Differential Diagnosis for Branchial Cleft Cyst FNAC in a Young Patient
- Single most likely diagnosis + Lymphocytes: Branchial cleft cysts are congenital anomalies that often present in young patients. They can be filled with lymphoid tissue, and fine-needle aspiration cytology (FNAC) may yield a predominance of lymphocytes, reflecting the cyst's content or associated lymphoid tissue.
- Other Likely diagnoses + Squamous cells (possibly with a mention of P16 status but not explicitly negative): Branchial cleft cysts can also contain squamous cells, as the cyst lining may be squamous epithelium. The mention of P16 is often related to the context of identifying squamous cell carcinoma, particularly in the context of HPV-related cancers, but in the case of a branchial cleft cyst, the presence of squamous cells does not necessarily imply malignancy.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.) + Squamous carcinoma: Although less common, it is crucial to consider the possibility of squamous cell carcinoma, especially if the clinical presentation is atypical or if there are concerning features on imaging. Metastatic squamous cell carcinoma to lymph nodes in the neck can mimic a branchial cleft cyst, and a thorough evaluation, including the search for a primary tumor, is essential.
- Rare diagnoses + Other rare entities that could present similarly include metastatic disease to lymph nodes, unusual infections (e.g., tuberculosis), or other congenital anomalies. However, these are less likely given the specific context of an MRI suggesting a branchial cleft cyst and the age of the patient.
It's essential to approach each case with a thorough consideration of the clinical context, imaging findings, and laboratory results to ensure that the diagnosis is accurate and that no critical conditions are overlooked.