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SEER Inquiry System - Report
Produced: 10/15/2026 10:47 AM
Question 20260016
Inquiry Details
References:
#1: Solid Tumor Rules. Head and Neck, 2026 Update, Dec. 12, 2025
#2: WHO Class H & N Tumors. 5th edition, online version
Question:
Solid Tumor Rules/Histology--Head & Neck: How is the histology of a sinonasal tumor coded when the initial biopsy addendum diagnosis is "High-grade malignant neoplasm with features in between olfactory neuroblastoma and large cell neuroendocrine carcinoma" and the repeat biopsy diagnosis is "High-grade neuroendocrine carcinoma?" See Discussion.
Discussion:
The patient has an overlapping sinonasal tumor and only underwent diagnostic biopsies of the ethmoid sinus component. Neither biopsy can be determined to be the more representative specimen. The initial biopsy, addendum diagnosis, states there are features in between olfactory neuroblastoma and large cell neuroendocrine carcinoma. The addendum comment states the findings, "makes the distinction between olfactory neuroblastoma (ONB) and neuroendocrine carcinoma difficult."
The final diagnosis on the repeat biopsy (approx. 2 weeks later) was high grade neuroendocrine carcinoma, but the diagnosis comment states, "There are no features to suggest underlying olfactory neuroblastoma; however, the material may not be representative of the entire tumor." The managing physician states this is most consistent with olfactory neuroblastoma (esthesioneuroblastoma) in the medical record.
If this were a mixed histology tumor, there is no applicable H Rule in the Head & Neck schema. It is unclear which biopsy diagnosis to use since there is conflicting information. Should this be coded as an olfactory neuroblastoma per the initial biopsy diagnosis and the diagnosis provided by the physician? Or should this be a high grade neuroendocrine carcinoma as it is likely the tumor component with the worst prognosis?
Answer:
Assign 9522/3 (olfactory neuroblastoma) as a single histology to this case based on the initial pathology and managing physician’s diagnosis. World Health Organization Classification Head and Neck Tumors, 5th edition defines olfactory neuroblastoma as a malignant neuroectodermal neoplasm derived from the specialized sensory olfactory neuroepithelium.
