Initial diagnosis of small lymphocytic lymphoma in parotidectomy for Warthin tumour, a rare collision tumour.

Warthin tumours (WT) and malignant lymphomas are only rarely associated, and most are examples of involvement of the lymphoid stroma of WT by a disseminated lymphoma. This report describes a case where excision of a parotid mass led to the initial diagnosis of WT and small lymphocytic lymphoma (SLL). The diagnosis of SLL was confirmed by immunohistochemistry and molecular studies. The patient had stage IV A disease and is currently in chemotherapy induced complete remission. This case highlights the extremely rare association of SLL with WT and the importance of evaluation of the WT stroma, where the pale proliferation centres of SLL may mimic germinal centres of reactive lymphoid nodules.