Case Report: A rare case of over 45 years' survival in a patient with tonsillar adenoid cystic carcinoma.

Tonsillar adenoid cystic carcinoma (TACC) is an extremely rare malignancy with an unpredictable clinical course. We report an unusual case of TACC with a 47-year disease trajectory, characterized by prolonged indolent behavior followed by late and relatively rapid clinical progression. The patient was initially diagnosed with left tonsillar ACC in 1977 after presenting with dysphagia and underwent tonsillectomy followed by postoperative radiotherapy. A local recurrence involving the left soft palate occurred in 1996-1997 and was treated with surgical resection and tongue flap reconstruction, after which the disease remained clinically stable for many years. In 2018, recurrent ACC of the soft palate was confirmed in the radical resection specimen, and the patient underwent radical resection via a mandibulotomy approach followed by reconstruction and adjuvant concurrent chemoradiotherapy. Molecular profiling of the available 2018 recurrent soft palate lesion revealed NOTCH2 copy number gain and structural variants involving MTOR and SPEN. Regional cervical lymph node metastasis was confirmed in 2022, followed by intracranial disease progression in 2023. The patient died in 2024 from complications of progressive intracranial and systemic metastases. To our knowledge, this represents one of the longest documented clinical courses of TACC with integrated genomic analysis. This case highlights the potential for TACC to remain indolent for decades before transitioning to late regional and systemic progression, underscoring the importance of long-term surveillance and comprehensive clinicopathological and molecular evaluation.