#1: Solid Tumor Rules (2018)
#2: Multiple primaries
#3: Head & Neck
Source 1: 2018 Solid Tumor Rules
Notes: Head and Neck, January 2019 Update
Solid Tumor Rules (2018)/Multiple Primaries--Head & Neck: How many primaries are accessioned and what M Rule applies when a patient is diagnosed with a right lateral tongue (C023) tumor in 2016 that was verrucous carcinoma (8051), followed by a new left tongue border (C021) tumor in 2019 that was squamous cell carcinoma, NOS (8070)? See Discussion.
According to the Multiple Primaries/Histology Rules in place at the time of the 2016 diagnosis, verrucous carcinoma was listed as a specific type of squamous carcinoma (Chart 1). However, in the current Solid Tumor Rules, verrucous carcinoma is not listed in Table 4 (Tumors of Oral Cavity and Mobile Tongue) either as a specific histology or as a specific subtype/variant of squamous carcinoma. The only subtype/variant listed for these sites is acantholytic squamous cell carcinoma (8075).
Verrucous carcinoma is not listed in Table 4, making it unclear if it should be a different histology for these specified sites. However, verrucous carcinoma is listed as a specific subtype/variant of squamous carcinoma for other sites (e.g., Table 3).
Accession a single primary based on the 2018 Head and Neck Solid Tumor Rule M13 as none of the other rules apply to the situation.
Not all histology codes are contained in the tables in the Solid Tumor Rules as they list the more common histologies. Verrucous carcinoma is a subtype of squamous cell carcinoma according to Table 3 of the Rules.
Solid Tumor rule tables are based on 4th Ed WHO Blue Books. Verrucous SCC is not included in oral cavity/mobile tongue chapter.