Clinic & Revision
BONE INVOLVEMENT IN ORAL SQUAMOUS CELL CARCINOMA
Bone is involved by direct contact with the tumour.
Invasion occurs in one of two types
1. Erosive: tumour advances on a broad front with a connective tissue layer and active osteoclasts separating the tumour from the bone.
2. Infiltrative: fingers and islands of tumour advance independently into the cancellous spaces, with little osteoclastic activity and no intervening layer of connective
A combination of modalities are generally used:
Clinical examination- limited when poor mouth opening eg trims us from betel nut chewing
CT- best for assessing cortical bone invasion but poor for medullary bone
MRI- best for medullary bone
Bone scintigraphy- best overall but low specificity as get increased uptake in bone disease or periodontal disease
Rim resection (marginal mandibulectomy)
Extent of bone resorption
Extent of bone removal should be determined by the extent of bone resorption after the loss of teeth
Brown et al 2005 (see table below) used the classification of bone resorption pattern in edentulous jaws given by Cawood and Howell (1988) to decide if rim resection or segmental resection better
Need at least 1cm of rim remaining for integrity
If > 5mm of bone involvement on imaging then likely to get segmental resection (Brown paper below)
Contemporary marginal mandibulectomy usually refers to resections of either the inner table or alveolar ridge of the mandible. In the absence of radiographic evidence of mandibular inva- sion, marginal mandibulectomy has been shown to be a sound oncologic procedure for patients with cancers of floor of the mouth. Marginal mandibulectomy has been used in cases in which the tumour abuts the mandible, is adherent to the periosteum, or where resection of the alveolar process is necessary to obtain a third dimension on the deep surface of the tumour.
Perform marginal mandibulectomy in radiologically negative tumours which are close to the mandibular region or abut onto mandible, in dentate or recently extracted cases
In rounded or knife e edge ridges or flat or depressed ridges, with radiological evidence of mandibular invasion, a segmental resection should be done.
Segmental resections cause severe functional and cosmetic problems due to loss of the continuity of the mandible
Functional improvement can only be realistically achieved by microvascular transfer of vascularised bone grafts.
The prognostic impact of mandibular invasion by OSCC is controversial, with conflicting reports in the literature.
Even in the presence of mandibular invasion, soft tissue factors are the most important determinants of prognosis.
Upstaging tumours on the basis of mandibular invasion is justified. An infiltrative pattern of bone invasion is a marker of aggressive tumour biology.
Author: Johno Breeze
Last Update: 25/04/2015