Chapter 13: Langerhans Histiocytosis + Spleen and Thymus Flashcards

1
Q

Most common mutation in Langerhans Cell Histiocytosis?

A

Valine-to-glutamate substitution at residue 600 in BRAF (same as Hairy Cell Leukemia)

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2
Q

Characteristic morphological finding of the Langerhans Cells in histiocytosis?

A

Birbeck granules in cytoplasm (Tennis racket-like)

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3
Q

Tumor cells of Langerhans Cell Histiocytosis typically express what 3 markers?

A

HLA-DR, S-100, and CD1a

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4
Q

Multifocal multisystem Langerhans cell histiocytosis (Lettere-Siwe disease) most often occurs in whom; characterized by what?

A
  • Children <2 y/o
  • Seborrheic eruptions of trunk and scalp + osteolytic bone lesions
  • Hepatosplenomegaly + LAD + pulmonary lesions
  • Anemia, thrombocytopenia and reuccrent infections, such as otits media and mastoiditis
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5
Q

Prognosis of multifocal multisystem Langerhans cell histiocytosis (Lettere-Siwe disease)?

A

Untreated = rapidly fatal; with intense chemo 50% survive 5 years

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6
Q

What are the characteristic findings of unifocal unisystem Langerhans cell histiocytosis (eosinophilic granuloma)?

A
  • Skeletal lesions in older children, rarely adults
  • Most common in the calvarium, ribs, and femur –> pathologic fractures
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7
Q

What are the characteristic findings of multifocal unisystem Langerhans cell histiocytosis (eosinophilic granuloma)?

A
  • Multiple erosive bony masses in young child
  • 50% have diabetes insipidus
  • Hand-Schuller-Christian triad: calvarial bone defects, diabetes insipidus, and exopthalmos
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8
Q

What is course of unifocal and multifocal unisystem Langerhans cell histiocytosis (eosinophilic granuloma); how is each treated?

A
  • Many patients experience spontaneous regression
  • Chemotherapy if multifocal
  • Local excision or irradiation if unifocal
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9
Q

Pulmonary Langerhans histiocytosis is most often seen in whom; characteristics?

A
  • Most often in adult smokers
  • Multiple fine nodules and cysts in the middle and upper lung zones
  • May regress after cessation of smoking
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10
Q

Which benign neoplasms are the most common in the spleen?

A
  • Hamartomas
  • Hemangiomas
  • Lymphangiomas
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11
Q

Major morphological feature of nonspecific acute splenitis?

A

Acute congestion of the red pulp, may efface the lymphoid follicles

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12
Q

What is seen in hypersplenism and it’s often due to what?

A
  • Becomes ↑ active –> anemia, leukopenia, and thrombocytopenia
  • Often seen in setting of splenomegaly, but is most common 2’ to portal HTN and hematologic disorders
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13
Q

What are the 3 most common causes of congestive splenomegaly?

A
  • Cirrhosis of liver = most common; alcoholics or schistosomiasis
  • Portal or splenic vein thrombosis
  • Cardiac failure; especially right-sided
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14
Q

Characteristic morphology of the spleen in long-standing congestive splenomegaly?

A
  • Organ is firm and capsule is thickened and fibrous
  • Red pulp becomes fibrotic over time
  • Resultant slowing of blood, prolongs exposure of blood cells to macrophages, resulting in excessive destruction (hypersplenism)
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15
Q

What are common causes of occlusion of splenic arteries by emboli leading to splenic infarction?

A
  • Cardiac emboli and sickle cell disease
  • May occur in infectious endocarditis
  • Splenomegaly, regardless of cause
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16
Q

Which congenital anomaly of the spleen is common; significance?

A
  • Accessory spleen(s)
  • Important to recognize in diseases with splenectomy as tx, such as hereditary spherocytosis and ITP
17
Q

Most common causes of splenic rupture?

A
  • Most often due to blunt trauma
  • Predisposing conditions = infectious mononucleosis, malaria, typhoid fever, and lymphoid neoplasms
  • Rupture leads to intraperitoneal hemorrhage
18
Q

What is clinical significance of cytic thymic lesion in symptomatic pt?

A

Should provoke thorough search for neoplasm, particularly a lymphoma or thymoma

19
Q

Why is thymic hyperplasia a misleading term, what does it actually refer to?

A
  • Appearance of thymic lymphoid follicles containing predominantly B-lymphocytes; thymus is typically normal size
  • Better term = thymic follicular hyperplasia
20
Q

Thymic follicular hyperplasia most often occurs in what setting?

A

Mysathenia Gravis

21
Q

Thymomas are tumors of which cells?

A

Thymic EPITHELIAL cells usually set against background of non-neoplastic T cells (known as thymocytes)

22
Q

Majority of thymomas arise in which location?

A

Anterosuperior mediastinum

23
Q

What are some of the presenting sx’s and associated disorders with Thymomas?

A
  • Common sx’s due to impingement on mediastinal structures
  • Some present in pt’s with Myasthenia Gravis
  • Associated neoplastic disorders: hypogammaglobulinemia, pure red cell aplasia, Graves disease, pernicious anemia, dermatomyositis-polymyositis, and Cushing syndrome
24
Q

By definition, invasive thymomas do what?

A

Penetrate through capsule into surrounding structures

25
Q

Which variant of thymic carcinoma is most common and what is the next most common?

A
  • Squamous cell carcinoma = most common
  • Lymphoepithelioma-like = 2nd most
26
Q

Which variant of thymic carcinoma is associated with EBV?

A

Lymphoepithelioma-like

27
Q

How does invasive thymoma (type 1) differ from thymic carcinoma (type 2); most often contains which type of epithelial cells?

A
  • Cytologically bland but biologically aggressive
  • Cortical-typeepithelial cells =polygonalw/roundtooval, blandnuclei
28
Q

Benign (encapsulated) non-invasive thymomas are most often composed of what type of epithelial cells?

A

Medullary-type = elongated and spindle-shaped