A 68-year-old male presents with symptoms of anemia. On workup, you discover that the patient has been losing blood from the GI tract secondary to a tumor mass in his colon. The pathology repo from a biopsy specimen indicates that this mass is an invasive adenocarcinoma. Which one of the listed descriptions best describes the most likely histologic appearance of this tumor?

Malignant tumors are generally classified as being either carcinomas or sarcomas. Carcinomas are malignant tumors of epithelial origin, while sarcomas are malignant tumors of mesenchymal tissue. malignant epithelial tumors (carcinomas) include adenocarcinomas, which consist of a disorganized mass of malignant cells that form glandular structures, and squamous cell carcinomas, which consist of a disorganized mass of malignant cells that produce keratin. malignant mesenchymal tumors include rhabdomyosarcomas, leiomyosarcomas, fibrosarcomas, and liposarcomas. Reference: Robbins & Cotran Pathologic Basis of Disease, 9edition.