Evaluation of the Vulvar Cancer Histology Code Reported by Central Cancer Registries: Importance in Epidemiology

Abstract

Context.—Knowing the subtype of vulvar cancer histology is important for estimating human papillomavirus–related cancer etiology. Surveillance of human papillomavirus–related vulvar cancers informs public health decisions related to vaccination against human papillomavirus. Objective.—To assess the accuracy of registry classifications of vulvar cancer and determine the histologic classification of cases reported as not otherwise specified. Design.—Pathology specimens were collected from Florida, Iowa, and Hawaii cancer registries. Registry diagnosis was compared with the pathology report from the medical record and a single expert study histology review of a representative histologic section from each case. Results.—The study included 60 invasive vulvar squamous cell carcinoma (SCC) cases, 6 Paget disease cases, 2 basal cell carcinoma cases, and 53 in situ cases. Comparing subtypes of invasive vulvar SCC, the registry agreed with the pathology report classification in 49 of 60 cases (81.7%). Study histology review identified the same SCC subtype as the registry in 9 of 60 cases (15.0%) and the same SCC subtype as the pathology report in 11 of 60 cases (18.3%). Whereas the registry and pathology reports classified 37 and 34 cases, respectively, as being SCC not otherwise specified, the study histology review identified a more specific subtype in all cases. Conclusions.—Subtypes of vulvar cancer were frequently recorded as not otherwise specified in the cancer registry primarily because the pathology report often did not specify the histologic subtype. Vulvar cancer registry data are useful for tracking broad diagnostic categories, but are less reliable for vulvar cancer subtypes.