Plexiform lesions of soft tissue

Question 1

Answer 1

Plexiform fibrohistiocytic tumor

Nodular with numerous giant cells

Question 2

Answer 2

Plexiform fibrohistiocytic tumor

Well circumscribed with a mixed population

Question 3

Answer 3

Plexiform fibrohistiocytic tumor

Fibroblastic variant

Question 4

Answer 4

Cellular neurothekeoma

Epithelioid predominant

Question 5

Answer 5

Cellular neurothekeoma

Epithelioid to spindled

Question 6

Answer 6

Cellular neurothekeoma

Collagenous

Question 7

Answer 7

Dermal nerve sheath myxoma

Question 8

Answer 8

Plexiform Schwannoma

Can you see the Verocay bodies? Here they are on higher power

Question 9

Answer 9

Plexiform Schwannoma

Interlacing fascicles of spindle cells in an Antoni A pattern

Question 10

Answer 10

Plexiform neurofibroma

Typical spindle tumor cells with indistinct cytoplasmic membranes and wavy nuclei embedded in a loose background

This is the most imporant one to recognize, since it is an MPNST precursor in patients with NF1

Question 11

Answer 11

Plexiform neurofibroma with myxoid change

Question 12

Stains to differentiate plexiform neurofibroma and plexiform Schwannoma?

Answer 12

S100 is key

Diffusely positive in Schwannoma,
focal/patchy positive in neurofibroma