Are You Confident of the Diagnosis?

What you should be alert for in the history

The classic presentation of a mucous cyst involves a 60-year-old female with a mass on the dorsal aspect of her distal phalanx that she first noted several months ago (rarely are they in multiple locations). Associated with the slowly enlarging mass is a longitudinal groove of the nail that she finds cosmetically unappealing.

On physical examination, the skin is noted to be thin and appears as if it might rupture. She has full range of motion of the digit with slight discomfort. Radiographs reveal a narrowed distal interphalangeal joint space with mild osteoarthritis (OA) and osteophyte formation.

From this presentation the observant historian can glean several key characteristics of mucous cysts. Patients often describe a mass that has been slowly progressing over months to years and has drained a clear mucous/gelatinous fluid. Mild discomfort may be reported that is secondary to an underlying osteoarthritis. A history of precipitating trauma is absent. Patients generally present for cosmetic reasons or a concern for malignancy.

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Characteristic findings on physical examination

Physical examination findings depend on the specific location of the cyst. The cyst is often a solitary, round to oval, dome-shaped, skin-colored to translucent papule or papulonodule that ranges in size from 1 to 10mm. The overlying epidermis may be thinned, thickened or even verrucous. They are most commonly located on the dorsal or dorsolateral surface of a finger, with the middle finger most commonly affected. They occur less commonly on the toes.

The cyst may appear near the distal interphalangeal joint (DIPJ), between this joint and the proximal nail fold (PNF), superficial to the nail matrix within the PNF, deep to the nail matrix (subungual location), lateral to the DIPJ, or within the distal digit pulp. Characteristic nail changes depend on cyst location and include a longitudinal groove of the nail plate distal to the cyst, red or blue lunula, and decreased nail integrity when in the subungual location.

Other less common nail changes include concave canaliform dystrophy, washboard transverse lines, and longitudinal groove with beaded ridges. In many patients evidence of OA can be seen including Heberden’s nodes. Uncommon presentations include multiple cysts on the same digit or multiple digits, herpetiform configuration, and near the knee joint (Figure 1).

Expected results of diagnostic studies

Imaging of mucous cysts is not necessary for diagnosis, but may be obtained if planning surgical intervention. Radiographs are likely to show osteoarthritis of the DIPJ with dorsal osteophyte formation (Figure 2).

When needed, histologic examination reveals one of two types of pseudocyst; neither have a true cyst wall. The first is similar to focal mucinosis with an ill-defined area of mucinous material containing spindled to stellate fibroblasts within the superficial dermis. Over time it develops into a cyst-like space filled with hyaluronic acid and may cause attenuation of the overlying epidermis associated with peripheral acanthosis.

The second type is more representative of a ganglion with a large dermal cavity surrounded by compressed collagen forming a pseudocapsule. The latter lesion tends to be deeper in the dermis.

Diagnosis confirmation

The differential diagnosis of mucous cyst includes Heberden’s node, epidermal inclusion cyst, giant cell tumor of the tendon sheath, foreign body granuloma and rheumatoid nodule.

Heberden’s nodes, also located in the DIPJ and associated with OA, can be distinguished from mucous cysts by the presence of a firm, non-tender, subcutaneous swelling that can deviate the distal phalanx.

Epidermal inclusion cysts may have a punctum with white cheesy material rather than viscous fluid and generally present on the palm or fingertips of people with occupations that predispose them to penetrating injuries in which epidermal cells become implanted in the dermis.

Giant cell tumors of the tendon sheath consist of mononuclear cells and polyclonal giant cells that present as firm multi-lobulated subcutaneous masses and would not transilluminate.

Hyperostosis is differentiated via plain radiographs. Glomus tumor would be painful when exposed to cold, and may have color change to the lunula. Neurofibroma is differentiated by visual inspection during surgery or histology. Fibrokeratoma would have more surface contour than the typical mucous cyst and would be differentiated on histologic examination if there was a question.

Who is at Risk for Developing this Disease?

Mucous cysts are a subtype of ganglion cysts, which are the most common benign masses of the hand and digits. Mucous cysts are thought to comprise 10% to 15% of ganglion cysts in the hand. Females are affected more often than males, with the common age at diagnosis being 50 to 70 years. The major risk factor for mucous cyst formation is degenerative changes in the distal interphalangeal joint associated with OA.

What is the Cause of the Disease?

The etiology of mucous cysts has remained controversial and multiple theories have been proposed. The currently accepted theory holds that stress on the capsular and ligamentous joint structures produce mucin that dissects through these structures, forming ducts that eventually coalesce into cysts. The osteoarthritic joint may have a weak capsule and rupture into the surrounding tissue. Cystic fluid, composed of glucosamine, albumin, globulin and hyaluronic acid, arises in the joint and communicates through a stalk to the main cyst. These cysts lack a cellular epithelial lining and thus are not true cysts.

Systemic Implications and Complications

Mucous cysts are benign masses associated with OA of the DIPJ. Because of their thin, atrophic skin coverage, they are at risk for infection which can quickly progress to septic arthritis of the DIPJ (Figure 3). In rare cases of delayed diagnosis, this can progress to severe infection of the digit. There are rare cases of multiple cysts in patients with juvenile rheumatoid arthritis and systemic sclerosis.

Treatment Options

Treatment options are summarized in Table I.

Table I.
Surgical Medical
Joint debridement without formal cyst excision Aspiration
Cyst excision with routine osteophyte excision with or without pedicle ligation Intralesional corticosteroid injection
Cyst excision without osteophyte excision Intralesional sclerosing agent injection

Other options include cryotherapy, carbon dioxide or laser ablation, curettage.

Optimal Therapeutic Approach for this Disease

If the patient is asymptomatic and no nail dystrophy is present or dystrophy is not bothersome to the patient, observation is reasonable. Inquire about Raynaud’s. If present, do not consider cryoptherapy a viable option and be cautious with surgical treatments. Needling is okay. If systemic sclerosis is present, be cautious with surgical treatments. Needling is okay.

Many options are possible and each treatment essentially scars the area, inhibiting accumulation of the cyst. Surgical treatment offers the lowest recurrence rate and can be safely accomplished with few complications. The potential risks of surgical excision include radial or ulnar deviation of the DIPJ, infection, joint stiffness and nail plate deformity. Joint instability can be reduced by careful dissection of the extensor tendon and collateral ligaments. Obtaining proper hemostasis will decrease the risk of wound complications and infections. Avoiding the germinal matrix will reduce the rate of a postoperative nail plate deformity.

Furthermore, proper excision of the cyst will likely improve a preoperative nail deformity. Significant skin defects can be easily closed with local tissue flaps. These risks are easily outweighed by the improved success rate when compared to medical treatment.

Surgical excision is unlikely to prevent recurrence unless the stalk of the mucous cyst is removed (Figure 4). Injection of methylene blue dye that has been mixed with hydrogen peroxide and diluted with saline or lidocaine into the volar DIPJ has been shown to help track the stalk of the cyst and reveal satellite cysts. Improvements in magnetic resonance technologies have assisted in preoperative location of the stalk and satellite cysts in T2-weighted images, but are not indicated for routine management of mucous cysts.

Mucous cyst excision can be performed under digital block anesthesia in the operating room; however, the surgical technique can vary. Gingrass, in a prospective study of 20 cysts with nail deformities, proposed joint debridement without formal cyst excision. The author drained the cyst when the stalk was dissected from the joint and left the cyst wall intact. The rationale for the approach notes that excision of the cyst wall can potentially injure the germinal matrix and cause a nail deformity.

No recurrences were reported at a mean 3- year follow-up, and 18 patients had a complete resolution of the nail deformity. When compared with a previous study by the same author, this reduced the rate of residual nail deformity from 36% to 10%.

Rizzo treated 54 patients with cyst and osteophyte excision. At a minimum 2-year follow-up, no recurrences were reported and nail deformities resolved in 25 of 31 patients without a new occurrence. Similar results were reported by Fritz, who excised 86 cysts and osteophytes. In this study, with a mean 2.6-year follow-up, three of 86 cysts recurred. Nail deformities resolved in 60% of patients but 7% were left with a new postoperative nail deformity.

In a study of cyst excision without osteophyte excision, seven of 25 patients developed a recurrence. Similar results were reported in another study demonstrating recurrence in five of 18 patients.

Aspiration and corticosteroid injection was evaluated by the previously cited Rizzo. The author noted a 40% recurrence rate in 800 cysts that were followed for a minimum of 2 years. Another study reported a 36% recurrence rate with steroid injection. One could use an 18- to 22-gauge needle; drain the contents and then leave the cyst with or without pressure bandage to theoretically prevent the area from filling back up.

In our experience, the best results with the lowest rates of recurrence have been with cyst excision and concurrent osteophyte debridement.

Other options include ablative lasers with endpoints as seen in surgical treatments, but may be more difficult to delineate due to the heat destruction of tissue. Cryotherapy would be nonselective destruction of the area with caution needed due to the unknown depth of freezing. Neither of these techniques is recommended for routine treatment of digital mucous cysts.

Patient Management

Patients should be advised that mucous cysts are benign lesions and surgical excision is an elective procedure. Additionally, patients should be cautioned regarding the limitations of treatment. Aspiration is generally not recommended, as recurrence rates are high and the risk of bacterial contamination exists. Regardless of the treatment modality, recurrence and/or development of a new lesion in the same digit may occur. Complete pain relief may not be achieved due to the underlying arthritic joint.

Unusual Clinical Scenarios to Consider in Patient Management

In the setting of mucous cyst infection, broad-spectrum antibiotics should be started immediately. Consultation with a hand surgeon is critical as cyst infection can rapidly progress to septic arthritis of the DIPJ, with potential dire consequences for future digit function. In extreme cases of infection with digital edema, fasciotomy of the forearm may be necessary to maintain vascularity of the digit (Figure 5).

What is the Evidence?

Nahra, ME, Bucchieri, JS. “Ganglion cysts and other tumor-related conditions of the hand and wrist”. Hand Clin. vol. 20. 2004. pp. 249-60. (A comprehensive review of the variety of ganglion cysts of the hand and wrist.)

Budoff, JE. “Mucous cysts”. J Hand Surg. vol. 35A. 2010. pp. 828-30. (A review of the current methods for the treatment of mucous cysts.)

Newmeyer, WL, Kilgore, ES, Graham, WP. “Mucous cysts: The dorsal distal interphalangeal joint ganglion”. Plastic Reconstruct Surg. vol. 53. 1974. pp. 313-5. (The original description of the Newmeyer test for locating mucous cyst pedicles with methylene blue injection.)

Rizzo, M, Beckenbaugh, R. “Treatment of mucus cysts of the fingers: Review of 134 cases with minimum 2 year follow-up”. J Hand Surg. vol. 28A. 2003. pp. 519-24. (A comparison study of aspiration and injection versus surgical excision in 80 and 54 patients respectively.)

Constant, E, Royer, JR, Pollard, RJ. “Mucus cysts of the fingers”. Plastic Reconstruct Surg. vol. 43. 1969. pp. 241-6. (A review of the incidence, epidemiology, clinical characteristics and pathogenesis of mucous cysts.)

Drapé, JL, Idy-Peretti, I, Goettmann, S, Salon, A, Abimelec, P, Guérin-Surville, H. “MR imaging of digital mucoid cysts”. Radiology. vol. 200. 1996. pp. 531-6. (An assessment of MR imaging in the diagnosis and clarification of mucous cysts.)

Crawford, RJ. “Mucous cyst of the distal interphalangeal joint: Treatment by simple excision or excision and rotation flap”. J Hand Surg (Br). vol. 15B. 1990. pp. 113-4. (A single institution’s review of the surgical excision of mucous cysts and the recurrence rate.)

Kasdan, ML, Stallings, SP, Leis, VM, Wolens, D. “Outcome of surgically treated mucous cysts of the hand”. J Hand Surg. vol. 19A. 1994. pp. 504-7. (A single institution review of the surgical excision of mucous cysts and associated complications.)