Basaloid squamous cell carcinoma of floor of mouth

Background. Only five cases of basaloid squamous cell carcinoma (BSCC), a rare tumor of head and neck, have been reported to involve the floor of mouth. Methods. Clinicopathologic and immunohistochemical features of eight BSCC of floor of mouth were studied to evaluate the significance of the basaloid features. Results. Five patients were male and three were female. Their mean age was 52 years (range, 39–59). At presentation, one patient was diagnosed with Stage II disease, four were diagnosed with Stage III disease, and three were diagnosed with Stage IV disease. Aside from typical squamous differentiation, each patient had a component of basaloid cells arranged in irregular nests, cords, or pseudoglandular spaces with a brisk mitotic rate, myxoid stroma, and marked tendency for perineural invasion. A panel of immunostains yielded 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 characterization 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, five 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 patients had recurrent disease. The authors compared these data with a control 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.