Medullary adenocarcinoma of the colon: Clinicopathologic study of 11 cases

Colonic carcinomas with minimal or no glandular differentiation are a heter ogeneous group of neoplasms which differ in their histologic appearance, cl inical features, prognosis and molecular characteristics. Since 1990, we pr ospectively identified 11 patients with a predominantly solid (nonglandular ) adenocarcinoma of the colon for which the term medullary adenocarcinoma o f the colon (MAC) is proposed. The clinical, histological, histochemical, a nd immunohistochemical features of these neoplasms were studied. All patien ts with MAC were women with tumors in the cecum or proximal colon. Histolog ical analysis showed nests or trabeculae of regular small to medium-sized c ells with moderate amounts of eosinophilic cytoplasm; some cells contained mucin vacuoles. The nuclei had an open chromatin pattern and exhibited prom inent nucleoli. Lymphatic permeation was present in most cases. Immunohisto chemical reactions were positive for cytokeratin, carcinoembryonic antigen, and epithelial membrane antigen, Despite its histological resemblance with endocrine tumors, MAC is negative for endocrine markers. Of the eight pati ents for whom follow-up is available, four patients (two Dukes B and two Du kes C) are alive and well 1 to 4 years after surgery, one patient (Dukes C) died of tumor, one patient is alive with liver metastasis 4 years after su rgery, and two patients died in the postoperative period. MAC appears to be a distinctive clinicopathologic entity. This tumor should be distinguished from other more aggressive, nonglandular tumors of the colon. Copyright (C ) 1999 by W.B. Saunders Company.