= rare small benign hamartoma of digits

Origin: cells derived from neuromyoarterial apparatus (responsible for thermoregulation in skin)

Glomus body = encapsulated oval organ of 300 µm length; located in reticular dermis (= deepest layer of skin); concentrated in tips of digits (93–501/cm²)

Components: afferent arteriole, tortuous arteriovenous anastomosis with an anastomotic vessel (= Sucquet-Hoyer canal lined by endothelium + surrounded by smooth muscle fibers), system of collecting veins, intraglomerular neurovascular reticulum + capsule

Histo: endothelium-lined vascular spaces surrounded by masses of round epitheloid cells with tendency toward spindle form

Subtypes: (a) vascular (b) myxoid (c) solid form

Prevalence: 1–5% of soft-tissue tumors of hand

Age: mostly in 4^th–5^th decade; M÷F = 1÷1

Location: highly concentrated in digits (75% of glomus tumors)

• Account for 1.0–4.5% of all hand tumors

Site: subungual space (65%); multiple tumors in 2.3%

• intense joint tenderness + excruciating pain provoked by temperature sensitivity + mild trauma (on average 4–7 years duration prior to diagnosis); ± nail ridging + discoloration
• Love test = eliciting pain by applying precise pressure with a pencil tip
• Hildreth sign = disappearance of pain after application of a tourniquet proximally on arm (PATHOGNOMONIC)
• SUBUNGUAL GLOMUS TUMOR
  • increased distance between dorsum of phalanx + underside of nail (25%)
  • extrinsic pressure erosion of adjacent bone (14–25–65%), often with sclerotic border
  
  US:
  • small hypoechoic solid tumor (>3 mm detectable)
  • ±erosion of underlying phalangeal bone
  • SPECIFIC hypervascularity on color Doppler
  
  MR:
  • lesion of intermediate / low SI on T1WI
  • homogeneously T2-hyperintense lesion (detectable if >2 mm in diameter)
  • strong enhancement during arterial phase
  • tumor blush during delayed phase on CEMR images
• GLOMUS TUMOR OF BONE occasionally within bone
  • resembles enchondroma

DDx:

1. Mucoid cyst (painless, in proximal nail fold, communicating with DIP joint, associated with osteoarthritis)
2. Angioma (more superficially located)