MRI Need Not Be Ordered Routinely for Suspected Glomus Tumor
Key findings
- Among 54 patients suspected of having upper-extremity glomus tumors, only one clinical factor—lack of paroxysmal pain—was significantly associated with the likelihood of obtaining an MRI
- Management by an orthopedic surgeon was also associated with significantly greater likelihood of obtaining an MRI, perhaps simply due to habit
- Patients who have a visible lesion suspected of being a glomus tumor may not need MRI for confirmation if they have characteristic symptoms
- MRI may be useful when the location or size of the lesion is in doubt or the multifocality of the lesion needs to be ruled out
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Glomus tumors, a rare type of soft tissue tumor, are usually located underneath a fingernail or toenail or in the deep dermis of the palm, wrist, forearm or foot. They characteristically present with a symptom triad of cold hypersensitivity, intense paroxysmal pain and localized point tenderness.
However, due to small size, nonspecific symptoms or atypical site of presentation, glomus tumors often go undiagnosed or remain misdiagnosed for years before treatment. Their symptoms can mimic those of arthritis, neuromas or gout, and alternative diagnoses to consider are cysts, lipomas, melanomas or angiomas.
Glomus tumors are often evaluated with MRI, which has a positive predictive value of 97%. However, a negative MRI doesn't rule out glomus tumor—the negative predictive value (the probability that a patient with a negative MRI truly doesn't have a glomus tumor) is only 20%.
PhD student Claudia Bargon, MD, Chaitanya S. Mudgal, MD, orthopaedic surgeon in the Hand and Arm Center at Massachusetts General Hospital, and colleagues found in a retrospective study that a patient who has a visible lesion suspected of being a glomus tumor probably doesn't need MRI if the symptom triad is present. They published their data in The Archives of Bone and Joint Surgery.
Study Design
The research team searched the pathology database at Mass General and identified 87 adults who had glomus tumors confirmed between January 1990 and February 2015. Their average age was 49 and 52% were male.
54 patients (62%) had a tumor in the arm or hand, of which 30 (55%) were under a fingernail. Of the 33 other tumors, 23 (70%) were in the leg; others were in the back, penis, cheek, trachea, gastric wall, ovary, chest or flank. The median largest dimension was 0.5 cm.
Factors Associated with Ordering MRI
Among patients with upper-extremity glomus tumors, factors significantly associated with an order for MRI were:
- Female gender
- No paroxysmal pain
- Management by an orthopedic surgeon
Tumor size, whether the tumor was visible, whether the patient reported cold hypersensitivity, point tenderness or a painful nail bed were not associated with an order for MRI.
MRI requests by orthopedic surgeons may be attributable to habit, or they may have been likely to request an MRI during the management of glomus tumors because tumors at other sites are often palpable or in other ways more obvious.
Applying the Results to Practice
The role of MRI during the management of a glomus tumor is unclear. Patients who have visible lesions and characteristic symptoms probably will not benefit from MRI. On the other hand, an MRI may be useful when the location or size of the lesion is in doubt or the multifocality of the lesion needs to be ruled out. It may help to be sure that the highest-quality MRI is used and, where relevant, the best possible coil for the finger.
Another dilemma is what to do when the patient's symptoms and examination are characteristic of glomus tumor but the MRI is normal. The surgeon and patient may agree to proceed with surgical exploration, but that can be harmful if one doesn't know where to look. Another option is monitoring and symptomatic management. Over time, glomus tumors may become visible or at least detectable on MRI.
Radiologists have a particularly difficult time diagnosing glomus tumors on MRI when there are pathologically or anatomically atypical features, no bone erosion and no report of the characteristic symptoms. During consultations with patients, it's important to communicate any suspicion of a glomus tumor and ask about the symptom triad.
Although not an original aim of this study, in the personal opinion of the corresponding author, an MRI may be utilized not simply to make a diagnosis in situations outlined above, but it may also help in defining the size of the lesion and its margins for complete extirpation.
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