L4: Mesenchymal Neoplasia (Beatty)

Question 1

Benign mesenchymal neoplasia ends in:

Answer 1

-oma

Ie. Fibroma, lipoma

Question 2

Malignant mesenchymal neoplasia ends in:

Answer 2

-sarcoma

Ie. Osteosarcoma, Soft tissue sarcoma

Question 3

How do mesenchymal tumors met?

Answer 3

Hematogenously (typically)

-usually go to LIV, SP first

Question 4

Mesenchymal cells form:

Answer 4

Connect tissue, blood vessels, lymphatics

-originate in soft tissue, bone, and cartilage

Question 5

Selected mesenchymal neoplasms

Answer 5

• lipoma/liposarcoma
• scar tissue/reactive fibroplasia
• equine sarcoid
• soft tissue sarcoma
• hemangiosarcoma
• synovial cell sarcoma
• osteosarcoma

Question 6

Chars. Of lipoma

Answer 6

• common SC tumor in dog
• less commonly IM or infiltrative
• do NOT transform into liposarcomas*
• slides appear oily
• aspirated material may wash off fixative
• appearance: variable # of adipocytes and strung out stromal cells; small nuclei can be smushed to the side
• adipocytes can’t be differentiated from normal SC fat*

Question 7

Chars. Of liposarcoma

Answer 7

• uncommon tumor in older dogs
• spindle-shaped cells w/ features of malignancy
• lipid rich background
• predilection for ventrum and extremities
• feel firmer than lipomas

Question 8

Chars. Of scar tissue/reactive fibroplasia

Answer 8

• mesenchymal cells w/ variable atypia
• often inflamed
• histopath often needed to differentiate from neoplasia

Question 9

Chars. Of Equine sarcoids

Answer 9

• common cutaneous tumor in horses
• char. By atypical mesenchymal cells
• Ddx: granulation tissue, sarcoid, fibrosarcoma
• assoc. with bovine papilloma virus*
• needs histopath for dx

Question 10

Types of soft tissue sarcomas

Answer 10

• perivascular wall tumors
• fibrosarcoma
• myxosarcoma
• peripheral nerve sheath tumors

Question 11

Chars. Of perivascular wall tumors

Answer 11

• formerly called “hemangiopericytoma”
• originates from vascular pericytes, myopericytes
• common mesenchymal tumor in dogs
• common on lateral surface of extremities

Question 12

Cytologic char. Of perivascular wall tumors

Answer 12

• extremely cellular
• anaplastic mesenchymal cells w/ very wispy cytoplasm
• small punctate cytoplasmic vacuoles
• 1-2 prominent nucleoli per cell
• cells branch off capillaries
• multinucleated cells w/ peripheral nuclei (crown cells)

Question 13

Chars. Of fibrosarcoma

Answer 13

• occur in older animals
• may be assoc. with injections in cats (rabies most common)
• firm, variable exfoliation
• absence of inflammation (center may be necrotic and inflamed)
• locally infiltrative and aggressive
• must get wide sx excision +/- radiation!
• slow to met usually

Question 14

Cytologic chars. Of fibrosarcomas

Answer 14

• low to moderate # individually arranged cells
• spindle-shaped w/ malignancy chars. (Ie. Coarse chromatin, nucleolus larger than RBC, high N:C
• pink eosinophilic fibrillar matrix around cell clumps
• absence of inflamm.

Question 15

Histopath of soft tissue sarcomas

Answer 15

• typically not differentiated
• graded on 1+ to 3+ scale based on differentiation, mitotic rate, and necrosis
• grade predictive of metastasis and possible local recurrence**

Question 16

Chars. Of hemangiosarcoma

Answer 16

• older, large breeds
• sites: SP, LIV, R atrium, retroperitoneal space, bone, dermal
• assoc. with collapse, hemoabdomen, fragmentation hemolysis (shistocytes, keratocytes, ecchinocytes), thrombocytopenia, DIC
• endothelial cell (blood vessel) origin

Question 17

Cytologic chars. Of hemangiosarcoma

Answer 17

• large atypical pleomorphic cells w/ pale blue cytoplasm with colorless punctate vacuoles
• variable exfoliation
• many samples hemodilute

Question 18

Chars. Of synovial cell sarcoma

Answer 18

• CT neoplasm arising from cells in the synovial membrane
• sites: elbow, stifle, shoulder of large breeds
• difficult to distinguish b/w histiocytic sarcoma and SCS
• locally invasive, may cross the joint, 25% met

Question 19

Cytologic chars. Of synovial cell sarcomas

Answer 19

• granular eosinophilic background (mucin)
• dual pop. Of anaplastic mesenchymal cells that are oval w/ eccentrically placed nuclei and spindle-shaped
• large angular, irregular nuclei
• mitotic figures

Question 20

Which neoplasias have mucinous backgrounds on cytology?

Answer 20

Synovial cell sarcomas
Myxosarcomas
Chondrosarcomas

Question 21

Histiocytic sarcoma

Answer 21

• neoplasm of joints

- common in Rottweiler, stifles

Question 22

Synovial myxoma

Answer 22

• neoplasm of joint

- Dobermans, stifles

Question 23

General chars. Of tumors of bone and cartilage

Answer 23

• may arise from any tissue in bone, mesenchymal cells of osseous or cartilaginous origin, or vascular or CT cells
• many malignant in dogs
• felines and equines may be benign
• includes osteomas and chondromas

Question 24

Chars. Of osteosarcoma

Answer 24

• most common malignant bone tumor of the limbs
• looks similar to round cell tumor
• appendicular forms typically in giant or large breeds
• uncommon in cats
• sites: away from elbow, toward the knee
• rapid hematogenous spread
• 90% have mets by time of dx! (LU)
• ones on axial skeleton may be less aggressive and are more common in small dogs
• feline OS more common on femur and are less aggressive w/ reduced incidence of mets

Question 25

Cytologic appearance of osteosarcoma

Answer 25

• looks like round cell tumor
• large oval to spindle shaped cells
• individually arranged
• variably distinct cytoplasmic borders
• eccentric nuclei*
• MNGCs
• dense amorphous pink material = osteoid

Question 26

Ddx for lytic proliferative bone lesion

Answer 26

Osteosarcoma
Fungus
Multiple myeloma

Question 27

General characteristics of mesenchymal neoplasms

Answer 27

• variable exfoliation
• cells individually arranged
• indistinct, wispy cytoplasmic borders
• spindle-shaped, fusiform, stellate cells
• nuclear features CAN be reliable indicator for most
• histopath can be needed for muscle and cartilagenous tumors (ie. Leiomyoma)