A Report of Bone Marrow Metastasis of Colon Cancer as a Primary Diagnosis, Supported by Cytokeratin Immunohistochemical Staining

ABSTRACT

Bone marrow metastasis of colon cancer is rare. Here, we report a 56-year-old female patient who presented with pancytopenia. She was diagnosed with colon cancer accompanied by lung and axial skeleton metastasis. The bone marrow study showed metastatic carcinoma. Immunohistochemical (IHC) staining with anti-cytokeratin 7 (CK7) and anti-cytokeratin 20 (CK20) antibodies showed that the bone marrow samples were negative for CK7 and positive for CK20, consistent with metastatic colon cancer. To the best of our knowledge, there has been only one other reported case of bone marrow metastasis of colon cancer as the primary diagnosis in an adult patient in Korea. Bone and bone marrow metastases of colon cancer are regarded as uncommon. However, for proper management, bone marrows should be promptly examined in patients with solid tumors when unexplained cytopenia is noted, even if the origin of the tumor is known to be rarely metastatic to bone marrow. In addition, the use of cytokeratin IHC staining is helpful for determining the origin of metastatic carcinoma.