Pathology: lipoma

Lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • Aggregates of foamy macrophages often present

  • Often associated with HMGA2-rearrangement; many potential partners, including LPP

Lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with mild variability in size and shape

  • Peripherally located small monomorphic nuclei

  • FISH: MDM2 non-amplified

Lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • FISH: MDM2 non-amplified

Lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

Lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • FISH: MDM2 non-amplified

Lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • Hypocellular collagenous septa

  • Focal fan necrosis with histiocytic infiltrate

  • FISH: MDM2 non-amplified

Lipoma with fat necrosis

  • Polygonal cells arranged in sheets and lobules

  • Ghost outlines of cells with hyalinized membranes

  • Dystrophic calcification

  • Histiocytic infiltrate typically present

Intramuscular lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • Entrapped skeletal muscle fibers may show atrophy, which should not be confused with atypia of liposarcoma

  • Often associated with HMGA2-rearrangement; many potential partners, including LPP


Intramuscular lipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • Entrapped skeletal muscle fibers may show atrophy, which should not be confused with atypia of liposarcoma

  • FISH: MDM2 non-amplified

Fibrolipoma

  • Polygonal cells arranged in sheets and lobules

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • Interspersed dense paucicellular fibrous septa, which should not be confused with the spindle cells and ropy bands of collagen of spindle cell lipoma


Osteolipoma

  • Sheets of adipocytes

  • Abundant clear cytoplasm with minimal variability in size and shape

  • Peripherally located small monomorphic nuclei

  • Nodules of metaplastic bone; fibrous septa may be broad, but paucicellular