What additional work up would you do for a T1bN2 squamous cell carcinoma of the true larynx if endoscopy demonstrates a true cord lesion extending to the commissure with normal mobility and no evidence of supra or subglottic extension?

I assume that PET-CT was performed and demonstrated only the neck and the laryngeal lesion. The histology of VC cancer is usually well-differentiated. I would examine a needle biopsy of the nodes for discrepancy in histology and stain for p16 for the possibility of a second, unknown primary, which these days is often HPV related and assumed to be of OPC origin. If the endoscopy was focused on the VC, I would repeat a pan-endoscopy with biopsies of potential sites of an unknown second primary, esp. the oropharynx if the nodal biopsy was p16+.

Aside from the rarity of this presentation, I think the workup would be similar to any advanced laryngeal cancer, with the appropriate staging, including imaging that reflects the anatomic and metabolic extent of disease, and the appropriate consults to the ancillary services that inform the final treatment plan (i.e., dental, nutrition, speech path, audiology, as CIS is likely to be considered). I can't envision many differences other than nuances of target delineation to the primary compared to a slightly more common T1N2 supraglottic cancer.