External Auditory Canal Eccrine Hidrocystoma and Equivocal Actinic Keratosis: A Rare Combination and Review of the Literature.

Eccrine hidrocystoma is a rare benign cyst arising from the sweat glands, whereas actinic keratosis is a premalignant cutaneous lesion. Scheuermann's kyphosis is a structural spinal disorder typically identified during adolescence. The coexistence of these conditions has not previously been reported. A patient in their early 70s presented with a blue, dome-shaped cyst located in the deeper portion of the external auditory canal. Surgical excision was performed, and histopathological examination revealed an eccrine hidrocystoma with equivocal features of actinic keratosis. The patient also had a known diagnosis of Scheuermann's kyphosis. Although the hidrocystoma was completely excised, the premalignant potential of actinic keratosis necessitated close clinical follow-up. This rare case underscores the importance of comprehensive histopathological evaluation and vigilant monitoring of potential premalignant lesions. Awareness of such uncommon associations may aid clinicians in optimizing management strategies and ensuring appropriate long-term follow-up.