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Small Animal Pathology (Spring 2016) > L6: Path. Of The Lymphoid System (Abbott) > Flashcards

L6: Path. Of The Lymphoid System (Abbott) Flashcards

1
Q

Causes of INCREASED thymic size

A

Thymic lymphoma
Thymoma (and paraneoplastic syndromes)
Thymic brachial cysts
Thymic hematoma

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2
Q

Embryonic origin of thymus

A

Pharyngeal pouches 3/4

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3
Q

What type of organ is the thymus**

A

Lymphoepithelial:**

1) cortex for T-cell development and maturation
- lymphocytes, epithelial cells

2) Medulla for Ag presentation
- ep. Cells (Hassall’s corpuscles), dendritic cells, myoid cells

*can have lymphoma or thymoma

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4
Q

Fxs of thymus

A
  • develop T-lymphocytes that arrive as precursors from bone marrow
  • induce self-tolerance (thymic education)
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5
Q

Severe Combined Immunodeficiency (SCID)

A
  • causes thymic hypoplasia
  • Bassets and Corgis have defective function but mature cells**
  • Jack Russells have the inability to generate lymphocytes
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6
Q

Causes of thymic ATROPHY

A

1) Involution (normal aging)
2) Lympholysis:
- viruses replicate in lymphoid tissues (parvo, distemper, panleuk)
- steroids cause T cell death
- nutritional: Acrodermatitis, zinc deficiency, starvation
- toxic: PCBs

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7
Q

Thymic hypoplasia and lymphoid atrophy –> clinically?**

A

IMMUNOLOGIC DYSFUNCTION:

  • get sicker or more often than expected
  • difficult to dx
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8
Q

CS of INCREASED thymic size

A

(Space-occupying)

  • dyspnea, cough
  • regurge
  • edema, swollen head and neck
  • chylothorax
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9
Q

Chars. Of thymoma***

A
  • tumors derived from the EPITHELIAL COMPONENT of the thymus**
  • neoplastic, NOT viral
  • adult animals
  • mets and invasion is NOT common (unlike lymphoma)***
  • SPACE-OCCUPYING biggest problem
  • encapsulated, anterior mediastinal mass
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10
Q

Paraneoplastic syndromes assoc. with thymomas

A
  • Acquired autoimmune disorders: myasthenia gravis, polymyositis
  • Exfoliative dermatitis
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11
Q

Diffusely pale, cystic, bulging “fish flesh” thymus, fairly homogenous in color

A

Thymoma (key clue: CYSTIC)

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12
Q

Thymoma is a tumor of the ___ component of the thymus***

A

Epithelial

-can have normal lymphs which can outnumber neoplastic cells

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13
Q

Lymphoma is a tumor of ____***

A

Lymphocytes/lymphoblasts

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14
Q

Clinical course of thymic lymphoma

A
  • pleural effusion
  • aggressive, invasive*
  • neoplastic lymphs in the pleural cavity*
  • middle aged to older dogs
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15
Q

Feline thymic lymphoma

A
  • young, FeLV+ cats most common

- usually no involvement of other organs except bone marrow

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16
Q

Thymic Branchial cysts lined and filled by:

A

FIlled with mucoserous fluid, lined by ciliated, columnar epithelial cells

  • develop from vestiges of fetal branchial arch system
  • space-occupying mass
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17
Q

Causes of thymic hemorrhage/hematoma

A 
Trauma
Bleeding disorders (ie. Rodenticide)
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18
Q

Lymph node structure

A
  • dynamic and changing depending on immune status

- cells and fluid moving constantly

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19
Q

Fxs of LN

A
  • filtration of lymph from dependent areas
  • capture infectious agents and foreign material
  • localize immune response: process and present foreign Ag
  • house lymphs, macs, and other Ag-presenting cells
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20
Q

Which LN are palpable only when enlarged?

A

Facial
Retropharyngeal
Iliac

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21
Q

Df for lymphadenomegaly

A

Hyperplasia
Inflammation (lymphadenitis)
Neoplasia

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22
Q

Lymph Node HYPERPLASIA**

A
  • proliferation of lymphocytes due to Ag stimulation*
  • node architecture is maintained**
  • tan, homogenous, fish flesh**
  • usually large immature lymphoblasts and small mature lymphocytes +/- increased plasma cells and/or macrophages
  • Causes: Salmon poisoning, FIV
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23
Q

Gross appearance of lymphadenitis**

A

Swollen, gray-red, painful, may abscess

24
Q

Chars. Of lymphadenitis**

A
  • lymphocyte hyperplasia + inflammatory cells (neuts, macs) and fibrin**
  • node is actually involved in the process, not just draining an affected site
  • can spread to adjacent nodes
25
Q

Causes of decreased thymic size

A

Hypoplasia

Atrophy

26
Q

Spleen fxs

A
  • host immune response
  • filtration via phagocytosis
  • hematopoiesis
  • reserve blood storage
27
Q

Problems of the spleen

A
  • splenomegaly
  • splenic masses
  • splenic rupture
  • splenic torsion
  • hypersplenism (rare)
  • vague, non-specific signs
28
Q

Reasons to remove spleen

A

-rupture
-torsion
-neoplasia
Symptomatic splenomegaly
-autoantibodies to RBCs or platelets

29
Q

Causes of splenomegaly

A
  • neoplasia
  • vascular: hematoma, congestion, infarct
  • nodular hyperplasia
  • diffuse hyperplasia
  • splenitis
30
Q

Primary splenic tumors

A
  • HSA
  • Lymphoma
  • Leiomyosarcoma
  • Hemangioma
  • MCT (cats)
31
Q

Which splenic neoplasias make single masses?

A

Leiomyosarcoma
Hemangioma
HSA can be single or multiple nodular

32
Q

Which splenic neoplasia makes diffuse masses in the SP?

A

Myeloid leukemia
MCT
Lymphoma (diffuse or nodular)

33
Q

Hematoma can mimic HSA

A
  • single nodule
  • exudes blood
  • clotted blood +/- organization
34
Q

What can cause splenic congestion?

A
  • Pentobarbital
  • R sided heart failure
  • portal hypertension
  • splenic torsion
35
Q

Gross appearance of nodular hyperplasia of the spleen

A

-smooth, red or tan, nodular, bulging

36
Q

What is nodular hyperplasia?

A

Hyperplastic lymphoid elements plus congestion

-mimics HSA

37
Q

Diffuse hyperplasia (SP)

A
  • spleen is “activated” to remove abnormal or opsonized cells or microbes from circulation
  • diffuse non-friable enlargement grossly
  • EMH is a regenerative response
38
Q

Splenitis

A
  • diffuse enlargement 2ary to any blood-borne infection
  • nodular or multinodular
  • abscess or granulomas +/- lymphoid hyperplasia
39
Q

Relative prevalence of splenic disease in dogs

A

Nodular hyperplasia/hematoma > HSA > LSA > other neoplasias

40
Q

Relative prevalence of splenic disease in cats

A

MCT or LSA > leukemia > hyperplastic nodules/HSA > hematomas

41
Q

Outcomes of splenic rupture**

A
  • Acute: Fatal internal hemorrhage**

- Chronic: healing which may produce notches, fissures, divisions, accessory spleens

42
Q

Siderotic plaques***

A
  • DOGS only
  • very common senile change on the capsule of the SP
  • mineralization caused by hemorrhage into capsule of the spleen that gets phagocytized
  • incidental finding
43
Q

Accessory/ectopic spleens

A
  • CATS more common
  • omentum most common location
  • hard to distinguish from HSA mets
44
Q

White/tan nodules on the spleen most likely:

A

Nodular hyperplasia

45
Q

Forms of canine lymphoma

A

1) Multicentric** (80%)
2) Alimentary
3) Mediastinal - rare
4) Cutaneous - mycosis fungoides
5) Leukemic (majority of animals with solid tumors do NOT have detectable neoplastic cells in the peripheral blood**)

46
Q

Difference b/w staging and grading tumors

A

Staging: where the tumor is
Grading: histologic nature of the tumor (ie. T vs. B cell lymphoma)

47
Q

Dx of lymphoma

A
  • Gross: LN soft, fish flesh, homogenous
  • Cytology: homogenous population, high mitotic index
  • Biopsy: effacement of normal architecture*** (invasion of capsule and perinodal tissue, filling of subcapsular sinus w/ tumor cells)
48
Q

Hypercalcemia of malignancy

A
  • Hypercalcemia due to pseudohyperparathyroidism from lymphoma
  • tumor produces PTH-like substance
  • CS: PU/PD due to Ca inhibition of ADH, ST mineralization
49
Q

Most common neoplasm of cats

A

Feline Lymphoma

50
Q

Chars. Of feline lymphoma

A
  • 10-20% FeLV+
  • middle aged cats
  • Forms:
    1) alimentary (most common)
    2) mediastinal (young kittens, FeLV+)
    3) multicentric
    4) solitary (usually kidneys or CNS)
    5) cutaneous (rare)
51
Q

Ddx for lymphoma in the nasal cavity

A
  • cryptococcus

- adenocarcinoma

52
Q

Ddx for multicentric lymphoma

A

FIP

Systemic fungal infection

53
Q

2 plasma cell tumors

A
  • Multiple myeloma

- Solitary plasmacytoma

54
Q

Multiple myeloma

A
  • in bones w/ active hematopoiesis
  • causes lytic bone lesions, monoclonal gammopathy
  • poor prognosis
55
Q

Solitary plasmacytoma

A
  • location: digits, ears, lip
  • NOT assoc. with serum Ig elevation
  • excision usually curative

Small Animal Pathology (Spring 2016) (3 decks)

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