Incidence patterns for myoepithelial carcinoma: a Surveillance, Epidemiology, and End Results (SEER) study

Xiaofei Zhang, Jiyi Hu, Jiade J. Lu, Jing Gao, Xiyin Guan, Lin Kong


Background: Myoepithelial carcinoma is a rare malignancy, and has been described only in case reports or small case series. Its patterns of incidence are largely unknown due to the rarity of the condition, thus hampering the effective development of its diagnosis and management. In addition, demographics and risk factors that affect myoepithelial carcinoma incidence reported from previous series conflict with each other. Here we aim to analyze a relatively extensive, population-based cancer registry to study the association between the incidence and patient age, gender, race, tumor location, and other factors to investigate incidence changes over the past decade.
Methods: Data were retrieved from the Surveillance, Epidemiology, and End Results (SEER) database from 1973 to 2012. Histological codes were used to determine myoepithelial carcinoma cases. Age-adjusted incidence-rates were compared by confidence intervals (CIs) in the SEER*Stat Version 8.2.1 program, while Joinpoint regression analysis was used to determine annual percentage changes and to locate substantial changes in incidence, respectively.
Results: Three hundred sixty-eight patients were identified from the SEER database. The observed incidence rate per 100,000 person-years was found to be significantly higher (P<0.05) in oral cavity/pharynx compared other sites, but did not differ with respect to gender and race of patients (males 0.013±0.002, females 0.013±0.002; white 0.011±0.001, black 0.020±0.005, or American Indian/AK Native/Asian/Pacific Islander 0.020±0.005). There was a significant difference in the primary location of the disease between adult and pediatric patients and between female and male patients (both P<0.05): children were more likely to harbor myoepithelial carcinoma in the soft tissues (including heart), whereas adults were more likely to develop the malignancy in the head and neck areas. Females were significantly more likely to develop myoepithelial carcinoma in the breast (26.8% vs. 0, Chi-square value =46.52, P<0.001), whereas in males it more commonly presented in the skin, (7.4% vs. 0.6%, Chi-square value =10.83, P=0.001) and oral cavity/pharynx (68.2% vs. 57.0%, Chi-square value =4.363, P=0.037). Between 2000 and 2012, the incidence increased significantly among male patients, which was 0.009 in 2000 and 0.058 in 2012, with an annual percentage change of 10.8 (P<0.05). However no increase was seen for females, with 0.007 in 2000 and 0.025 in 2012. After age adjustment, there were no rapid changes at any single year.
Conclusions: Both genders and different races have an equal overall incidence of myoepithelial carcinoma. Oral cavity/pharynx was the most common site. Children versus adult and female versus male comparisons display different site presentations. The incidence in males seems to have increased over the past decade; however, such phenomenon was not observed in females.