Glomus tumor of the nail unit.

Glomus tumor is a benign tumor arising from the neuromyoarterial plexus concentrated beneath the nail. This plexus is an arteriovenous anastomosis functioning without the intermediary capillary bed. Etiology is not exactly known. It is debilitating to the patient because of the chronicity of symptoms and lack of proper investigation which will help in identifying the tumor at an early stage. We report a case of glomus tumor situated in the proximal nail fold region and causing longitudinal splitting of nail.

Introduction

Glomus tumor was first described by Wood as early as 1821, but the characteristic histological description was given by Masson.[1] These relatively rare tumors account for 5.5% of nail unit tumors.[2] They are mostly located in the subungual region but occur less frequently in other nail unit region and extradigital sites. Characteristic triad of symptoms of temperature sensitivity, severe pain and localized tenderness can be noted in 63-100% of the patients.[1]

Case Report

A 36-year-old female was referred from surgery department, with history of pain in the left thumb since 10 years. Initially, the pain was vague in nature and later became intense. She also reported exacerbations of symptoms during rainy and winter seasons. Even a minor trauma used to provoke severe bout of pain. She noticed splitting of nail 3 years back, which gradually progressed to involve the whole length of nail. No other significant medical or surgical history was recorded. On examination, there was a small swelling with indistinct margins just behind the proximal nail fold. It was extremely tender to touch. There was also longitudinal split in the nail which was extending from the free end of the nail plate to the proximal nail fold [Figures 1 and 2]. No color changes either in the nail plate or in the proximal nail fold were noted. Love's test was positive and Hildreth's test was negative. Immersion of involved thumb in cold water induced pain, indicating positive cold sensitivity. Patient was investigated. Her routine blood and urine investigations were within normal limits. Radiographic examination of the patient did not reveal any abnormalities. Surgical exploration was done under digital nerve block and tourniquet. Intraoperatively, a semitranslucent mass of 2 mm × 3 mm size was found. It was excised and sent for histopathological examination. Histopathology revealed clusters of monomorphous tumor cells set in a hyalinized stroma. These tumor cells had sharply punched out round to oval nucleus and well-defined borders. There were some dilated vessels with clusters of tumor cells in their walls [Figure 3].

Figure 1

Fullness in posterior nail fold region

Figure 2

Glomus tumor during exploration

Figure 3

Tumor cells invading vessel wall (magnification ×10)

Discussion

Glomus tumors most commonly occur in the digits. They account for 1-5% of soft tissue tumors of hand.[3] Subungual location is the preferred site for digital glomus tumor, but can occur in other areas also. In our patient, the site involved was in posterior nail fold region, which is a rare occurrence. Drape et al. reported the same in only one of his 28 glomus tumor patients evaluated by magnetic resonance (MR) imaging. The most common site in his study was the reticular dermis of nail bed in rest of the patients.[3] Pain is the most common presentation of glomus tumor. Our patient had the classical triad of symptoms - temperature sensitivity, severe pain and localized tenderness. This can be noted in 63-100% of the patients.[1] Bhaskaranand and Navadgi reviewed different clinical tests to diagnose glomus tumors and opined that cold sensitivity test is the most accurate test to diagnose glomus tumors.[4] Our patient also had positive cold sensitivity, confirming their view. Positive cold sensitivity is also reported by Vasisht et al. in 84% of their patients.[5] Erythronychia and distal onycholysis were seen in all the glomus tumor patients studied by Dominguez-Charit et al.[2] Nail deformity may result because of pressure effect of glomus tumor on nail matrix. Drape et al. noticed this compressive effect of glomus tumor on nail matrix by MR imaging.[3] Nail splitting was observed in our patient. No color change of nail plate was observed in our patient. Vasisht et al. noted the same in 76% of patients and only 24% of his patients had blue blush of nail in their study.[5] Radiographic examination was inconclusive in our patient and the same was reported by Bhaskaranand and Navadgi in their study.[4]

Complete surgical excision is the treatment of choice. Use of High Resolution Magnetic Resonance Imaging (HR-MRI) and High Variable Frequency Ultrasound (HVFUS) in preoperative assessment will help in the outcome of surgical treatment. Bhaskaranand and Navadgi employed the use of double tourniquet, one at the mid arm and the other at the base of digit, for better visualization of the tumor during exploration.[4] Surgical exploration was done and tumor was removed in our patient. Patient was free of symptoms during the postoperative period. Patient was followed up and it was noticed that she had recurrence of pain after 6 months. She also developed nail ridging after 1 year. This was probably because of incomplete removal of the tumor. Small size and difficulty in locating the tumor by traditional methods were the contributory factors.

MRI and HVFUS can help to diagnose and locate the tumor accurately. But due to their high cost, glomus tumors continue to cause diagnostic difficulty to the treating physician because of their small size and lack of simple cost-effective investigation.