Diffuse Appearance of Red Bone Marrow on MRI Mimics Cancer Metastasis and Might be Associated with Heavy Smoking

Abstract

Background: Red bone marrow develops early in life and converts into yellow bone marrow with aging. Reconversion occurs when yellow bone marrow reconverts into red bone marrow due to increased oxygen demands. Objective: Diffuse appearance of red bone marrow on Magnetic Resonance Imaging (MRI) is rarely encountered. Materials and Methods: Seven patients, five male and two female, with the diffuse appearance of red bone marrow were evaluated. The average age was 71.4 (47-86) years old. All patients had been referred based on a working diagnosis of cancer metastasis. All patients were eventually rediagnosed with bone marrow reconversion. Results: Spinal MRI was evaluated in all patients, including the whole spine in four patients and lumbar spine in three patients. Six patients had slight anemia or close to the lower limit of normal hemoglobin (within 1mg/dl). Six patients were heavy smokers, having more than 20 cigarettes per day. Four patients had a history of stomach or bladder cancer (2 cases each). MRI revealed red bone marrow with a diffuse appearance and low signal intensity on T1- and T2-weighted images. Compared with the spinal cord/conus, the red bone marrow appeared isointense in about half of the cases, and in the other cases, the intensities were either slightly high or low. The signal of yellow bone marrow was isointense with the retroperitoneal fat. Conclusion: Diffuse red marrow can be difficult to differentiate from cancer metastasis. Compared to the MRI, signal intensity of the cord/conus is useful in the diagnosis of red marrow. Slight anemia may also be present. Heavy smoking might be related to the appearance of diffuse red marrow.