Hyams histopathological grading is applied to olfactory neuroblastoma. Which statement about this grading system is correct?

• A It applies only to recurrent tumours
• B It grades tumours I to III based solely on mitotic count
• C It replaces the Kadish system for determining surgical extent
• D It grades tumours I to IV, with grade IV showing the worst prognosis ✓

Explanation

Hyams grading stratifies olfactory neuroblastoma into four grades based on lobular architecture, neurofibrillary matrix, rosettes, nuclear pleomorphism and mitoses, and higher grades correlate with worse survival. It is a histological prognostic tool and does not replace Kadish staging, which defines anatomical extent and guides treatment planning. It applies to all tumours at diagnosis, not only recurrences.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

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