Direct bone invasion in squamous carcinomas of the head and neck: pathological and clinical implications

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Abstract
Direct bone invasion by tumor, an uncommon event at most sites, was demonstrated in 18 of 150 consecutive major surgical specimens from patients with squamous carcinomas of the head and neck. Intraoral carcinomas invading the jaw(s) comprise the single most common group. The tumor gains access to bone by direct spread or along perineural spaces: infiltration of periosteal lymphatics was rare. The morphological phases of bone invasion are described, the main feature being bone destruction by osteoclasts in front of the advancing tumor; tumor cells do not directly impinge on the bone surface until the late stages of invasion. Osteoblastic activity is less marked. Evidence that osteoclasts are directly stimulated by local tumor is discussed. The clinical implications relate to the possible uses of scintigraphy and the need to ensure adequate bone resections in operable lesions: the tumors sometimes infiltrate laterally beneath apparently intact bone cortex (submucosal spread), and the normal tissue planes at the bone-soft tissue interface are usually distorted by previous radiotherapy.