Acinar cell carcinoma of the pancreas showing finger-print-like zymogen granules by electron microscopy: immunohistochemical study

Abstract

A rare case of finger-print-like zymogen granules shown by electron microscopy is reported. The patient was a 75-year-old man who was histologically and ultrastructurally confirmed to have acinar cell carcinoma of the pancreas. Frozen section and postmortem examination revealed that the tumor was made up of solid nests of cells resembling the appearance of normal pancreatic acini, showing polygonal cells which had round or oval nuclei, and rare mitotic figures. Zymogen-like granules, shown by eosinophilic granular staining, were abundant in the cytoplasm. Electron microscopy showed that the tumor cells were closely packed, occasionally forming small intercellular spaces resembling pancreatic acini (microtubules). The cytoplasm contained characteristic zymogen granules with dark-to-medium electron density, measuring 660 nm +/-213 SD in diameter. The granules of medium density were large, and showed finger-print-like patterns. Investigation of more cases is necessary to identify whether these finger-print-like patterns are an important factor in the genesis of acinar cell carcinoma.

Acinar cell carcinomas with exophytic growth and intraductal pancreatic duct invasion: peculiar multislice computed tomographic picture

“…The immunohistochemical study from the general endocrine markers chromogranin and synaptophysin, and the pancreatic exocrine enzyme markers trypsin and chymotrypsin is absolutely essential for the correct diagnosis in some cases. [9] Identification of finger‐print‐like zymogen granules by electron microscopy may be helpful in the differential diagnosis [7]. ACCs are negative or focally positive for endocrine markers such as synaptophysin, insulin, glucagons, and serotonin [4, 5].…”

“…The diagnosis of ACC is mainly based on histological features such as acinar arrangement, ultrastructural demonstration of zymogen granules, immunostaining for exocrine pancreatic products (trypsin, chymotrypsin, lipase, phospholipase A2, and pancreatic stone protein), and occasional secretion of lipase into the serum [1, ]. Histologically, ACCs are sometimes difficult to differentiate from well‐differentiated endocrine tumors, especially those with a solid and partly trabecular pattern.…”

Acinar cell carcinoma of the pancreas eroding the pylorus and duodenal bulb

“…6 Toyota et al 13 reported that finger-print-like zymogen granules detected by electron microscopy could be an important factor in the genesis of ACC. 13 Resection is usually selected for the treatment of ACC. An unresected patient has poor prognosis.…”

“…Large electron‐dense granules are identified in the tumor by electron microscopy, and neuroendocrine secretory granules may also be found 6. Toyota et al13 reported that finger‐print‐like zymogen granules detected by electron microscopy could be an important factor in the genesis of ACC 13…”

Acinar cell carcinoma of the pancreas

“…The exact nature of these structures is not clear, although they resemble the earliest zymogen granules encountered in the developing fetal pancreas [57] . Toyota et al [58] indicated that finger-print-like zymogen granules detected by electron microscopy could be an important factor in the genesis of ACC.…”