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SEER Inquiry System - Report
Produced: 05/29/2026 3:45 PM
Question 20250020
Inquiry Details
References:
#1: College of American Pathologists (CAP). CAP Protocol, Vulva
#2: Solid Tumor Rules. Other Sites, 2025 Update
Question:
Solid Tumor Rules/Histology--Vulva: Can instructions and descriptions from registry manuals be used to determine p16 status for the human papillomavirus (HPV)-related histology codes in the Solid Tumor Rules (STR)? Does it have to state that p16 is “positive” or “over-expressed” only? See Discussion.
Discussion:
The STR states that p16 can be used to code HPV-associated and HPV-independent histologies for selected sites depending on diagnosis year but contains no instructions about how to interpret p16 staining results on pathology reports. These are often stated in various ways in our area, depending on the pathology lab and different pathologists. The SSDI Manual and SEER Coding and Staging Manual each have some instructions and code definitions for p16, including:
- Code 0 for p16 expression of weak intensity or limited distribution
- Code 0: p16 Negative; Nonreactive
- Code 1: p16 Positive; Diffuse, Strong reactivity
- IHC for p16 expression is a surrogate marker for HPV infection
Example: 2023 squamous cell carcinoma of the vulva, partial vulvectomy; pathology states vulvar intraepithelial neoplasia-3, p16 immunohistochemistry demonstrates block-like expression, which supports the diagnosis. The next path report states invasive squamous cell carcinoma, stain for p16 is strong and diffuse in the lesion, supporting the above diagnosis. Neither path report specifically states "HPV-related," so are p16 "expression" and "strong and diffuse" staining enough to code the histology as 8085/3 for this case?
Answer:
Refer to the College of American Pathologists (CAP) protocols to determine how to interpret p16 staining results on pathology reports. Per the Vulva CAP Protocol, p16 positive is defined as diffuse or block-like expression. Since the pathology report states "block-like expression," code the histology as 8085/3 (invasive squamous cell carcinoma, HPV-associated).
