False-positive blood pooling adjacent to hepatic malignant fibrous histiocytoma on Tc-99m RBC liver SPECT

A 40-year-old woman with right upper quadrant abdominal fullness and pain underwent Tc-99m RBC liver SPECT. A hot area of increased blood pooling immediately adjacent to a photopenic mass in the right lobe of the liver was revealed. Microscopic examination of the resected liver tissue revealed primary malignant fibrous histiocytoma with adjacent focal sinusoidal dilatation. The increased activity was thought to result from blood pooling within the sinusoidal dilatation. This finding indicates that, when typical blood pooling suggesting a cavernous hemangioma is revealed on Tc-99m RBC liver SPECT, false-positive results derived from malignant diseases are possible.