Multistep, multicentric, and simultaneous development of hepatocellular carcinoma.

We resected a multiple hepatocellular carcinoma (HCC) which contained portal tracts, showed evidence of an early multistep condition, and a multicentric development of HCC which progressed simultaneously. A preoperative working examination revealed a tumor in S5 of the liver, which was 2.5 cm in diameter. In addition, a "nodule-in-nodule" appearance was seen on the ultrasonographic imaging. At intraoperative ultrasonography, an additional two HCCs were detected. At histologic examination of the resected specimen, the main nodule showed a nodule-in-nodule appearance. In the outer nodule, there was a well-differentiated HCC, while the portal tracts remained. The less-differentiated HCC grew in the inner nodule and was replacing the well-differentiated HCC in the outer nodule. These findings suggests morphological transition in the early stages of the multistep development of HCC. Two additional tumors (1.1 cm and 1.0 cm in diameter) detected at intraoperative ultrasonography proved to be HCCs (grade I) with marked fatty change, and with portal tracts remaining within both the HCCs. Furthermore, both of the HCCs retained their preexisting liver structure. These histologic findings coincided with the characteristics of the early stage HCC, whereas the coexistence of early stage HCCs suggests the multicentric development of HCC. Distortion, compression, and invasion of the portal tracts may appear as the tumor grows, thereby evoking an increasing risk of metastasis via the portal tracts. Therefore, the early diagnosis and treatment of HCC before the portal tracts disappear, when 1.5 cm in size or less, may be very important for surgeons and diagnosticians, as an effective curative resection may be feasible.