Histologic Features Associated with Lymph Node Metastasis in Stage T1 and Superficial T2 Rectal Adenocarcinomas in Abdominoperineal Resection Specimens: Identifying a Subset of Patients for Whom Treatment with Adjuvant Therapy or Completion Abdominoperineal Resection should be Considered After Local Excision

Abstract

Local excision of rectal adenocarcinomas that are confined to the submucosa is an accepted method of surgical excision. Adjuvant therapy and possibly completion abdominoperineal resection (APR) may be appropriate if lymph node (LN) metastases are present. Identifying the patients at high risk of having LN metastases would assist in disease management. We retrospectively examined 73 APR resection specimens with T1 or superficial T2 adenocarcinomas. The leading edge of the the tumor was evaluated for budding, microacinar structures, or isolated or small clusters of undifferentiated cells. The features were correlated with LN metastases. Eleven specimens had LN metastases. Extensive budding, microacinar structures, or undifferentiated cells, tumor grade 3, and small vessel vascular space invasion were associated with LN metastases. Limiting the comparison to grade I and 2 adenocarcinomas showed association of extensive budding, microtubular architecture, and undifferentiated cells along the advancing edge with LN metastases. If these histologic features are extensively present, the patient may be a candidate for adjuvant therapy or completion APR. The morphologic features of the advancing edge are independent of the tumor grade of the neoplastic glands within the body of the tumor; they can be incorporated into the evaluation of overall tumor grade.