Histiocytic Sarcoma

Question 1

LC expresses what?

Answer 1

-E-cadherin

Question 2

Interdigitating DCs are present in what locations?

Answer 2

-LNs and spleen

Question 3

What are migratory DCs?

Answer 3

-They are langerhan cells and interstitial DCs; cannot phagocytose but important in antigen presentation to lymphocytes

Question 4

HS vs reactive histiocytosis IHC

Answer 4

• HS: CD1b+, CD1c, CD11c+, CD18+, MHCII+, Thy-1(+/-)-rarely
• Reactive histiocytosis (CH/SH): E-cadherin negative but positive for all (CD1, CD4, CD11c, CD11d, CD18+, MHCII+, and Thy-1 (CD90)+

Question 5

From what cell does histiocytoma arise from?

Answer 5

-LC (aka. intraepidermal DAPCs); E-cadherin positive and Thy-1 (negative), CD4- and CD11d-

Question 6

Canine reactive histiocytosis (RH) is readily distinguished from cutaneous histiocytoma by:

Answer 6

a. Angiotropism and Thy-1 expression*
b. Epitheliotropism and MHCII expression
c. Predilection for extremities, scrotum and face; CD1a, CD1b and CD1c expression
d. Late stage LN involvement; expression of E-cadherin
e. Infarction of surrounding tissues; consistent CD11d expression

Question 7

Canine hemophagocytic histiocytic sarcoma is best defined by expression of:

Answer 7

a. CD1
b. MHCII
c. D11b
d. CD11d*
e. Thy-1

Question 8

Canine hemophagocytic sarcoma is putatively derived from?

Answer 8

a. Interdigitating dendritic cells
b. Follicular dendritic cells
c. Splenic red pulp macrophages*
d. Langerhans cells
e. All of the above

Question 9

What are the cells of origin for reactive histiocytosis?

Answer 9

-Activated interstitial DCs

Question 10

What is the clinical differentiation between CH (cutaneous histiocytosis) and SH (systemic histiocytosis)?

Answer 10

CH primarily involves the skin and subcutis and does NOT go beyond local draning LNs

Question 11

What is the predilected breed for cutaneous histiocytomas?

Answer 11

-Shar peis

Question 12

. Feline progressive histiocytosis – histopathology, markers

Answer 12

• Histopathology: composed of non-phagocytizing monomorphic histiocytes variably admixed with neutrophils and small mature lymphocytes
  
  • IHC markers: CD1a, CD1c, CD11b, CD18 and MHC II positive; co-expresion of E-cadherin was only noted in a few cats
    
    • CD1 analysis is mandatory to confirm dendritic cell origin

Question 13

What are the predisposed breeds for HS?

Answer 13

-Flat coated retrievers (localized), Rotties, Bermese mountain dogs (polygenic mode of inheritance) and
Labrador retrievers

Question 14

What hematologic abnormalities can be found in dogs with HS?**

Answer 14

• Cytopenias
  
  • Coagulation abnormalities—indicative of DIC
  • Hyperbilirubinemia
  • Hyperferritinemia

Question 15

What is the overall response rate for canine with DSH treated with CCNU? Median survival time?

Answer 15

-ORR: 46% with a median survival time of 6 months

Question 16

What are the common hematologic abnormalities seen with hemophagocytic HS?

Answer 16

• Thrombocytopenia
  
  • Regenerative anemia
  • Hypoalbuminemia
  • Hypocholesterolemia