First Report and 3D Reconstruction of a Presumptive Microscopic Liver Lipoma in a Black Barbel (Barbus balcanicus) from the River Bregalnica in the Republic of North Macedonia

Abstract

A lipoma is a benign tumour of mature adipocytes which may appear in various species, including marine and freshwater fish. It usually occurs in isolated locations, such as a superficial or deep mass, mainly in the skin and seldom in other organs. In non-mammalian vertebrates, there is no agreed minimal size for the mass to be considered a lipoma. This study histologically describes a case proposed to be a microlipoma in the liver of Barbus balcanicus. The structure was an oval-shaped mass of well-differentiated adipocytes, surrounded by hepatic parenchyma. The adipocyte cluster did not contact with major vascular or biliary tracts, the liver capsule, or the hilum. The cell mass reached a maximal linear length and width of ~0.5 mm and ~0.4 mm. A three-dimensional and software-assisted reconstruction of the adipocytic mass showed that it had the shape of a flattened prolate spheroid (~0.01 mm3). Given the histological criteria currently used in the literature, we consider the mass as a lipoma, or, better, a microlipoma because it was tiny. We interpret this structure as an early growing lipoma. This work is the second description of a liver lipoma in a fish to the best of our knowledge.

Special Issue on the Histopathology of Aquatic Animals

“…Three published manuscripts used histopathological methodology to investigate tissues of interest on various cyprinid fish from ecosystems of the Balkan Peninsula. The case study of lipoma found in the liver of the black barbel (Barbus balcanicus) in the Bregalnica River (North Macedonia) was described by Rebok et al [14]. This agglomerate of adipocytes was assessed microscopically after being serially sectioned, while the authors also reconstructed a 3D image after applying software.…”

Occurrence of hepatic and splenic lipomas in Nile tilapia (Oreochromis niloticus)

“…In most cases, lipomas are solitary and are located subcutaneously, or intramuscularly. However, localized lipomas have also been reported in organs such as kidney and liver (Rebok et al, 2021). Lipomas have even been observed in the spleen of perch (Stejskal et al, 2016).…”