Middle Ear Aspiration Cytology via Otoendoscope-Guided Myringotomy Reliably Confirms Tympanokeratoma in Dogs

The purpose of this study was to determine the correlation between cytology and histology in the diagnosis of canine tympanokeratoma. Dogs that had a middle ear aspiration cytology via otoendoscope-guided myringotomy and a histology of the tympanic bulla content sampled following total ear canal ablation with lateral bulla osteotomy between 2010 and 2024 in one hospital were retrospectively examined. Cytological diagnosis of tympanokeratoma was considered when the sample contained a majority of corneocytes. Thirty-seven ears with a pathological diagnosis of either tympanokeratoma (31/37) or nontympanokeratoma otitis media (6/37) were chosen. Cytology had an accuracy of 78%, a sensitivity of 74%, and a specificity of 100% for diagnosing tympanokeratoma, with negative and positive predictive values of 43 and 100%, respectively. Among ears with histologically confirmed tympanokeratoma, imaging showed lysis and expansion of the tympanic bulla in 45.2 and 12.9%, respectively. Otoendoscopy showed a mass in the horizontal ear canal in 22.6%. Dense opaque pearly yellowish material was sampled from the tympanic cavity in 45.2%. Middle ear aspiration cytology via otoendoscope-guided myringotomy is a useful tool for diagnosing tympanokeratoma and is highly reliable in cases of positive outcomes. However, its capacity to rule out the condition is limited, particularly in infected ears.