An official website of the United States government
Home
SEER Inquiry System - Report
Produced: 07/18/2025 10:42 PM
Question 20230009
Inquiry Details
References:
#1: Solid Tumor Rules. Other Sites, 2023 Update
#2: WHO Class Female Genital Tumors, online version. Female Genital Tumors, 5th ed.
Question:
Solid Tumor Rules/Multiple Primaries--Vulva: How many primaries are accessioned when a 2023 diagnosis of keratinizing squamous cell carcinoma (SCC) (8071/3) of the vulva follows a previous diagnosis of nonkeratinizing SCC (8072/3) of the vulva and the timing rule (M12) does not apply? See Discussion.
Discussion:
Table 19: Vulva Histologies of the Other Sites Solid Tumor Rules does not include entries for either keratinizing or nonkeratinizing squamous cell carcinoma in the “Squamous cell carcinoma, NOS” row. However, these are two distinctly different histologies per the ICD-O-3.2.
All other Solid Tumor Rules schemas include an M Rule instructing one to abstract multiple primaries when separate/non-contiguous tumors are two or more different subtypes/variants in Column 3 of the Specific Histologies, NOS, and Subtype/Variants Table for the schema (e.g., Rule M6 for Lung). The timing of these tumors is stated to be irrelevant. The Notes confirm the tumors may be subtypes/variants of the same or different NOS histologies and tumors in column 3 are all distinctly different histologies (even if they are in the same row). However, the 2023 Other Sites schema appears to be missing this rule.
Should these distinctly different histologies be accessioned as separate primaries? Is an M Rule missing from the Other Sites schema to address distinctly different histologies?
Answer:
Table 19 is based on WHO 5th Ed Tumors of vulva and squamous cell variants, keratinizing and non-keratinizing, are no longer recommended and are excluded from the 5th Ed. HPV related terminology is now preferred for these neoplasms.
Per consultation with our GYN expert pathologist, based on the information provided, this is likely a single tumor that was not completely excised in the original biopsy. A new tumor in the same site would not appear within 8 months. If you cannot confirm two separate/non-contiguous tumors were present, abstract a single primary per M1. As for histology, the tumor showed both keratinizing and non-keratinizing features and HPV status is unclear. Per our expert, code to SCC 8070/3—keratinization or lack of does not change treatment or prognosis.
Even If there is proof of separate/non-contiguous tumors, our expert still feels this is a single primary coded to SCC 8070/3. Treatment does not differ by keratinization or HPV status. Coding two primaries would be incorrect and inflate incidence rates.
Per our expert, this is an unusual occurrence. The rules cover 85% of cases but there will always be situations that do not fit a rule. This case is an example of that. A new GYN specific Solid Tumor Rules module is under development and a rule to address this situation could be included.
