Tonsillar Lymphangiomatous Polyp Mimicking a Vallecular Cyst in an Adult: A Case Report

Tonsillar lymphangiomatous polyps are rare benign lesions characterized histologically by dilated lymphatic channels within a fibrous, adipose, or lymphoid stromal background. Although these lesions are more commonly reported in children and young adults, they are uncommon in older adults and may mimic other oropharyngeal or laryngeal lesions, including vallecular cysts.

We report the case of a 42-year-old previously healthy male who was incidentally found to have a mass at the base of the tongue. Preoperative clinical and radiologic assessment suggested a laryngeal vallecular cyst, as computed tomography demonstrated a well-defined lesion occupying the left epiglottic vallecula with partial airway narrowing. However, intraoperative examination revealed that the lesion was pedunculated and originated from the left tonsil rather than the vallecula. The patient underwent surgical excision with left tonsillectomy. Histopathologic examination demonstrated a lesion covered by squamous epithelium and composed of multiple dilated lymphatic vascular channels within a fibrous stromal background. Immunohistochemical staining showed endothelial positivity for D2-40, supporting lymphatic differentiation and confirming the diagnosis of a tonsillar lymphangiomatous polyp.

This case highlights the diagnostic challenge of tonsillar lymphangiomatous polyps, particularly when a pedunculated tonsillar lesion projects toward the vallecula and clinically or radiologically mimics a vallecular cyst. Careful intraoperative assessment of the lesion's attachment site is essential for accurate localization and diagnosis. Complete surgical excision remains both diagnostic and therapeutic.