Complete pathological response to pembrolizumab in pretreated pancreatic acinar cell carcinoma

Abstract

Background: Therapeutic approach used for pancreatic ductal adenocarcinoma is usually translated also for the rarer acinar counterpart, which shows a different mutational landscape nevertheless. While dMMR/MSI-H status is rare in the ductal histotype, it appears to be more prevalent in pancreatic acinar cell carcinoma (PACC).

Case presentation: We report the case of a patient with locally advanced MSI-H PACC in whom the treatment with the anti-PD-1 pembrolizumab, administered as third line, made possible surgical resection, achieving even an exceptional pathological complete response.

Conclusions: Treatment of PACC should be tailored based on the peculiar molecular features that distinguish PACC from ductal adenocarcinoma. Evaluation of potentially therapeutically targetable alterations should be mandatory in case of PACC diagnosis.

Keywords: Acinar cell carcinoma; Immunotherapy; Neoadjuvant therapy; Pancreatic cancer; Surgical resection; pCR.

Fig. 1

CT (A) and PET (B) scans at baseline

Fig. 2

Pathological features of the tumor. A–D cytologic specimen at the time of diagnosis; A Hypercellular cytologic smear (Hematoxylin–eosin rapid stain, original magnification 40X). B, D Cell block showing numerous neoplastic cell with round nuclei and eosinophilic cytoplasm; on the left normal pancreatic parenchyma (B Hematoxylin–eosin, original magnification 10X; C Bcl-10, original magnification 10X; D Synaptophysin, original magnification 10X). E–F: surgical specimen. E Tumor bed (Hematoxylin–eosin, original magnification 4X). F Lymph node with response to therapy (Hematoxylin–eosin, original magnification 2X). (magnification, × 20)

Fig. 3

CT scans after two lines of chemotherapy, before the start of pembrolizumab (A, B, C). CT scans after 3 months (D, E, F), after 6 months (G, H, I) and after 10 months (L, M, N) of pembrolizumab