Assessment of Acquired "Sheet-Like" Cholesteatomas on Temporal Bone Computed Tomography.

BACKGROUND: Primary acquired cholesteatomas (PAC) are typically mass-like rounded opacities beginning in the lateral epitympanum that result in osseous erosion. Uncommon presentations of acquired cholesteatoma have been described in the Otolaryngology literature, including en-plaque or sheet-like appearance. PURPOSE: To describe findings of histologically confirmed sheet-like cholesteatoma (SLC) and evaluate the diagnostic performance of two experienced head and neck radiologists for the detection of SLC on temporal bone CT (TBCT). MATERIALS AND METHODS: Retrospective review of 13 SLC patients, 16 PAC patients, and 8 patients with no cholesteatoma was performed. All patients underwent TBCT and had surgical and pathologic confirmation of disease presence/absence. Two radiologists (45 and 29 years-experience), blinded to diagnosis and study design, independently evaluated the TBCTs for cholesteatoma using a 5-point Likert scale (1-5; higher scores indicating greater confidence in the presence of cholesteatoma). Diagnostic performance was evaluated with receiver operating characteristic (ROC) analysis, with area under the curve (AUC) calculated for each reader. Sensitivity and specificity were calculated. Inter-reader agreement was measured by Cohen's kappa (κ). RESULTS: SLC did not appear as a discrete, solid mass on CT. 61% (8/13) appeared as plaque-like thickening of the tympanic membrane (all with history of perforation/instrumentation), without obvious osseous erosion. 38% (5/13) showed curvilinear, shell-like lamellated tissue in the middle ear (3/5) or mastoid (2/5). For SLC detection, sensitivity and specificity were 43% and 100% (reader 1), and 53% and 71% (reader 2), respectively. For PAC, sensitivity, specificity were 94% and 100% (reader 1) and 94% and 100% (reader 2), respectively. Mean Likert scores for SLC were 3 (reader 1) and 2.3 (reader 2), with moderate agreement (ć=0.49; 95% CI:0.13-0.86); for PAC, scores were 4.7 and 4.4, with excellent agreement (ć=0.80; 95% CI:0.54-1.00). CONCLUSIONS: SLC is an uncommon subtype of cholesteatoma with potentially subtle imaging features, without the typical nodular appearance of a PAC, posing a diagnostic challenge. Radiologists should be aware of this variant and report findings cautiously to support accurate clinical management.