What types of cysts can be present on the forearm?

Types of Cysts on the Forearm

The two most common cysts that occur on the forearm are ganglion cysts and epidermoid inclusion cysts, with ganglion cysts being the most frequent soft tissue mass in the hand and wrist region, accounting for 50-70% of all masses identified. 1

Ganglion Cysts

Ganglion cysts are the predominant cystic lesion of the forearm and wrist, presenting as soft tissue swellings that are typically asymptomatic aside from the visible mass itself. 2

Clinical Characteristics

• Most patients present with cosmetic concerns and fear of malignant growth, though these lesions are benign 2
• Additional symptoms may include pain, weakness, or paresthesias when present 2
• The natural history is favorable: 58% of ganglion cysts will resolve spontaneously without intervention 2

Pathophysiology

• Current theories suggest that extra-articular mucin "droplets" coalesce to form the main cyst body, with the cyst wall and pedicle (connecting to nearby synovial joints) forming subsequently 3
• The exact mechanism remains incompletely understood 3

Management Approach

• Watchful waiting is appropriate as first-line management given the high spontaneous resolution rate 3
• Aspiration with or without injection carries a high recurrence rate and is generally ineffective 2, 3
• Surgical excision provides lower recurrence rates but higher complication rates and longer recovery periods 2
• If symptomatic relief is the primary concern, conservative management is preferred; if preventing recurrence is paramount, surgical intervention is indicated 2

Epidermoid Inclusion Cysts

Epidermoid inclusion cysts are the second most common mass presentation in the hand and forearm after ganglion cysts. 4

Clinical Features

• These cysts contain cheesy keratinous material and harbor normal skin flora even when uninflamed 5, 6
• They likely arise from traumatic events that drive epithelial cells into subcutaneous tissues where they survive, proliferate, and produce keratin 4
• When uninflamed, they present as asymptomatic nodules 6

Inflammatory Presentation

• Inflammation occurs as a reaction to cyst wall rupture and extrusion of contents into the dermis, rather than from primary infection 5, 6
• Inflamed cysts present as painful, tender swellings that may mimic abscesses 6

Treatment Protocol

• Effective treatment requires incision, thorough evacuation of contents, probing the cavity to break up loculations, and covering with a dry dressing 5, 6
• Systemic antibiotics are rarely necessary unless complications exist including: multiple lesions, cutaneous gangrene, severely impaired host defenses, extensive surrounding cellulitis, or severe systemic manifestations like high fever 5, 6
• Gram stain and culture are typically unnecessary 5

Important Clinical Distinctions

Dermoid Cysts (Less Common on Forearm)

• These are congenital choristomas containing more complex structures like hair, teeth, and cartilage due to their developmental origin 6
• On ultrasound, they show hyperechoic components with acoustic shadowing, hyperechoic lines and dots, and sometimes fluid-fluid levels 6
• These are anatomically distinct from epidermoid cysts and rarely occur on the forearm

Key Pitfall to Avoid

Do not confuse inflamed epidermoid cysts with true abscesses requiring antibiotics. 5 The inflammation is typically sterile and results from chemical irritation from cyst contents rather than bacterial infection. Simple incision and drainage without antibiotics is usually sufficient unless the specific complications noted above are present.