REPORT OF A CASE
A 67-year-old woman, who had worked on a farm for several years where she also had to milk manually, presented with black nodules on the dorsal (Fig 1) and lateral/volar parts (Fig 2) of the right thumb. These nodules started to grow about 1.5 years ago. Three more nodules were already removed in other outpatient departments. The occasionally bleeding nodules (Fig 2) were painless, but the patient complained of pain when moving the thumb or when it was pressed. The circumferences of both thumbs were smaller than normal but more so on the left thumb. The mobility of both thumbs was reduced, and crepitation was noted. Orthopedic examination, including a roentgenogram, showed a severe degeneration of carpometacarpal joints on both hands and muscular atrophy. Excisional biopsy specimens of two lesions are shown in Figs 3 through 5.What is your diagnosis?
Dorsal mucoid cysts of the finger.
Barth J, Heinisch G. Multiple Black Nodules on the Thumb. Arch Dermatol. 1993;129(5):635-636. doi:10.1001/archderm.1993.01680260105017