# An Extremely Rare Case of Coexisting Neuroendocrine Carcinoma and Tumor of the Whole Pancreas with Hepatoid Differentiation

## TL;DR

A 15-year-old girl with a rare pancreatic tumor combining neuroendocrine and hepatoid features showed partial response to chemotherapy but died due to liver metastases.

## Contribution

This paper reports the first case of coexisting neuroendocrine carcinoma and neuroendocrine tumor with hepatoid differentiation in the whole pancreas.

## Key findings

- The patient showed partial response to chemotherapy, leading to tumor shrinkage and conversion surgery.
- Despite surgery, liver metastases worsened, and the patient died within 10 months.
- Elevated serum AFP levels were observed, indicating aggressive tumor behavior.

## Abstract

Hepatoid carcinoma (HC) is a rare type of malignant tumor that shares similar serological, morphological, and immunohistochemical features with hepatocellular carcinoma. Pancreatic HC exhibits aggressive biological behavior and is classified as pure type, combined type, and mixed type. Unlike the pure type, the combined and mixed types refer to HC with other histological components. While the most common component is the neuroendocrine tumor (NET), no case of coexistence of neuroendocrine carcinoma (NEC) and NET with hepatoid differentiation has been reported. We herein report an extremely rare case of coexisting NEC and NET of the whole pancreas with hepatoid differentiation.

A 15-year-old woman had epigastric pain and impaired glucose tolerance, without any medical or family history. Computed tomography (CT) revealed a 6.4-cm mass in the pancreatic head, an enhanced mass throughout the pancreas, and a 1.0-cm liver lesion. Positron emission tomography (PET)/CT and somatostatin receptor scintigraphy (SRS) suggested a NET in the pancreatic body and tail, and a NEC in the pancreatic head. Biopsies confirmed NEC in the pancreatic head and liver with possible hepatoid differentiation. The patient underwent combination chemotherapy with carboplatin and etoposide. Due to the partial response achieved with chemotherapy, which led to significant tumor shrinkage on CT and no uptake on PET/CT in the pancreatic head tumor, the patient proceeded with conversion surgery, including a total pancreatectomy with portal vein resection and partial hepatectomy. However, serum α-fetoprotein (AFP) levels rapidly rose, and multiple liver metastases of NEC were detected on CT at 5 months after surgery. Liver metastases worsened despite further chemotherapy. The patient died 10 months after surgery.

We herein present an extremely rare case of coexisting NET and NEC of the whole pancreas with hepatoid differentiation. Due to a remarkable response to chemotherapy, conversion surgery was performed. However, early recurrence of liver metastases accompanied by a rapid increase in serum AFP levels occurred, and the prognosis was poor. Pancreatic HC should be considered when encountering a bulky tumor of the pancreas with elevated serum AFP levels, and further case series and analysis are needed to determine the appropriate treatment strategy.