The microwave tissue coagulator (MTC) is used in hepatectomy because it provides excellent haemostasis during the procedure. A 59 year old man underwent partial hepatic lobectomy with MTC, for metastasis from colon cancer. A tumorous necrotic nodule was discovered in the liver. The nodule measured 2.5 cm at its largest diameter. Microscopically, it showed extensive coagulation necrosis and massive sinusoidal dilatation. To date, such a necrotic mass clinically mimicking neoplasm has not been reported as a complication of hepatectomy using MTC. Although it is unknown how the rounded necrotic nodule was formed in this case, clinicians should be aware of this phenomenon to avoid unnecessary operations. Likewise, pathologists should recognise such histological changes and review the clinical history of the patient when coagulation necrosis with massive sinusoidal dilatation is observed in a biopsy or hepatectomy specimen.