CK7 expression in carcinomas of the Waldeyer's ring area

Primary carcinomas of the Waldeyer's ring area are typically nonkeratinizing squamous cell carcinomas (SCC). Their cervical lymph node metastases are not uncommonly cystic and filled with necrotic tumor cells. Some cysts, however, contain clear fluid. During the investigation of SCC producing "fluid-filled" cystic metastases, we evaluated hematoxylin and eosin (H&E) sections of 90 primary SCC for their site of origin. We analyzed the cytokeratin (CK) profile of primary and metastatic carcinoma with special focus on the expression of CK7, a putative marker for ductal differentiation. CK7 was expressed in submucosal minor salivary gland acini and ducts, but not in the squamous surface epithelium of the Waldeyer's ring. CK7 was expressed in 11 primary SCC (8 base of tongue/3 palatine tonsil). The CK7-positive SCC were deep-seated, arose from large excretory ducts of submucosal minor salivary glands, and showed only insignificant surface involvement. They were characterized by a solid infiltrative growth pattern of basaloid cells with focal ductal differentiation. Salivary ducts adjacent to the carcinoma showed extensive intraductal hyperplasia and metaplasia. All CK7-positive carcinomas produced CK7-positive cystic nodal metastases, most of which contained paucicellular fluid. No solid CK7-positive nodal metastases were identified. In summary, a subset of carcinomas occurring in the Waldeyer's ring area appear to arise from large excretory ducts of submucosal minor salivary glands with only limited surface involvement, express CK7, and produce CK7-positive cystic "fluid-filled" nodal metastases. The histomorphology and immunophenotype suggest that these carcinomas represent basaloid SCC arising from excretory ducts of the submucosal minor salivary glands.