Soft Tissue Tumours

Question 1

What clinical scenario can result from phosphaturic mesenchymal tumour?

Answer 1

Tumour induced osteomalacia

Question 2

What tumour can cause tumour induced osteomalacia?

Answer 2

Phosphaturic mesenchymal tumour

Question 3

What is the mechanism of tumour induced osteomalacia in phosphaturic mesenchymal tumour?

Answer 3

Production of FGF23 which is a phosphaturic hormone that inhibits renal proximal tubule phosphate reuptake, leading to severe hypophosphatemia

Question 4

What enzyme is produced in phosphaturic mesenchymal tumour?

Answer 4

FGF23

Question 5

What is the cell of origin/differentiation of phosphaturic mesenchymal tumour?

Answer 5

Uncertain differentiation

Question 6

What is the molecular basis of phosphaturic mesenchymal tumour?

Answer 6

Fusion of FN1-FGFR1 or FN1-FGF1 (rarely), leading to production of FGF23

Question 7

What does FGF23 stand for?

Answer 7

Fibroblast growth factor 23

Question 8

What processes is fibroblast growth factor 23 involved in?

Answer 8

Phosphate and vitamin D metabolism and regulation

Question 9

Where does phosphaturic mesenchymal tumour occur?

Answer 9

Soft tissue and bone

Question 10

Where does phosphaturic mesenchymal tumour usually not occur?

Answer 10

Retroperitoneum/viscera/mediastinum

Question 11

Who does phosphaturic mesenchymal tumour usually occur in?

Answer 11

Middle aged adults

Question 12

What proportion of phosphaturic mesenchymal tumours bear a characteristic gene fusion?

Answer 12

Almost 50%

Question 13

What marker is expressed in most phosphaturic mesenchymal tumours regardless of fusion status?

Answer 13

FGFR1

Question 14

FGFR1 is expressed rarely in phosphaturic mesenchymal tumour, true or false?

Answer 14

False (common, regardless of fusion status)

Question 15

What are the possible macro appearances of phosphaturic mesenchymal tumour?

Answer 15

Non-specific, with calcs, with fat

Question 16

What tumour features: - bland spindled fibrohistiocytic cells - smudgy hyaline matrix - capillary network with possible stag horn vessels with pericytoma features - grungy/flocculent calcs, maybe slate grey flower like crystals - primitive cartilage or osteoid - osteoclasts - fat - microcystic change - peripheral shell of woven bone - no mitosis or necrosis usually

Answer 16

Phosphaturic mesenchymal tumour

Question 17

What are the histologic features of phosphaturic mesenchymal tumour?

Answer 17

• bland spindled fibrohistiocytic cells - smudgy hyaline matrix - capillary network with possible stag horn vessels with pericytoma features - grungy/flocculent calcs, maybe slate grey flower like crystals - primitive cartilage or osteoid - osteoclasts - fat - microcystic change - peripheral shell of woven bone - no mitosis or necrosis usually

Question 18

Are phosphaturic mesenchymal tumours benign or malignant?

Answer 18

Benign (but can have malignant ones)

Question 19

What are the features of malignant phosphaturic mesenchymal tumour?

Answer 19

High grade nuclear features, invasion, recurrence (look like undiff pleomorphic sarcoma or fibrosarcoma)

Question 20

What does this image show? Which tumour is it characteristic of?

Answer 20

Grungy calcifications in phosphaturic mesenchymal tumour