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CHAPTER 109: Pancreas Allograft Pathology

Cinthia B Drachenberg; Megan L Troxell; John C Papadimitriou

GENERALITIES

Banff category 1: NORMAL PANCREAS ALLOGRAFT defined as absent or insignificant inflammation not involving ducts, veins, arteries, or acini. There is no graft sclerosis. The fibrous component is limited to normal septa and its amount is proportional to the size of the enclosed structures (ducts and vessels). The acinar parenchyma shows no signs of atrophy or injury (Figures 109-1 to 109-5).

FIGURE 109-1

Diagram representing normal pancreas parenchyma in a needle core biopsy. The bulk of the pancreas parenchyma is composed of exocrine acinar tissue arranged in lobules, separated by connective tissue fibrous septa (green areas). The delicate network of interacinar capillaries (black lines) is not evident on routine stains in normal tissue. The fibrous septa contain ducts, vessels, and nerves. Islets (light gray structure on the right) are distributed unevenly in the parenchyma and are occasionally absent in a needle core biopsy.

An illustration of the normal pancreas parenchyma in a needle core biopsy. The structure is formed horizontally by the use of small acinar tissues arranged in lobules. Small scattered gray lines are visible that indicate interacinar capillaries. Vertical septal collagen is seen near the left corner. An oval-shaped artery and a duct are present with the collagen. An inverted U-shaped vein is present at the bottom corner of the collagen. Two other septal collagens are also visible within the tissues. A set of tissues are colored gray along the right bottom corner.
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FIGURE 109-2

Routine hematoxylin and eosin (H&E)-stained pancreas allograft biopsy. Several thin fibrous septa are present, one of which is more prominent and contains a duct and small ductal branches. In the normal acinar lobules, the individual acini are tightly packed together with minimal intervening connective tissue. The normal septal connective tissue is paucicellular (with few nuclear profiles evident on routine stain) and appears mostly pink.

A micrograph of a patient for pancreas allograft biopsy. An oval-shaped duct and small ductal branches are present in between numerous fibrous septa.
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FIGURE 109-3

This image also demonstrates the normal pancreatic architecture. Very thin fibrous septa intersect the lobular tissue. Note scattered islets of Langerhans as slightly paler round structures (lower center and left).

A close view shows a vertical thin fibrous septum along the right side. A cluster of islets of Langerhans with light purple cells is shown.
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FIGURE 109-4

The lobular tissue is composed of multiple acini that appear solid, although each acinus has a lumen (the lumina are inconspicuous in normal acini). The cytoplasm of acinar cells is brightly pink and granular due to their abundant secretory vesicles (pancreatic exocrine products). The normal acinar tissue lacks inflammation and fibrosis.

A close view highlights multiple acni of a lobular tissue. Each acinus has a lumen and the cytoplasm appears dark pink on a dark purple background.
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FIGURE 109-5

In addition to H&E staining, pancreas allograft biopsies are routinely evaluated with a stain for collagen (Masson trichrome stain). In this sample, the connective tissue is highlighted in green. Note that the periphery of the exocrine lobules is smooth and the edges are often rounded. There is minimal amount of connective tissue between lobules, but within the lobules the acini are tightly packed together with no appreciable connective between them. A duct is identified in a septal area (center).

A close view shows long vertical connective tissues between lobules. The tissues are highlighted in green. The edge of the exocrine lobule is round.
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Banff category 2: INDETERMINATE defined as septal inflammation that appears somehow active, but the overall features do not fulfill the criteria for mild T-cell–mediated acute rejection (Figure 109-6).

FIGURE 109-6

Septal inflammation that does not fulfill the criteria for acute T-cell-mediated allograft ...

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