NEC versus NET G3—is there a grey zone? Case report of pancreatic NET G3 with rapid disease progression

Patients with well-differentiated neuroendocrine tumors of grade 3 (NET G3) exhibit a significantly better survival than patients with poorly differentiated neuroendocrine carcinomas (NEC). However, some cases of NET G3 with high Ki-67 index present with highly aggressive clinical behavior, prompting the question whether there are selected tumors representing a biological continuum between NET G3 and NEC.

Here we report the case of a 49-year-old man with pancreatic NET G3 metastasized to the liver. Surgery was not indicated, and the patient was initially treated with cisplatin/etoposide on account of the high proliferation rate (Ki-67 index of 50%). Restaging showed immediate disease progression with new liver metastases, so therapy with capecitabine/temozolomide was initiated and continued until progressive disease after 7 cycles. Comprehensive diagnostic evaluation, including functional imaging and genetic analyses, revealed no potential therapeutic targets, and further treatment options were limited. The patient died shortly after a therapeutic attempt with streptozotocin/5-fluorouracil.

This case exemplifies the unfortunate course of a rapidly progressive NET G3 and highlights the limited number of effective therapies for some tumors within the relatively new cohort of NET G3 with a yet unsatisfactory understanding of its underlying tumor biology and behavioral spectrum.