Automated feathered edge blood smear analysis: early diagnosis of carcinocythemia in a case of disseminated intravascular coagulation with multi-organ failure.

Carcinocythemia, known as the presence of circulating tumor cells in the peripheral blood, is difficult to detect when the carcinoma cells are minimally present. We describe a case of a 56-year-old patient presenting with disseminated intravascular coagulation (DIC) and multiple organ failure. Despite initial suspicion of sepsis, a peripheral blood smear showed the presence of atypical cells, mainly located at the feathered edge, leading to a presumptive diagnosis of carcinocythemia of unknown primary origin. The presence of a high-fluorescent cell population detected by our hematology analyzer (Sysmex XN-9100) and immunohistochemical staining with pancytokeratin AE1/AE3 confirmed the carcinoma cell origin. The patient died 4 days after referral to our hospital. Postmortem examination revealed a pleomorphic lobular breast carcinoma (triple-negative, androgen receptor-negative). Given the clinical acuity of patients with carcinocythemia, early diagnosis is essential to guide management. This case underscores the importance of optimizing current workflows relying on complex flagging algorithms and enhanced digital imaging to aid in the early detection of such rare condition. When patients present with DIC of unknown origin and high fluorescent signals are detected on the hematology analyzer, carcinocythemia should actively be ruled out by extensive microscopic peripheral blood examination.