Hidradenoma masquerading digital ganglion cyst: A rare phenomenon.
BACKGROUND
Mucous cyst is the commonest soft tissue tumor in the dorsum of the distal interphalangeal joint (DIPJ) of the finger. We report the first case of a recurring eccrine tumor (nodular hidradenoma), mimicking a mucous/ganglion cyst, on the dorsum of the DIPJ.


METHODS
A 54 year old man presented with painless, hemispherical, colored swelling on the dorsum of his right middle finger (dominant hand), which appeared to have recurred from a previous surgery. The lesion was excised and operative findings from the medical notes showed the gross appearance to be a soft, white, glistening, smooth-surfaced, myxoid nodule resembling a "ganglion cyst". Immunohistochemistry showed the tumour to be positive for S100, smooth muscle actin and cytokeratin 7. Ductal differentiation was confirmed by staining for epithelial membrane antigen and carcinoembryonic antigen. The histological features were that of atypical and solid cystic hidradenoma.


CONCLUSIONS
This is the first reported case of this rare tumour presenting as mucous cyst. We conduct a review of the literature of nodular hidradenomas, illustrating the immunohistologic findings in this tumour to emphasise the atypical features.We emphasise the importance of considering hidradenoma in the differential diagnosis of such lesions of the finger, in view of its high recurrence rate and the possibility of malignant transformation.
Department of Surgery, Ninewells Hospital & Medical School, University of Dundee, Dundee, DD1 9SY, UK.
Navnit
N
Makaram
St. James's University Hospital, 16 17 Beckett St., Leeds, West Yorkshire, LS9 7TF, UK.
Iskander H
IH
Chaudhry
Royal Blackburn Hospital, East Lancashire Hospitals NHS Trust, Blackburn, BB2 3HH, UK.
Makaram S
MS
Srinivasan
Adnexal tumour; Eccrine; Ganglion cyst; Hand; Hidradenoma