Liver and intrahepatic bile ducts - tumor
Dysplasia
Macroregenerative nodule (MRN)

Author: Naziheh Assarzadegan, M.D. (see Authors page)
Editor: Raul S. Gonzalez, M.D.

Revised: 8 August 2017, last major update July 2017

Copyright: (c) 2003-2017, PathologyOutlines.com, Inc.

PubMed Search: Macroregenerative nodule [title]
Cite this page: Macroregenerative nodule. PathologyOutlines.com website. http://pathologyoutlines.com/topic/livertumormacroregenerativenodule.html. Accessed October 22nd, 2017.
Definition / general
  • Discrete regenerative hepatocellular nodule that often arises in the background of cirrhosis
Essential features
  • May represent a precursor of hepatocellular carcinoma (Hepatology 1992;16:949)
  • Classified into type I and type II, based on cytological and architectural atypia (Cancer 1998;61:99)
    • MRN II shows atypical cytologic or architectural features that are insufficient for a diagnosis of malignancy
Terminology
  • Also called hepatocellular pseudotumor, adenomatous hyperplasia, adenomatous hyperplastic nodule or adenomatous regeneration
Clinical features
  • Most MRNs are seen in cirrhotic livers
  • Occurs in about 10% of cirrhotic livers at autopsy or at time of transplantation
  • The role of MRN in hepatocarcinogenesis varies in different studies and the true biologic nature of these nodules is uncertain (Int J Hepatol 2016;2016:4390434)
Radiology description
  • Well defined isointense nodules relative to the background liver
Gross description
  • Usually multiple, large, discrete, tumor-like hepatocellular masses > 1 cm in diameter (rarely > 5 cm)
  • Often differ from surrounding nodular parenchyma in color, texture or degree to which they bulge beyond the cut liver surface
Gross images

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Macroregenerative nodules in explanted liver

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Macroregenerative nodule with atypical features

Microscopic (histologic) description
  • Liver cell plates 1 - 2 cells thick, reduced and scattered portal tracts with variable structural distortion (prominent bile ductules, absent interlobular bile ducts)
  • Hepatocytes resemble those in adjacent liver and may reflect any disease process there
  • MRN type II may have architectural and cytologic atypia
Microscopic (histologic) images

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Macroregenerative nodule with thickened hepatic plates

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Atypical macroregenerative nodule

Differential diagnosis
Board review question #1
    Which of these liver lesions is the least likely to arise in the background of cirrhosis?

  1. High grade dysplastic nodule
  2. Large regenerative nodule
  3. Low grade dysplastic nodule
  4. Macroregenerative nodule
Board review answer #1
B. Large regenerative nodule