Pitfalls in the cytodiagnosis of metastatic squamous cell carcinoma in the head and neck: A retrospective study

Background: Lateral neck swelling in an adult is a common presentation for primary and secondary malignant lesions. Metastasis from squamous cell carcinoma often leads to various secondary changes in the lymph nodes, which makes their diagnosis on cytology a difficult task. Sometimes, the primary sites remain occult and any false negative cytological diagnosis becomes a misleading factor. Aim: Our aim was to evaluate the efficacy of fine needle aspiration cytology (FNAC) in diagnosing metastasic squamous cell carcinoma in the head and neck, and to highlight the precautions that can reduce the rate of false negative diagnosis. Materials and Methods: Two thousand five hundred and twelve patients in an age range of 18 to 80 years and presenting with a solitary lateral swelling of the neck were selected for this study. Results: Three hundred and seventy positive and 45 suspicious cases of metastatic squamous cell carcinoma were detected by FNAC; there were 15 false negative cases. All of them were associated with cystic change, abscess, or necrosis. The primary sites for carcinoma were the tonsil, tongue, pharynx, and larynx. No primary site could be detected in three cases. Histopathological confirmation was done in all the cases. The specificity and sensitivity of FNAC in the detection of positive cases of metastatic squamous cell carcinoma were 96.05 and 96.5% respectively. Conclusions: Any lateral neck swelling in adult patients that is associated with cystic change, abscess, or necrosis on FNAC should be carefully searched for malignant cells. Clinical re-evaluation and image guided surgical biopsy should supplement FNAC in suspicious cases. In spite of the possible limitation of a false negative diagnosis, FNAC remains a useful tool in diagnosing metastasis with good certainty