| Introduction |
 A painless, benign, slow-growing soft tissue tumor that often occurs in the hand
- occurs months to years after a traumatic event
- Epidemiology
- incidence
- third most common hand tumor
- demographics
- more common in men than women
- occurs in the third to fourth decade
- location
- the distal phalanx is commonly involved
- Pathophysiology
- results from a penetrating injury that drives keratinizing epithelium into subcutaneous tissues or bone
- cells grow slowly to produce an epithelial cell-lined cyst filled with keratin
- Prognosis
- excision is curative
- malignant transformation has not been reported
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| Presentation |
- Symptoms
- painless mass, most commonly occurring in the fingertip
- although less common, erythematous, painful lesions have been reported
- Physical exam
- inspection & palpation
- flesh-colored, yellow, or white in appearance
- well-circumscribed, firm, slightly mobile lesions
- lesions are firmer than ganglion cysts and do not transilluminate
- often superficial and tethered to overlying skin
- range of motion
- there may be loss of ROM when lesions are large and occur near IP joints
- neurovascular exam
- sensory deficits may be evident with 2-point discrimination testing secondary to digital nerve compression
|
| Imaging |
- Radiographs
- recommended views
- AP, lateral, and oblique views of the involved digit or hand
- findings
- soft tissue mass may be evident
- a lytic lesion of the distal phalanx may be present if the cyst erodes into bone
- may mimic a malignant or infectious process
|
| Studies |
- Biopsy
- indications
- should be considered before surgical excision to rule out neoplasm or infection if a lytic bony lesion is present in the distal phalanx
- Histology
- gross appearance
- cysts contain a thick, white keratinous material
- characteristic findings
- cysts filled with keratin and lined with epithelial cells
|
| Differential |
- Tophaceous gout
- Foreign body granuloma
- Sebaceous cyst
- Giant cell tumor
- Ganglion cyst
- Enchondroma
- Glomus tumor
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| Treatment |
- Nonoperative
- Operative
- marginal excision
- indications
- diagnosis of epidermal inclusion cyst
- painful lesions
- loss of function
- cosmetic concerns
- technique
- careful dissection to remove the entire capsule
- local curettage and bone graft may be required for lesions eroding bone
- amputation is an alternative with advanced bony destruction in rare circumstances
- outcomes
- marginal excision is curative
- low recurrence rate
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| Complications |
- Wound complications
- Infection
- Digital neurapraxia
- Recurrence
- recurrence rate is low even with bony involvement
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