Prevalence of Micrometastasis and Isolated Tumour cells in lymph nodes of Head and Neck Squamous cell carcinoma

Lymph node metastasis significantly impacts prognosis in head and neck squamous cell carcinoma (HNSCC). Micrometastasis (MM) and isolated tumour cells (ITC) may escape detection on routine histopathology, leading to potential understaging. To evaluate the prevalence of MM and ITC in clinically node-negative HNSCC and compare detection rates between conventional histopathology and immunohistochemistry (IHC). This prospective and retrospective observational study included 22 patients with clinically node-negative HNSCC who underwent neck dissection between January 2019 and April 2024. A total of 510 lymph nodes were examined. Previously reported negative lymph nodes were re-evaluated using hematoxylin and eosin (H&E) staining, followed by deeper sectioning at 150 µm intervals. IHC using pan-cytokeratin (Pan-CK) was performed on one representative lymph node block from each neck level. MM (>0.2 mm to ≤2 mm) and ITC (≤0.2 mm) were assessed. The mean age was 57.68 ± 12.07 years, with male predominance (59.1%). Most tumors arose from the oral cavity (95.45%), particularly the lateral tongue. Pathological staging showed 86.4% N0 and 13.6% N1 disease. Neither re-evaluation of H&E sections nor deeper sectioning identified MM or ITC. IHC also demonstrated no positivity, resulting in a 0% detection rate across all modalities. MM and ITC were not detected in this cohort. IHC did not provide additional diagnostic yield over conventional histopathology, suggesting limited utility in routine evaluation of node-negative HNSCC.