Clinicopathologic features and outcome of head and neck mucosal spindle cell squamous cell carcinoma.

Spindle cell squamous cell carcinoma (SpC-SCC) is rare, accounting for 0.4-4% of head and neck (HN) SCCs. Better understanding of HN SpC-SCC clinicopathologic characteristics, especially features that predict outcome, is needed. We present a clinicopathologic review of 71 HN mucosal SpC-SCC from three tertiary centers. The patient population showed a median age of 63 years (range 20-91), slight male predominance (M:F = 1.6:1), and a preponderance of smokers/ex-smokers (45/71, 64%). Most lesions involved oral cavity (42/71, 59%), especially oral tongue (n = 18), and larynx (n = 20, 28%). Polypoid/exophytic growth and surface ulceration were seen in 60% and 86% of cases, respectively. Histologically, most tumors showed sarcoma-like pattern (65/70, 93%), the remaining exhibiting granulation tissue-like or fibromatosis-like patterns, and 5 lesions showed osteosarcomatous/chondrosarcomatous elements. Most tumors (53/71, 74%) showed a conventional SCC (C-SCC) component, keratinizing (86%) or non-keratinizing/basaloid (14%). Nodal metastases, seen in 22 (31%) of resection specimens, showed SpC-SCC and/or C-SCC histomorphology. By immunohistochemistry, 76% of lesions showed immunoreactivity for keratin and 62/60% of lesions were p40/p63 positive. Ki-67 proliferation index ranged from 5 to 70%. Follow-up was available on 69 patients, median of 1.1 years from the time of SpC-SCC diagnosis. The 3-, 5-, and 10-year disease-specific survival (DSS) was 62, 37, and 12%, respectively. AJCC pN stage was an independent prognostic factor for DSS and distant metastasis-free survival (DMFS), whereas the presence of C-SCC was independently associated with improved DMFS. HN SpC-SCC is rare and might be diagnostically challenging. AJCC pN stage and co-existing C-SCC component appear to be prognostically relevant.