Higher Ki67 Index, Nodal Involvement, and Invasive Growth Were High Risk Factors for Worse Prognosis in Conventional Mammary Analogue Secretory Carcinoma

Abstract

The prognostic factors of salivary (mammary analogue) secretory carcinoma (SC) are unclear because of the rarity of the tumor. This report presents the largest case series to investigate the prognosis-related clinicopathologic factors in conventional SC. This study was based on a retrospective cohort study from 1993 to 2015 of patients whose sections were reviewed and who were newly diagnosed as having SC by the detection of ETV6 rearrangement. Clinicopathologic features, including age, gender, involvement site, tumor category, node category, histopathologic subtype, cellular atypia, tumor necrosis, growth pattern (noninvasive vs invasive), perineural invasion, margin, hyalinized fibrous septa, Ki67 expression, and postoperative treatment, were analyzed as primary predictors. Patients' final outcomes-including no evidence of disease, recurrence, metastasis, and death-were collected during follow-up. Survival analysis was performed only for conventional SC using the Kaplan-Meier method and the Cox proportional hazards regression model. Sixty-two cases of SC were retrospectively confirmed. Fifty-nine cases were identified as conventional SC, whereas 3 cases were identified as high-grade SC. In conventional SC, univariate analyses showed that nodal metastasis, invasive growth, and a Ki67 index of at least 10% were related to decreased recurrence-free survival (RFS), distant disease-free survival (DDFS), and disease-free survival (DFS). Age older than 44years, T3 and T4 stages, and markedly hyalinized fibrous septa were associated with decreased DDFS. T3 and T4 stages, positive margins, and tumor necrosis were associated with decreased overall survival. By multivariate analysis, the Ki67 index was found to be an independent prognostic factor for RFS (P=.008) and DFS (P=.003). Although most patients with conventional SC had a favorable clinical prognosis, patients with nodal involvement, invasive growth, and a Ki67 index higher than 10% showed a poor clinical outcome by exhibiting local recurrence or distal metastasis. Patients with a higher Ki67 index especially need close observation for local recurrence.