Atypical acinar cell foci in human pancreas: Morphological and morphometric analysis

Conclusion. The morphological and quantitative findings of the present study suggest that atypical acinar cell foci are not neoplastic in nature. Background. Atypical acinar cell loci (AACF) are rare and unusual lesions in the human pancreas. The biological nature of AACF is poorly understood, and is not clear whether they represent neoplastic or degenerative changes in the acinar cells. Methods. To further characterize and understand the significance of AACF in relation to acinar cell tumor development, we have examined these lesions by light and electron microscopy and evaluated the growth pattern by measuring cell proliferation and the size of the loci in the pancreas of a 16-yr-old male. Results. The pancreas was grossly unremarkable, AACF were randomly distributed throughout the pancreas, well delineated, and showed minimal variation in sizes. The constituent cells contained uniform nuclei, pale vacuolated cytoplasm, and exhibited low nuclear-cytoplasmic ratio. Electron microscopic examination showed a few zymogen granules and markedly dilated rough endoplasmic reticulum. Proliferative index in AACF (13%) was less than in adjacent uninvolved acinar tissue (19%). Quantitative stereological analysis showed the pancreas to contain approximately 1800 AACF/cm³ with a mean focal diameter of 360 μn.