Glomus Tumor
A subungual glomus tumor is a benign primary neoplasm that arises from the glomus body (Sucquet–Hoyer canal), a specialized arteriovenous anastomosis in the deep dermis of the nail bed that plays a key role in regulating fingertip temperature.
Histologically, the tumor is an abnormal mixed proliferation of three components: smooth muscle–like glomus cells, endothelium-lined vascular channels, and smooth muscle cells.
- Histopathology:
- Glomus cells: Uniform cells with round to oval nuclei and pale eosinophilic cytoplasm, arranged in sheets or clusters around vessel lumina.
- Vascular spaces: Small, dilated capillaries lined by normal endothelial cells and tightly cuffed by several layers of glomus cells.
- Immunohistochemistry (IHC): Tumor cells stain strongly for SMA (smooth muscle actin) and vimentin; the endothelial component is CD31/CD34 positive, while S100 and cytokeratin are negative.
- Why the Pain Is So Characteristic:
- The tumor sits in a space that cannot expand, trapped between the rigid nail plate above and the distal phalanx below. Any change in temperature (cold in particular) or even light pressure makes the glomus cells contract forcefully.
- That contraction instantly raises the pressure inside the tumor and squeezes the surrounding web of pain-sensing nerve fibers (nociceptors), which fire sharp pain signals straight up to the cerebral cortex.
Glomus tumors are tiny (usually only 2–5 mm) and hidden deep beneath the nail plate, so they are easy to miss on a routine examination. Many patients live with stabbing pain for years and are misdiagnosed with "peripheral neuropathy," "paronychia," or a "sensory disorder." Combining the characteristic clinical tests (Love, Hildreth, and cold test) with high-frequency ultrasound is the standard approach for pinpointing the lesion to the millimeter before microsurgery.
Clinical Features and Specific Diagnostic Tests
Glomus tumors are almost always solitary and found on the fingers (90% of cases occur under the nail), and they are more common in women.
The Classic Clinical Triad
- Localized paroxysmal pain: Pain comes on spontaneously or with a light knock at one fixed point under the nail. It is sharp and needle-like and can shoot along the finger up to the wrist.
- Cold hypersensitivity: Severe pain flares when the finger meets cold water or cold air, or when the seasons change.
- Point tenderness: Patients can often show the exact center of the pain under the nail with the tip of a pencil.
Diagnostic Clinical Tests
- Love's pinpoint test (+): A fine probe (1 mm) or the head of a sterile pin is pressed gently on one point of the nail plate after another. The patient jerks away in pain when the probe lands directly over the tumor.
- Hildreth's test (+): A tourniquet is tightened at the base of the finger to stop blood flow, and Love's test is repeated ➔ the pain disappears completely. When the tourniquet is released, the sharp pain returns at once as blood rushes back into the tumor.
- Transillumination test: A high-intensity LED light shone through the nail plate reveals a sharply defined, dark red-purple spot.
Digital Onychoscopy (Nail Dermoscopy) Findings
- Dorsal view:
- A red-purple or bluish macule hidden beneath the nail plate.
- Localized splinter hemorrhages.
- The nail plate over the tumor may bulge slightly or show a longitudinal ridge where the tumor presses up from below.
Telling Glomus Tumors Apart From Other Common Subungual Lesions
| Glomus Tumor | Onychopapilloma | Myxoid Pseudocyst |
|---|---|---|
| Neuromyoarterial tumor of the glomus body | Papilloma of the distal nail bed epithelium | Mucin degeneration / herniated joint fluid |
| INTENSE SHARP PAIN, cold-sensitive | Painless / mild pain | Mild tightness |
| Love/Hildreth tests + | Love/Hildreth tests − | Love/Hildreth tests − |
| Red-purple spot hidden under the nail | Longitudinal red band + keratotic plug at the free edge | Translucent swelling of the proximal nail fold |
| Well-defined hypoechoic mass with Doppler flow | Localized nail bed hyperkeratosis | Well-defined anechoic fluid sac |
Diagnosis, Imaging, and Microsurgical Treatment at Haute-Derma
At Haute-Derma, patients with subungual glomus tumors are treated according to the Haute-Derma Subungual Glomus Tumor Protocol, which pairs nail bed–sparing microsurgical excision with nail matrix reconstruction:
Imaging to Map Tumor Position and Size
- High-frequency ultrasound: Shows a well-defined hypoechoic mass in the nail bed. On color Doppler, the tumor displays strongly increased blood flow (hypervascularity).
- Magnetic resonance imaging (high-resolution T2-weighted finger MRI): When the tumor is very small (<2 mm), MRI shows low signal on T1 and a markedly hyperintense signal on T2, with rapid contrast enhancement.
Individualized Microsurgical Approach
- A digital nerve block is given with 2% lidocaine without epinephrine, and a tourniquet at the base of the finger keeps the surgical field completely bloodless.
- Transungual approach (for tumors in the center of the nail bed): A window is cut in the nail plate directly over the tumor, and the nail bed is gently lifted to expose the well-circumscribed red-purple tumor.
- Lateral subperiosteal approach (for tumors at the lateral edge or proximal nail fold): An incision along the lateral nail fold allows dissection beneath the periosteum, leaving the entire nail plate intact.
Complete Microsurgical Excision and Nail Bed Repair
- Working under microsurgical magnification, the surgeon shells out the red-purple tumor intact from its bed in the nail bed or from the pressure defect in the distal phalanx.
- Flat microsurgical nail bed repair: The edges of the nail bed defect are brought back together with ultra-fine 8-0 sutures (absorbable Monocryl or Ethilon). This is the key step in preventing a deformed or split nail after surgery.
- The original nail plate (or a silicone sheet) is put back in place as a splint that holds the shape of the nail bed for 2–3 weeks.
Postoperative Care and Histopathology
- The specimen is sent for H&E staining and SMA immunohistochemistry (+) to confirm the diagnosis.
- The site is covered with an HPCH polymer biological film, combined with LLLT (630 nm) twice a week, to support healing and help the new nail plate grow back smooth and even.
