According to the Mayo Clinic, a glomus tumor is a rare benign tumor that accounts for 1.6% of soft tissue tumors occurring in limbs and about 2% of hand tumors. It is reported that 25–65% of glomus tumors occur in the subungual region [
5,
6]. In addition to developing in the hands, glomus tumors may occur in all other areas of the body with a normal glomus body, and their occurrence has been reported even in areas without a normal glomus body. The conversion to a malignant tumor is reported to be very rare, less than about 1% [
7].
Typical symptoms of glomus tumors include pain, tenderness, and cold hypersensitivity. However, because all of these three symptoms are not observed simultaneously in all glomus tumors, the symptoms are not that helpful for making a diagnosis [
5]. In addition to the above-described symptoms, a number of other ones, including tingling pain, causalgia, and radiating pain, may occur; therefore, it is important to suspect glomus tumors in patients who complain of these symptoms. In our patient, the main symptom he reported was only tenderness among the three symptoms of glomus tumors, and the tumor was located not in the hands, which the glomus tumor often affects, but in the forearm. Because the tumor size was very small, and because it presented without skin discoloration, it was difficult to suspect a glomus tumor until the biopsy result was identified. Also, the patient had not visited the hospital when he first noticed his symptoms, because he had no particular pain unless the lesion was pressed, and he had been careful not to press the lesion to prevent pain in his everyday life. He was diagnosed 8 years after the first symptom occurrence.
It is important for early diagnosis and treatment to suspect a glomus tumor in patients who complain of the above-described symptoms in areas other than the hands. Generally, a glomus tumor is reported to be treated well with complete resection, and the rate of recurrence is reported to be under 10%. Recurrence is caused by incomplete resection [
2]. In addition, the possibilities of malignant change and distant metastasis have also been reported, implying that continuous follow-up is needed. Because deterioration of a patient’s quality of life and the risk of complications are expected owing to such properties of a glomus tumor, it is important to suspect the disease early and initiate proper treatment.
Most of the conventional radiologic findings on our patient’s imaging examinations were normal, but cortical bone breakage or cystic bone breakage caused by the pressure of the tumor may be seen in some patients. If the clinical symptom of cold hypersensitivity does not exist when the lesion occurs in areas other than those the lesion generally affects, it will be even more difficult to suspect a glomus tumor. In that situation, a glomus tumor must be differentiated from other vascular tumors, such as hemangiomas or vascular malformations, as we did in our patient. Indeed, the term
hemangioma was originally used to describe any vascular tumor-like structure, whether it was present at or around birth or appeared later in life. The classifications and terminology used for various vascular lesions can be very confusing, despite the fact that a biological classification was first published in 1982 by Mulliken and Glowacki [
8]. On ultrasounds, vascular tumors such as hemangiomas or vascular malformations, hypoechoic or hyperechoic patterns may occur, posterior acoustic shadowing can be observed, and ill-defined margins with adjacent tissues may occur frequently. The blood flow rate in vascular tumors occurs in various ways, but a hypervascular tumor pattern may been seen in some cases. It may be observed that the blood flow of vascular tumors in a subcutaneous fat layer decreases owing to the pressure on the vein inside the tumor but increases again when pressure is released. Detection of this symptom helps in making the correct diagnosis [
9]. According to Mulliken and Glowacki [
8], however, hemangiomas are characterized clinically by appearing at or shortly after birth. A rapid proliferative phase occurs during the first 9–12 months of life, followed by an involution phase that may be completed by 3–5 years of age; but this phase can last up to 12 years of age. In addition, vascular malformations that are present since birth tend to grow proportionately with the patient’s age. Therefore, we considered vascular tumors such as a hemangioma or a vascular malformation to be unlikely in our patient. On the contrary, a glomus tumor shows hypoechoic findings and posterior acoustic enhancement on ultrasonograms. Despite its very small size, usually less than 1cm, its boundary with adjacent tissues is clear. With a glomus tumor around cortical bone, erosion or breakage of the cortical bone may be observed. Also, in Doppler sonography, a glomus tumor shows hypervascularity, which is accompanied by severe pain rather than a change of shape due to pressure [
8]. Thus, in patients with such findings, it is of great help to make a diagnosis of a glomus tumor. Ultrasonography is useful in differentiating the tumor and identifying its location and size, but it needs careful attention because it may appear negative for lesions as small as 2mm. In such patients, MRI may be helpful. For glomus tumors, T1-weighted sequences show intermediate or low signal intensity, similar in degree to muscle; T2-weighted sequences show high signal intensity; and contrast-enhanced images shows high signal intensity [
4]. In our patient, no specific findings were observed on conventional radiographs; the boundary with surrounding tissues was found to be clear on ultrasound; the proliferation of blood vessels was observed as a hypoechoic mass located inside the subcutaneous fat layer; and increased blood flow was visualized by Doppler sonography. MRI could not be performed in our patient, owing to his expressed financial reasons. Considering that the only clinical symptom was tenderness and the tumor was located in an area other than the hands, the typical occurrence site for glomus tumor, it was difficult to differentiate a hemangioma from a glomus tumor. However, on the basis of our ultrasound findings, a glomus tumor rather than a hemangioma was suspected, and a surgical resection was performed. The diagnosis of a glomus tumor was ultimately made on the basis of post-surgical pathologic findings. After complete resection, the patient fully recovered without additional treatment, and his pre-operative clinical symptoms disappeared completely immediately after surgery and during follow-up.