Pathology of Digital Mucous Cyst

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Answer - Digital mucous (myxoid) cysts

Digital mucous (myxoid) cysts usually present as solitary, cystic, dome-shaped nodules.

There are two types of digital mucous cysts:

1) The lesion may be located on the dorsum of the finger near the proximal nail fold.

2) The second type of lesion is present near the distal interphalangeal joint.

It is formed due to herniation of the joint lining, hence representing a ganglion.

Digital mucous cysts usually occur in middle aged or elderly patients.

Microscopic features:

1) The nodules near the proximal nail fold resemble focal mucinosis.

There are large myxoid areas, stellate fibroblasts and small cystic spaces.

The subepidermal collection of mucin causes thinning of the overlying epidermis.

The mucin is demonstrated by mucin stains like colloidal iron stain and alcian blue at pH 2.5.

2) Ganglionic type shows a cystic space with well circumscribed fibrous wall.

Some myxoid areas are present near the wall.

Thin synovial lining may be present.