BASALOID-SQUAMOUS CELL-CARCINOMA OF FLOOR OF MOUTH

Background. Only five cases of basaloid squamous cell carcinoma (BSCC) , a rare tumor of bead and neck, have been reported to involve the flo or of mouth. Methods. Clinicopathologic and immunohistochemical featur es of eight BSCC of floor of mouth were studied to evaluate the signif icance of the basaloid features. Results. Five patients were male and three were female. Their mean age was 52 years (range, 39-59). At pres entation, one patient was diagnosed with Stage II disease, four were d iagnosed with Stage III disease, and three were diagnosed with Stage I V disease. Aside from typical squamous differentiation, each patient h ad a component of basaloid cells arranged in irregular nests, cords, o r pseudoglandular spaces with a brisk mitotic rate, myxoid stroma, and marked tendency for perineural invasion. A panel of immunostains yiel ded the following results: keratin, +8/8; carcinoembryonic antigen, +3 /8; and S-100, chromogranin, and neuron-specific enolase were negative . Mucin stains were negative in all cases. Ultrastructural characteriz ation of three BSCC revealed squamous differentiation of the basaloid cells and a peculiar basal membrane-like material in between them. No neurosecretory granules were present. Seven patients underwent surgery ; six of them were also treated with postoperative radiation therapy. In two cases, chemotherapy was added at recurrence. One nonresectable patient received radiation and chemotherapy. At the last follow-up, fi ve patients were dead of disease within 13 months from the diagnosis. One patient died of an unknown cause. Two patients were still alive at the time of this report, 4 and 2 months after treatment. Seven patien ts had recurrent disease. The authors compared these data with a contr ol group of patients with conventional squamous cell carcinoma (SCC). Conclusions. The authors' results indicate that BSCC of floor of mouth is an aggressive variant of SCC and is prognostically worse than the conventional SCC, regardless of the grade of the latter.