Soft Tissue: Practice Question

Pleomorphic lipoma is considered a benign lesion, while atypical lipomatous tumor, also known as well-differentiated liposarcoma, has malignant potential. Which of the following is true in distinguishing these entities?
  1. MDM2 amplification in atypical lipomatous tumor
  2. Atypical cells
  3. CD34 positive cells in atypical lipomatous tumor
  4. Floret cells
  5. Ropey collagen found in atypical lipomatous tumor
Show Answer and Explanations

MDM2 amplification in atypical lipomatous tumor — Correct answer

Correct. Atypical lipomatous tumors have elongation of chromosome 12 and amplification of the MDM2 gene.

Atypical cells

Incorrect. Both of these lesions have atypical cells.

CD34 positive cells in atypical lipomatous tumor

Incorrect. Pleomorphic lipoma commonly has CD34 positive cells, and atypical lipomatous tumor rarely has CD34 positive cells.

Floret cells

Incorrect. Both of the lesions can have floret cells. Pleomorphic lipoma almost always has floret cells, and atypical lipomatous tumor sometimes has them.

Ropey collagen found in atypical lipomatous tumor

Incorrect. Ropey collagen is useful for distinguishing these entities, but it is found in pleomorphic lipoma.

Summary

Summary: Atypical lipomatous tumor shows an expanded chromosome 12 with MDM2 amplification. Pleomorphic lipoma is CD34 positive, more commonly has floret cells, and ropey collagen.
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