<prompt> The prognosis for squamous carcinoma of the floor of the mouth is adversely affected by which of the following?Composite resection specimen of a T4 floor of mouth squamous cell carcinomaPoor differentiation of tumorNonverrucous carcinomaPresence on left sideNo tongue involvement  <response>: Poorly differentiated squamous cell carcinoma of the floor of the mouth tends to be more invasive than better-differentiated tumors. Poorer prognosis can be expected when invasion is larger than 9 mm, perineural invasion is noted, and lymph node metastasis is evident. 