Benign epithelial inclusion consisting of squamous metaplasia and small glandular elements in regional lymph node of a patient with tongue cancer: a case report and literature review

There are occasional reports of unexpected pathological findings during neck dissection, including benign inclusions (BIs) in cervical lymph nodes, comprising squamous epithelial, glandular, thyroid, neval and mesothelial cells. BIs can mimic regional lymph node metastases, therefore, pathological diagnosis is important. However, criteria for immunohistochemical diagnosis of BIs are not established. We report a 73-year-old woman with tongue cancer with squamous metaplasia and a glandular BI in a regional lymph node. Clinical and radiographic assessment of the lesion led to diagnosis of tongue squamous cell carcinoma (T3N2bM0, Stage IVa). The patient underwent right-side total neck dissection with wide local excision of the tongue tumor. All the lymph nodes in the dissection specimen were pathologically negative. In contrast, one BI in a level III lymph node was found incidentally. We could not diagnose this lesion clearly by routine pathological examination because of the lack of criteria for immunohistochemical diagnosis of BIs. To the best of our knowledge, BIs comprising squamous metaplasia and small glandular elements in the regional lymph nodes of patients with head and neck cancer have not been reported. We histologically predicted the lesion as BI, which was confirmed by additional immunohistochemical staining for cytokeratin 13 and 17. Clinicians should avoid misdiagnosis of metastases, which could lead to incorrect tumor staging and inadequate adjuvant therapy for patients with lymph node BIs. To distinguish BIs from metastases clearly, we recommend additional immunohistochemical staining for cytokeratin 13 and 17 in routinely stained sections of regional lymph nodes in patients with squamous cell carcinoma.