Microinvasive Squamous Carcinoma of the Vulva: Search for a Definition

All cases of stage I squamous cell carcinoma of the vulva from the University of Michigan Tumor Registry from 1935 to 1981 were reviewed. Seventeen of 90 (19%) patients had nodal metastases. All had a depth of invasion of more than 2 mm and all exhibited histologic confluence. The risk of nodal metastases varied with depth of invasion, size of lesion, and histologic grade, although the association with grade was not statistically significant. The size of the lesion influenced the incidence of nodal metastases only in that it was associated with the depth of invasion. Lymphovascular invasion was present in only four patients, but three of them had nodal metastases, including one patient with only 3 mm depth of invasion.