Carcinoma in situ and microinvasive squamous carcinoma of the laryngeal glottis.

Twenty-five patients with severe squamous intraepithelial neoplasia, grade 3 (SIN III) of the glottis were identified and followed up; three patients (12%) eventually developed invasive carcinoma and nine patients (36%) were noted to have coexisting microinvasive carcinoma. Two of the patients with microinvasive carcinoma were treated by hemilaryngectomy, three with stripping and radiation therapy, two with stripping alone, and two by radiation therapy. None of the patients developed recurrent disease after one to five years of follow-up. This observation supports the approach of treating "true" microinvasive carcinoma similar to carcinoma in situ. The 16 remaining patients were treated by stripping (ten patients), stripping and radiation therapy (four patients), and radiation therapy alone (two patients). Three patients progressed to invasive squamous carcinoma at 35, 39, and 84 months after the diagnosis of SIN III. Patients in this study displaying SIN III with or without microinvasive carcinoma were successfully treated by surgery or radiation therapy alone or by combined therapy. The finding of 12% progression to invasive carcinoma and coexisting microinvasive carcinoma in 36% confirms the preinvasive nature of SIN III of the laryngeal glottis.