MCC is a rare, aggressive neuroendocrine tumor that is usually found in the dermis and can extend into the subcutaneous tissue or involve the overlying epidermis [4]. Patients with distant metastasis have a poor prognosis due to the high propensity for local recurrence and distant metastasis [5]. Median overall survival with MCC was 3.6 years for local disease, 2.0 years for regional disease, and 1.2 years for distant metastasis in multicenter cohort study [6]. This is the first case of long survival of more than 5 years after hepatectomy for liver metastasis of MCC without recurrence.
Gastroenteropancreatic neuroendocrine tumor is generally classified by mitotic count and Ki-67 labeling index (Ki-67 LI), according to the WHO 2010 classification. Some researcher recently suggested that the higher Ki-67 LI might be associated with unfavorable oncological outcome [7]. In this study, the Ki-67 LI of primary MCC was 2.1% and that of liver metastasis was 26.0%. This result suggests two important implications. First, primary MCC with lower Ki-67 LI can develop metastasis. Second, the complete resection for liver metastasis may contribute to the long survival, even if the tumor has high Ki-67 LI.
MCC sometimes develops metastasis to the lymph nodes, kidney, small bowel, pancreatic body, adrenal glands, abdominal wall, bone marrow, and parathyroid glands [2]. The frequency of liver metastases is relatively rare [8], and patients with liver metastasis of MCC rarely have a chance undergoing hepatectomy. Skagias et al. reported a case that underwent extended right hepatectomy for the liver metastasis of MCC, 15 cm in diameter, which is the only report of hepatic resection for liver metastasis of MCC [9]. They provided no data of the prognosis after hepatectomy. The current metastatic tumor of the liver was solitary, and the maximum diameter of the liver tumor was 15 mm. It is difficult to make any definite comments; however, the current results suggest that patients with small and solitary metastatic liver tumor of MCC may achieve long-term survival following hepatic resection, and hepatic resection may be justified for these patients. Thus, careful examination of the liver is important after primary resection of MCC, and early detection of the liver metastasis of MCC is crucial.
The typical chemotherapeutic regimens of MCC are similar to those for small cell lung cancer and neuroendocrine tumors in other locations [1,10]. The optimal chemotherapy regimen for patients with MCC remains controversial, although most authors have prescribed combination chemotherapy regimens [8]. Some common regimens include cisplatin with etoposide, cytoxan with adriamycin and vincristine, cisplatin with adriamycin, and streptozocin with 5- fluorouracil [11,12]. The reported median survival time from initiation of chemotherapy for distant metastasis of MCC is approximately 9 months [5,13]. The current patient received chemotherapy with cisplatin and etoposide for 12 weeks, beginning 6 weeks after hepatectomy for liver metastasis of MCC. Although the current patient received chemotherapy according to the previous report [11], MCC was initially thought to be resistant to chemotherapy. In recent study, it was suggested that treating with adjuvant chemotherapy was not associated with improved MCC outcomes in large cohort [6]. On the other hand, in some previous reports, adjuvant radiation therapy plays a significant role in MCC treatment by reducing recurrence and improving local/regional control of disease [3,14,15]. Moreover, some authors mentioned that neoadjuvant chemotherapy led to local control and allowed curative surgery [16], resulting in long-term survival, whereas the clinical results of these therapies cannot be verified without long survivors. We think that a curative surgery with enough margins is the best choice contributing to improvement of the outcome, and further prospective study with neoadjuvant and adjuvant therapy will be needed.
