscells,whicharemodifiedperivascularsmoothmusclecells [1–3]. The lesion characteristically occurs in a digitalsubungual location, and presents with pain exacerbated bytemperature change. Although glomus tumors are thought toarise from glomus cells, these tumors have been observed inextracutaneous locations that are not known to containglomus cells, including the nose, eyelid, middle ear, lung,mediastinum, stomach, rectum, cervix, penis, and bone [2,3]. One possible explanation for this finding is that thesetumors may arise from perivascular cells that can differen-tiate into glomus cells [4]. Primary intraosseous glomustumor, which is rare and usually reported in the distalphalanx, has a place in the differential diagnosis of osteolyticlesions of the phalanges [5–7]. To our knowledge, only onecase has previously been documented in the middle phalanx[8], and this did not include a description of advancedimaging techniques. Here, we describe the imaging appear-ances and treatment response of a case of primary intra-osseous glomus tumor located in the middle phalanx of theindex finger, including the previously unreported computedtomography and magnetic resonance features.Case reportAn otherwise healthy 51-year-old woman was evaluated forincreasing pain in the index finger of her left hand. Thepain was worse at night with no particular exacerbatingfactors. There was no history of trauma or prior surgery.Physical examination revealed a tender prominence justdistal to the proximal interphalangeal joint of the left indexfinger. Plain radiographs showed a well-circumscribed,radiolucent lesion that involved the medullary cavity andproximal epiphysis of the middle phalanx, producing deependosteal erosion of the adjacent cortex (Fig. 1). Theproximal and distal interphalangeal joint spaces werepreserved. Computed tomography (CT) exhibited a well-defined osteolytic lesion involving the middle phalanx in itsentirety, with no evidence of matrix calcification (Fig. 2).The lesion extended to the subchondral bone of theproximal interphalangeal joint. In addition, two focal areasof cortical breach were identified at the medial aspect of thebase of the phalanx and at the lateral aspect of the distalphalangeal diaphysis respectively. At magnetic resonance(MR) imaging, the lesion demonstrated intermediate signalon T1-weighted images, and markedly hyper-intense signalon T2-weighted images (Fig. 3). After intravenous contrastmedium injection, the tumor displayed homogeneous