Tumor-associated lymphoid proliferation (TALP) is a well-recognized lymphocytic reaction that is commonly associated with certain salivary gland
tumors. A salivary
carcinoma with TALP may be confused for true lymph node involvement by that
tumor, constituting a potential pitfall in
tumor staging that may result in unnecessary therapeutic intervention or erroneous prognostication for patients. True lymph nodes harbor populations of extrafollicular reticulum cells (ERCs), which can be highlighted by low molecular weight
cytokeratin immunohistochemistry. We sought to determine whether low molecular weight cytokeratin
Cam5.2 immunostaining may be utilized to differentiate true lymph node involvement by salivary gland
tumors from TALP. The surgical pathology archives of the University of Texas Southwestern Medical Center was searched for cases of
salivary gland neoplasms exhibiting either TALP or true lymph node involvement.
Hematoxylin and
eosin-stained sections were examined. Cases were classified on the basis of a definitive lymph node
capsule and subcapsular sinus, as seen on routine histologic evaluation. Low molecular weight
cytokeratin Cam5.2 immunostaining was performed and evaluated on all cases. Twenty-three salivary gland
carcinomas with TALP and 16
carcinomas involving a lymph node (14
carcinomas metastatic to regional lymph nodes and 2
carcinomas arising from benign lymph node inclusions) were identified. Numerous Cam5.2-positive ERCs were identified within the nodal tissue of all true lymph nodes involved by
carcinoma (16 of 16 cases), while Cam5.2-positive ERCs were completely absent in all cases of salivary gland lesions with TALP (0 of 23 cases) (100% vs. 0%, p < .0001, Fisher's Exact). Utilization of low molecular weight
cytokeratin Cam 5.2 immunostaining for ERCs is a highly useful tool for distinguishing true lymph node involvement by salivary gland
carcinomas from TALP. This strategy may be useful in identifying genuine nodal
metastasis in histologically ambiguous cases, and to avoid erroneously upstaging
tumor with TALP as nodal
metastasis with the resulting prognostic and therapeutic implications. Moreover, low molecular weight
cytokeratin immunostaining may be useful in confirming the rare examples of salivary gland
tumors arising from intranodal salivary gland inclusions.