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Age / Sex : /
Age / Sex : 22 / F
Chief complaint : A palpable mass, left thumb
1) What is your impression?
Two weeks later, you can see the final diagnosis with a brief discussion of this case.
* Send Application Answers to Ja-Young Choi, MD ([email protected]) *
Courtesy : Yun Sun Choi, MD, Eulji Hospital, Eulji University School of Medicine
Diagnosis: glomus tumor
Discussion
Findings:
There is a relatively well defined nodule in the lateral nail bed. It has led to the erosion of the dorsal cortex of the distal phalanx. The signal of the mass is low on T1-weighted image, high on T2-weighted image and proton FSE image. The mass shows a strong enhancement on post-contrast T1-weighted image.
Differential Diagnosis:
1. Angioma
2. Mucoid cyst
3. Subungal extraskeletal chondroma
Diagnosis: Glomus tumor
Discussion:
A glomus tumor arises from glomus bodies, which are present throughout the body in the deepest layer of the dermis and are highly concentrated in tips of the digits, particulary beneath the nails. It leads to prominent symptoms that appear out of proportion to the size of the lesion (usually less than 1 cm). Plain radiography is not sensitive, and a bony erosion of the distal phalanx, similar to that seen with epidermal inclusion cyst, is seen in less than of 20% of cases. Ultrasound shows hypoechoic masses, doppler hypersignal in the tumor. MR imaging is helpful in the diagnosis, depicting the tumors in 68% of cases. In 1924, Masson described several histologic variants. Histologic composition has no prognostic significance. However, the MR signal characteristics of a glomus tumor depend on its histologic composition. Three main types are generally seen. The vascular type has high signal intensity on T2-weighted image and a very strong enhancement after contrast injection. The cellular or solid type may be difficult to detect with MR imaging. Its signal is close to that of the normal dermis of the nail bed on all sequences. Injection of the contrast is of little use. The mucoid type has very high signal intensity on T2-weighted image and mild enhancement after contrast injection. Most tumors are composed of a mixture of the various types. The tumor margins are usually well defined by a peripheral pseudocapsule. This capsule is a reactive response of the surrounding connective tissue and demonstrates very low signal intensity on all sequences. Multiple glomus tumors may arise in the hand or in the same finger tip, and some cases have been reported in association with neurofibromatosis type I. In most cases, the tumor is located in the subungal area, in the supporting tissue of the nail bed or the matrix. This lesion is usually deep, close to the periosteum of the underlying phalanx. Occasionally the tumor is located in the pulp or the posterior nail fold. A glomus tumor must be differentiated from an angioma, a mucoid cyst and a subungal extraskeletal chondoma. An angioma has the same signal intensity features as a glomus tumor and more superficial location. A mucoid cyst shows the lack of contrast enhancement. A subungal extraskeletal chondoma may mimic a glomus tumor, but the peripheral enhancement pattern is different. The risk of recurrence is definitely high if some tumor tissue is left in situ during surgery or ill-defined lesions. The reported recurrence rate ranges from 12% to 24%.
References:
1. Drape JL, Idy-Peretti I, Goettmann S, Wolfrem-Gabel R, et al. Subungual glomus tumors: evaluation with MR imaging. Radiology 1995;195:507-515.
2. Stoller D. Magnetic resonance imaging in orthopedics and sports medicine, 3rd ed. Philadelphia, Lippincott, 2007
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