Digital myxoid pseudocyst pathology

Digital myxoid pseudocyst is also known as a digital mucous cyst. It is a focal collection of mucin under the skin, and is commonly seen on the distal aspect of the fingers. It is usually a solitary lesion that is skin coloured to translucent.

The corresponding nail can show a grove or structural changes as a pressure effect of the pseudocyst. Osteoarthritis can accompany it, when it is regarded as a type of ganglion. There can be multiple pseudocysts in patients with chronic arthritis. Treatment is mainly to evacuate the content or to remove the cyst using destructive methods or surgery.

Histology of digital myxoid pseudocyst

Digital myxoid pseudocysts can be of two varieties: myxomatous and ganglion.

• The myxomatous type has a focal deposition of mucin in the dermis with surrounding fibrous stroma and no epithelial lining (figures 1–3).
• A ganglion is lined by a fibrous wall or a synovial sac.

Mucin appears slightly bluish in routine hematoxylin and eosin stained slides.

Figure 1

Figure 2

Figure 3

Special studies for digital myxoid pseudocyst

Colloidal iron, Alcian blue, and toluidine blue stains are used to highlight the mucin.

Differential diagnosis of digital myxoid pseudocyst

Focal cutaneous mucinosis.