Final answer:
The primary determinant of nodal metastases in squamous cell carcinoma of the vulva is the depth of invasion, with deeper invasion increasing the risk of spread to lymph nodes.
Step-by-step explanation:
The primary determinant of nodal metastases (mets) in squamous cell carcinoma of the vulva is b) Depth of invasion. The prognosis and staging of vulvar cancers, including the risk of nodal metastases, are highly associated with the depth to which the tumor has invaded the surrounding tissue. The deeper the invasion, the more likely are the chances of spreading to the lymph nodes. Other factors, like tumor size or presence of ulceration, also contribute to the risk of metastasis but to a lesser extent compared to the depth of invasion. Age of the patient is less significant in determining nodal metastasis in this context. Squamous cell carcinomas, as presented in the student's question, are the second most common type of skin cancer, affecting the squamous cells which make up most of the skin's upper layers (the epidermis). If not treated, these cancers have the potential to spread to other parts of the body (invasive tumors).