Digital papillary adenocarcinoma: a tumour that should be considered in the differential diagnosis of neoplasms involving the digits.

Background: Digital papillary adenocarcinoma (DPA) is a rare malignant adnexal tumour that occurs almost exclusively in a digital location. Only two case series have been reported previously.

Aims: To document the clinical and histopathological findings in a series of patients with DPA.

Results: Of the 8 patients identified, six were males and two were females, and they were aged between 32 and 76 years at diagnosis. The diagnosis was not clinically suspected in any of the patients, and the tumours were thought to be cysts in four cases. The tumours ranged from 7 mm to 40 mm in size, and were located on the right thumb (n=3), the right middle finger (n = 3) and the left index finger (n = 2). Each tumour exhibited a multinodular growth pattern, with a combination of solid and cystic architecture. Papillary projections were present in many of the cystic spaces. In three cases, some cystic spaces were lined by luminal columnar epithelial cells and underlying myoepithelial cells. Cytological atypia was generally mild and mitotic activity was low in most cases (median 2 mitoses per mm). Local tumour recurrence occurred in three patients, of whom one subsequently had a digital amputation. No metastases have been identified in the seven patients with known follow-up information.

Conclusions: DPA is a rare tumour that should be included in the differential diagnosis of epithelial neoplasms in digital locations. Because of its tendency to recur locally, wide local excision should be performed as definitive initial treatment.