## Pathological Hallmark of Cholesteatoma **Key Point:** The **pathognomonic feature** of cholesteatoma is the presence of **stratified squamous epithelium (keratinizing) lining the middle ear and mastoid, with underlying bone erosion**. ### Histopathology Cholesteatoma is defined by three essential components: 1. **Stratified squamous epithelium** (keratinizing) 2. **Lamina propria** (fibrous tissue with chronic inflammation) 3. **Bone erosion** (osteoclastic activity) ### Distinguishing Features from Chronic Otitis Media | Feature | Cholesteatoma | CSOM without Cholesteatoma | |---------|---------------|---------------------------| | Epithelial lining | Stratified squamous (keratinizing) | Respiratory epithelium or granulation | | Bone erosion | Yes (characteristic) | Minimal or absent | | Keratin accumulation | Yes (pathognomonic) | No | | Osteoclastic activity | Prominent | Absent or minimal | | Ossicular involvement | Erosion common | Erosion less common | **High-Yield:** The **bone-eroding property** of cholesteatoma is what makes it dangerous—it can erode the ossicles, facial canal, lateral semicircular canal, and tegmental bone, leading to serious complications. **Mnemonic: SKEBC** — **S**tratified squamous epithelium, **K**eratin accumulation, **E**rosion of bone, **B**ackground of chronic inflammation, **C**haracteristic of cholesteatoma. ### Clinical Correlate The osteoclastic bone erosion is mediated by inflammatory cytokines (TNF-α, IL-6, IL-8) and explains why cholesteatoma, even if small, can cause severe complications like facial nerve paralysis or sensorineural hearing loss. 
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