On 15 June 1888, the German Emperor, Kaiser Friedrich III, died of laryngeal cancer. Three biopsies of his laryngeal lesion had been taken by the British laryngologist, Morel Mackenzie, in 1887 and diagnosed by Rudolf Virchow as "pachydermia verrucosa laryngis", confirming Mackenzie's assessment that the Kaiser's disease was benign. A fourth specimen coughed up by the patient was considered by Virchow to be nondiagnostic. A further specimen expectorated by the patient 3 months before his death was diagnosed as carcinoma by Wilhelm Waldeyer. The autopsy revealed squamous carcinoma in the larynx with a cervical lymph node metastasis. The discrepancies between the initial diagnoses and the final outcome of the Kaiser's disease gave rise to a never-ending medical controversy. Our investigations on this historical case were limited to the official German documents and publications and their English translations and to subsequent literature sources of the time, after having received confirmation that the histological slides and Virchow's original reports had been lost. Based on current surgical pathology knowledge, we propose that the tumour that challenged the diagnostic skills of the founder of pathology was hybrid verrucous carcinoma (HVC), an extremely rare, metastasizing variant of verrucous carcinoma (VC) composed of pure VC mixed with clusters of conventional squamous cell carcinoma. As we see it now, Virchow was therefore not totally wrong. Our retrospective evaluation suggests that Virchow's detailed description of the Kaiser's cancer preceded the paper that contributed to the full understanding of HVC of the larynx by 110 years.