August Case of the Month

Clinical History: A 28-year-old man with progressively worsening dyspnea on exertion was noted on chest imaging to have a near-completely-obstructing endoluminal lesion in the distal trachea. He is a never smoker and endorsed no significant past medical history. Bronchoscopy confirmed the presence of a lobulated, partially-obstructing endotracheal lesion (Figure 1). A rigid bronchoscope was used to core out the lesion and electrocautery was applied to the base for tissue ablation and hemostasis. Histologic sections (Figures 2-5; H&E) demonstrated a circumscribed epithelial neoplasm composed of expansile nests of clear cells with only mild cytologic atypia. The clear cells were admixed peripherally with slightly larger-appearing cells characterized by eosinophilic cytoplasm and occasional small central nucleoli. Scattered throughout the tumor were collections of mucin-containing cells with occasional small cysts. A somewhat arborizing vascular network with some hyaline-appearing fibrosis was also present. Mitoses were not apparent and neither keratinization nor necrosis were identified. The over lying tracheal epithelium demonstrated early evidence of squamous metaplasia, but no overt cytologic atypia. Immunohistochemical stains (Figure 6) demonstrated the lesional cells to be diffusely CK7 positive with focal collections of cells demonstrating p40 and CK5/6 positivity. The lesional cells were TTF-1 negative.

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