Predictive indicators for thyroid cartilage involvement in carcinoma of the larynx seen on spiral computed tomography scans

Objectives: Recent studies have shown that the spiral computed tomography (CT) scan is a sensitive imaging modality for predicting neoplastic invasion of thyroid cartilage. The objectives of our study were: to assess the accuracy of pre-operative spiral CT in predicting thyroid cartilage involvement in patients with carcinoma of the larynx; and to elucidate the factors that would accurately indicate cartilage involvement.Material and methods: Medical records, including spiral CT scans and pathological reports, were reviewed for 27 patients who had undergone laryngectomy in two major hospitals in south Wales. A consultant radiologist with special interest in cross-sectional imaging re-evaluated the scans to assess neoplastic involvement of the thyroid cartilage, based on definite, objective criteria. These criteria included: soft tissue asymmetry; loss of medullary space; spiky or irregular surface; distortion of cartilage framework; and abnormal soft tissue on both sides of the cartilage. The radiological findings were then correlated with the histopathological evidence of cartilage invasion by the tumour.Results: Out of the 27 cases, 15 had evidence of histological invasion of thyroid cartilage. The most specific criterion to predict thyroid cartilage involvement was the presence of tumour on both sides of the cartilage (specificity of 91 per cent, sensitivity of 66 per cent). Combining two criteria increased both the sensitivity and the specificity to 86 and 91 per cent, respectively.