Extreme thrombocytosis in a patient with ruptured colon cancer and iron deficiency anemia

Extreme thrombocytosis defined as a platelet count exceeding 1000∓10³/μL was most often thought to be due to clonal myeloproliferative disorders. Here we report a case of extreme thrombocytosis in a patient with colon cancer who had no evidence of myeloproliferative disorders. This 59-year-old woman presented with abdominal pain and extreme thrombocytosis of 1726 × 10³/ μL. Investigations disclosed recto-sigmoid cancer and iron deficiency anemia. Surgical exploration revealed the recto-sigmoid cancer was ruptured with surrounding abscess formation. Bone marrow examination showed no evidence of clonal myeloproliferative disorders. The platelet count returned to the normal range after surgical resection of the primary tumor and resolution of the abscess and the iron deficiency anemia. Eight months later, evidence of progression of multiple liver metastases was found, again accompanied by elevation of the platelet count to 639 × 10³/μL. After successful salvage chemotherapy with oxaliplatin plus high dose 5-FU and leucovorin, the platelet count returned to normal. We conclude that the combined effects of malignancy, abscess formation and iron deficiency contributed to the extreme thrombocytosis in this case. We suggest that a search for secondary causes is still required for a patient with a platelet count exceeding 1000 × 10³/μL.