Lipomatous neoplasms

Question 1

Molecular alterations in a lipoma

Answer 1

HMGA1 or HMGA2 rearrangement

Question 1

Molecular alterations in angiolipoma

Answer 1

PRKD2 mutations (>80%)
More rarely, activating PIK3CA mutations

Question 2

Molecular alterations in chondroid lipoma

Answer 2

t(11;16) translocation with fusion of C11orf95 and MRTFB (myocardin-related transcription factor B)

Question 3

Molecular alterations in myelolipoma

Answer 3

WWTR1 translocations and alterations - clonal in both the adipocytic and myeloid elements.
(Also in epithelioid hemangioendothelioma! Composite neoplasms have been described)

Question 4

Molecular alterations in lipoblastoma

Answer 4

HAS2-PLAG1 and COL1A2-PLAG1
(Like pleomorphic adenoma, these also stain positive for PLAG and

Question 5

Molecular alterations in hibernoma

Answer 5

Structural rearrangements of 11q13

Question 6

Molecular alterations in well-differentiated liposarcoma / atypical lipomatous tumor

Answer 6

MDM2 and CDK4 amplification

Question 7

Molecular alterations in dedifferentiated liposarcoma

Answer 7

12q14 amplification, MDM2 and CDK4 amplification

Question 8

Molecular alterations in myxoid liposarcoma

Answer 8

FUS-DDIT3 fusion
Less commonly, EWSR1-DDIT3 fusion
(IHC is basically always DDIT3 positive)

Question 9

Molecular alterations in pleomorphic liposarcoma

Answer 9

Complex karyotype, but no specific alterations

Question 10

Answer 10

Chondroid lipoma

Question 11

Answer 11

Lipoblastoma

Question 12

Answer 12

Hibernoma

Question 13

Answer 13

Well-differentiated liposarcoma / Atypical lipomatous tumor

Patchy pink collagen in bands, large and small adipocytes, atypical/pleomorphic cells in the collagenous areas, lipoblasts

Lipoblasts may be seen, but are NOT required. The hyperchromatic, pleomorphic cells are the real hallmark cells of liposarcoma.

Sometimes they do just look like a lipoma though – so if it is over 10 cm, just do FISH

Question 14

Answer 14

Dedifferentiated liposarcoma

You can see your well-diff and your transition to de-diff

Question 15

Answer 15

Pleomorphic lipoma

aka spindle cell lipoma

RB1 lost, CD34 diffusely staining, MDM2 retained, benign

Question 16

Answer 16

Myxoid liposarcoma

DDIT3 positive

Question 17

Answer 17

Pleomorphic liposarcoma

Question 18

Answer 18

Myelolipoma

Question 19

Answer 19

Angiolipoma