#1: Solid Tumor Rules (2018)
#3: Head & Neck
Source 1: 2018 Solid Tumor Rules
Notes: Head and Neck, Updated July 2019
Solid Tumor Rules (2018)/Histology--Head & Neck: How is histology coded for a glossotonsillar sulcus tumor with both squamous cell carcinoma and mucoepidermoid carcinoma? See Discussion.
Patient had a radical pharyngectomy showing a glossotonsillar sulcus tumor with high grade squamous cell carcinoma and adjacent high grade mucoepidermoid carcinoma. The pathologist commented, the tumor is composed of high grade mucoepidermoid carcinoma and high grade conventional-type squamous cell carcinoma that are immediately adjacent to one another. Given that the tumors are arising so close together and could represent a single neoplastic process with divergent morphologies, they are staged together.
Employing Solid Tumor Manual Rule M1 (single primary if unable to determine if there is a single or multiple tumors), it was determined that this should be reported as a single tumor because the pathologist referred to the case as both a tumor singular and tumors pleural. However, the Solid Tumor Manual Histology Rules for a Single Tumor do not appear to have an instruction for coding this histology combination.
Abstract multiple primaries using 2018 Head and Neck Solid Tumor Rule M8 as these are separate tumors described as arising close together, and are on different rows in Table 3. Code histology separately as squamous cell carcinoma (8070/3) and mucoepidermoid carcinoma (8430/3).
This appears to be a collision tumor. Collision tumors are counted as two individual tumors for the purpose of determining multiple primaries. Collision tumors were originally two separate tumors that arose in close proximity. As the tumors increased in size, they merged or overlapped each other. While more common in the colon, they can occur in other sites as well.