Collision tumor versus multiphenotypic differentiation: a case of carcinoma with features of colonic and lung primary tumors.

BACKGROUND

Collision tumors are rare tumors composed of two histologically distinct neoplasms coinciding at the same location. Collision tumors need to be distinguished from tumors originating from a progenitor cell with potential for multiphenotypic differentiation.

CASE REPORT

A clinically puzzling case of an intricate malignant pulmonary nodule in a patient with previous history of colorectal carcinoma is reported. A brief review of the clinical literature on collision tumor and tumor stem cells is presented.

CONCLUSION

This case report emphasizes the importance of detailed histopathologic and immunohistochemical analyses, and clinical history in diagnosing a tumor composed of multiple malignant morphologies.