Digital Mucous Cyst Treatment
Primary Care Visit Report
A 59-year-old female with no past medical history presented with a lesion on the pinky finger of her right hand. She first noticed the sore about 2–3 months prior. It was not painful, but it had started to distort her fingernail.
Vitals were normal. On exam, on the right hand fifth digit, just proximal to the nail bed, there was a 2 mm soft, non-tender, fluctuant mass with nail deformation.
This was treated as a digital mucous cyst , and the patient was referred to dermatology for surgical excision.
Discussion from Dermatology Clinic
Differential Dx
Favored Dx
Digital mucous cyst (DMC) is the favored diagnosis. The mass’s presentation as nontender and fluctuant, its persistence without change over 2 months, and its location on the proximal nail fold are all features consistent with DMC.
Overview
Digital mucous cysts, sometimes referred to as mucoid or myxoid cysts , are benign cysts of the fingers and toes. They lack epithelial lining, making them pseudocysts . They typically appear between the fourth and seventh decade, and are twice as likely to occur in women than men [ 1 ]. They are thought to arise from mucoid degeneration of connective tissue [ 2 ].
Two distinct forms have been described: myxomatous and ganglion type DMCs [ 1 , 3 – 6 ]. The myxomatous type occurs due to metabolic changes in fi broblasts that lead to overproduction of hyaluronic acid, which then gets trapped, creates a cystic space and leads to a DMC. These are not connected directly to the adjacent joint. Ganglion type DMCs are associated with degenerative joint disease and occur more frequently in people with osteoarthritis. Ganglion type cysts are anchored directly to the affected joint (usually the distal interphalangeal joint ) via a pedicle, and are fi lled with synovial fluid [ 3 – 5 ].
The two types are clinically indistinguishable, and a definitive diagnosis can only be made during surgery if a pedicle is observed, or by histopathology.
Presentation
Digital mucous cysts are translucent, round, dome-shaped lesions that appear on lateral or dorsal aspects of distal interphalangeal joints , or on the proximal nail folds of digits. They most frequently appear as solitary lesions; however, there have been a few reports of multiple DMCs [ 3 ]. They typically appear on fingers, although they also sometimes appear on toes [ 2 ]. DMCs tend to be under 1 cm in size. They are usually asymptomatic. They may sometimes discharge spontaneously, or cause reduced range of motion, pressure to the nail bed, nail deformities, and pain, espe-cially as the cysts enlarge [ 1 , 3 ].
Workup
Some of the differential diagnoses can be ruled out based on history. Acral fi bro-keratomas are usually preceded by local trauma; tumors (GCTTS, histiocytoma) would exhibit rapid growth.
Digital mucous cysts tend to be compressible, can be transilluminated , and express clear or yellow viscous, jelly-like contents when incised. White structures appear on compression, consistent with increased collagen [ 2 , 7 ]. If diagnosis is unclear, imaging studies (plain X-ray, MRI, CT, ultrasound) may be done to determine the nature of the growth.
If a biopsy is performed to rule out malignancy, histopathology of mucous cyst would reveal a cystic space with mucinous content, increased fi broblasts in the dermis, and no apparent lining of the cyst wall [ 3 ].
Treatment
DMCs are benign and may not require treatment. Asymptomatic cysts can be monitored. Some digital mucous cysts may spontaneously resolve. If patients are bothered by cosmetic appearance, they experience discomfort, or the DMC is causing nail deformity or functional impairment cysts may be treated. Treatment options include incision and drainage, intralesional steroids (e.g., triamcinolone acetonide 5–10 mg/ml), sclerotherapy (e.g., 1 % sodium tetradecyl sulfate), cryosurgery , elec-trodesiccation , CO 2 laser, and surgical excision. Of these the most effective is surgical excision, with cure rates up to 100 % [ 1 , 4 – 6 , 8 , 9 ].
A conservative approach of incision and drainage followed by steroid injection is favored. This may be done in a primary care setting [ 6 ]. I&D usually requires several treatments as fluid tends to re-accumulate, and leads to cure rates of up to 72 % [ 5 , 6 ]. Steroid injection alone is associated with high recurrence rates [ 6 ]. Cryosurgery has a 56–86 % cure rate [ 5 ]. It requires unroofi ng and draining the cyst, and freezing down to the cyst base. Frost should be maintained for about 10 s, which can be achieved by spraying continuously for about 4–5 s, then allowing it to thaw. This freeze-thaw cycle should be repeated 2–3 times per visit. Patients desiring treatment by sclerotherapy, electrodesiccation, CO 2 laser, or surgery should be referred to dermatology or hand surgery.
Follow-Up
The literature on DMCs suggests a possible risk of infection, although the link is controversial [ 5 , 8 , 9 ]. Patients should be instructed to report back to the office if they notice any tenderness, redness, or swelling consistent with infl ammation.
If patients are dissatisfi ed with the treatment modality or progress, they may be referred to one of the above specialists for more aggressive therapy. Patients choosing conservative treatment should be made aware of the likelihood they may need to return for multiple treatments. In most cases, any nail abnormalities return to normal after the DMC has resolved, or when the nail grows out [ 8 ].
Questions for the Dermatologist
– Is the I&D done on digital mucous cysts different than the I&D done for abscesses
or paronychia? Could the I&D have been done in a primary care office?
Digital mucous cysts are incised and drained in the same way, and this procedure can
be performed in primary care. However, they have a higher recurrence rate when they
are treated in this manner, which is one of reasons to excise them rather than I&D.
– Will the nail bed become normal again after the cyst has been drained and
removed?
The nail itself will grow out normally as long as the nail matrix was not traumatized.
There may be dystrophy if the DMC caused trauma to the nail matrix.
– Can digital mucous cysts become infected? Do they ever require antibiotics?
DMCs do not tend to become infected. Antibiotics would only be warranted if a
secondary infection occurred after manipulation of the DMC.
– If the cyst starts draining on its own, does it require further I&D , or is it considered
to be resolving?
If the cyst starts draining on its own, it may not require further treatment. Monitoring
the area of recurrence would be an acceptable approach.
References
1. Park SE, Park EJ, Kim SS, KIM CW. Treatment of digital mucous cysts with intralesional sodium tetradecyl sulfate injection. Dermatol Surg. 2014;40(11):1249–54.
2. Salerni G, Alonso C. Images in clinical medicine. Digital mucous cyst. N Engl J Med. 2012;366(14):1335.
3. Hur J, Kim YS, Yeo KY, Kim JS, Yu HJ. A case of herpetiform appearance of digital mucous cysts. Ann Dermatol. 2010;22(2):194–5.
4. Hernández-Lugo AM, Domínguez-Cherit J, Vega-Memije ME. Digital mucous cyst: the ganglion type. Int J Dermatol. 1999;38(7):533–5.
5. de Berker D, Lawrence C. Ganglion of the distal interphalangeal joint (myxoid cyst): therapy by identifi cation and repair of the leak of joint fl uid. Arch Dermatol. 2001;137(5):607–10.
6. Zuber TJ. Offi ce management of digital mucous cysts. Am Fam Physician. 2001;64(12): 1987–90.
7. Loder RT, Robinson JH, Jackson WT, Allen DJ. A surface ultrastructure study of ganglia and digital mucous cysts. J Hand Surg Am. 1988;13(5):758–62.
8. Johnson SM, Treon K, Thomas S, Cox QG. A reliable surgical treatment for digital mucous cysts. J Hand Surg Eur Vol. 2014;39(8):856–60.
9. Arenas-Prat J. Digital mucous cyst excision using a proximally based skin fl ap. J Plast Surg Hand Surg. 2014;11:1–2.