JPC SYSTEMIC PATHOLOGY

HEMOLYMPHATIC SYSTEM

February 2024

H-N03

 

 

SIGNALMENT (#4007069): Tissue from a 13-month-old female CD-1 mouse.

 

HISTORY: Sentinel mouse exposed to dirty bedding and aerosol exposure of potential pathogens. Gross necropsy findings include nodular splenomegaly, hepatomegaly, multiple intraabdominal masses, diffuse discoloration of the spleen and liver with beige foci, and beige discoloration of the kidney. 

 

HISTOPATHOLOGIC DESCRIPTION: Lymph node, renal: Diffusely effacing all lymphoid follicles, causing loss of the corticomedullary architecture, and infiltrating into the perinodal connective tissue is a non-encapsulated, well demarcated, densely cellular neoplasm composed of round cells often with spindled morphology, arranged in sheets on a preexisting fibrovascular stroma. Neoplastic cells have variably distinct cell borders, moderate to abundant amounts of pale, eosinophilic cytoplasm with round, oval, or reniform nuclei that contain clumped to marginated chromatin and one to two distinct nucleoli. Anisocytosis and anisokaryosis are moderate and there are occasional multinucleated cells. There are 4 mitotic figures per 2.37mm² and some are occasionally atypical.  

 

Kidney: Diffusely the cytoplasm of proximal convoluted tubular epithelial cells are filled with numerous 2-3 micron round, brightly eosinophilic droplets (hyaline droplets). Low numbers of scattered neutrophils, macrophages, lymphocyte, and plasma cells are present in the cortical interstitium.

 

Adrenal gland: Beneath the capsules there are multifocal dense aggregates of proliferative spindle cells arranged in streams that partially extend into the cortex (subcapsular spindle cell proliferation). At the corticomedullary junction there is a band of cells that have large amounts of vacuolated amphophilic cytoplasm and have multiple nuclei (X-zone involution).

 

Urinary bladder: No significant lesions.

 

MORPHOLOGIC DIAGNOSIS: 1. Lymph node, renal: Histiocytic sarcoma, CD-1 mouse, rodent.

2.   Kidney, proximal convoluted tubules: Intracytoplasmic hyaline droplets, diffuse.

3.   Adrenal gland: Spindle cell proliferation, subcapsular, multifocal, mild.

4.   Adrenal gland, corticomedullary junction: Epithelial cell vacuolation and degeneration, diffuse (X-zone involution).

5.   Urinary bladder: Normal.

 

CONDITION NAME: 1. Histiocytic sarcoma (HS)

2. Subcapsular spindle cell proliferation 

3. X-zone involution 

 

GENERAL DISCUSSION:  

• In mice, histiocytic sarcoma arises from mononuclear phagocytic cells such as Kupffer cells and tissue macrophages
• Histiocytes are all cells of dendritic cell (both nonlymphoid and lymphoid lineages) or macrophage lineage that differentiate from CD34+ stem cell precursors (myeloid DCs); all express CD18
  • Dendritic cell lineages (all express CD1a, MHC class I and II; activated dendritic cells express CD4):
    • Nonlymphoid DCs (most histiocytic diseases in domestic animals originate from this category and all express CD11c): 
      • Langerhans (epithelial) cells (LC) occur within epithelia/epidermis of the skin and alimentary, respiratory, and reproductive tracts
        1. Express E-cadherin, CD207 (langerin)
        2. Birbeck’s granules are found in the LCs of mice, humans, pigs, cats, and many others (but NOT dogs)
      • Interstitial DCs (express CD204) occur in perivascular locations in many organs (not the brain, but do occur in the meninges and choroid plexus); do not express E-cadherin
        1. Dermal interstitial DCs are specifically in the dermis and express Thy-1 (CD90)
    • Lymphoid DCs: Interdigitating dendritic cells of T-cell domains in lymphoid organs (e.g. spleen, lymph node)
  • Macrophages: All express CD11d and differentially express beta-2 integrins
    • In most tissues, macrophages express CD11b/CD18 
    • In hematopoietic sites, such as the splenic red pulp, bone marrow, and lymph node medullary sinuses, they express CD11d/CD18
    • Other macrophage markers include: Mac387 (calprotectin), CD163 & CD204 (scavenger receptors also expressed in interstitial DCs) and MHC class II

• Histiocytic sarcoma occurs in older mice with low incidence, except the following:

• B6 and SJL strains, in which it occurs as part of a multicentric disease involving the liver, mesenteric lymph nodes, and uterus
• Triple null mutant mice lacking Dok-1, Dok-2, and Dok-3, develop HS, but do not develop other types of tumors (Dok-1, Dok-2, and Dok-3 are negative regulators of  PTK-mediated proliferation and transformation of cells and are preferentially expressed on hematopoietic cells)

 

PATHOGENESIS:  

• Etiology and pathogenesis are unknown; produced experimentally using retroviruses or carcinogens in mice; based on IHC these neoplasms arise from mononuclear phagocytic cells (e.g. Kupffer cell) and tissue macrophages
• Pulmonary metastasis is common in mice with hepatic histiocytic sarcoma
• Lesions may be localized or disseminated to multiple organs (either via metastasis or from multicentric disease) 

 

TYPICAL GROSS FINDINGS:  

• White/cream to tan, homogenous mass or diffuse organ enlargement; single or multi-organ involvement common

• Variable; dependent on organ involved

• Spleen - Enlarged from extramedullary hematopoiesis
• Liver - Enlarged and mottled
• Uterus - Single, firm, white nodule in uterine wall
• Nodular involvement of the kidney, lungs, vagina, and ovaries also reported

• Organs most frequently affected (most frequent to least): spleen > various LN > liver > kidney > lung 

 

TYPICAL LIGHT MICROSCOPIC FINDINGS:  

•  Neoplastic cells of varying morphology, ranging from large round cells with macrophage–like or anaplastic features to fusiform, spindle–shaped cells with a fibroblastoid appearance occurring in intertwining bands or palisading patterns, either as pure populations or in mixtures of varying proportions

• Elongate cell pattern common in uterus 

• Randomly distributed nests of neoplastic cells in hepatic sinusoids, around vessels, and sometimes forming nodules 
• Abundant, foamy eosinophilic cytoplasm, indistinct cell borders with a basophilic pleomorphic nucleus
• Anisocytosis, anisokaryosis, and variable nuclear to cytoplasmic ratio are common
• Erythrophagocytosis (particularly in the liver), large nuclei and multinucleate giant cells are common features
• Splenic extramedullary hematopoiesis is induced by this neoplasm
• Kidney: Intracytoplasmic hyaline droplets within proximal tubular epithelial cells of the kidney occurs in 96% of histiocytic sarcoma cases in rats (Sprague-Dawley, Osborne-Mendel, Fischer 344) and in 55% of cases in mice (B6C3F1)

• Droplets are immunohistochemically positive for lysozyme but negative for 1-antitrypsin, alpha 2µ -globulin, immunoglobulin, and albumin 
• Malignant histiocytes secrete lysozyme which is ultimately filtered in the kidney and reabsorbed into proximal tubule epithelial cells resulting in accumulation
•  The process is reportedly independent of the hyaline droplet nephropathy involving alpha 2µ -globulin in the male rat

• Periarticular: Micronodular growth beneath intact synovium
• CNS: Originate in leptomeninges

 

ADDITIONAL DIAGNOSTIC TESTS:

• Positive for: CD18, CD 204, MHC II, lysozyme, MAC-2, F4/80, alpha-1 trypsin and alpha-1 chymotrypsin; +/- Cd163;
  • CD90 in cutaneous histiocytic sarcoma only
  • CD1a and CD11c in periarticular histiocytic sarcoma; interstitial dendritic cell phenotype; consistent with synovial type A cells
• Negative for CD4, E-Cadherin, CD3 and CD79a
• Assessment for clonal rearrangement of immune receptor genes (Ig heavy and light chains or TCRβ genes):  lymphoma will have clonal arrangement of one these genes and HS will have absence of clonal arrangement (germline configuration)

 

DIFFERENTIAL DIAGNOSIS:  

Microscopic:

• Lymphoma: Thymus is frequently involved
• Histiocyte-associated lymphoma (HAL): Diffuse large B cell lymphoma that features sheets of pink, fusiform to vacuolated histiocytes with large numbers of lymphocytes; more than half the cells may be lymphocytes; histiocytes are not considered neoplastic; frequently involves the liver; a retrospective immunohistochemical study determined only 33% of cases initially diagnosed as HS were determined to be HS; half of the remainder were determined to be HAL and the other were composites composed of lymphoma and HS
• Composite lymphoma and histiocytic sarcoma: Two concurrently neoplastic cell populations
• Fibrosarcoma 
• Granulomatous inflammation
• For uterine histiocytic sarcoma: Neoplastic cells have a spindle appearance that may mimic fibrosarcoma and leiomyosarcoma

 

 

COMPARATIVE PATHOLOGY: 

Rat: 

• Most common in Sprague Dawley rats but also seen in other strains
• In F344 and Sprague Dawley rats the liver and lungs are the most common sites, while the subcutis is the primary site in Wistar rats
• May resemble large granular lymphocytic leukemia (LGL) that is seen in F344, Wistar, and Wistar-Furth rats
• Hyaline droplets in the renal tubular epithelial cells

Dog: Immunohistochemical profile of each type is listed in the table below

Histiocytic proliferative disorders:

• Canine cutaneous histiocytoma (CCH): Benign neoplasm of epidermal Langerhans cell origin; spontaneous regression
  • Expresses: E-cadherin, CD1a, CD11a&c/CD18, CD44, CD45, and MHC class II
• Cutaneous Langerhans cell histiocytosis: (LCH) 
  • Typically presents as multiple cutaneous lesions; occasional lymph node and systemic metastasis (worse prognosis)
  • Histologically resembles CCH; similar immunohistochemical features; Shar-pei dog may be overrepresented
• Reactive histiocytosis: Non-neoplastic proliferation only reported in dog; likely dysregulation of activated dermal interstitial dendritic cells and CD8+ T-cells; often angiocentric and angio-invasive; positive for CD1a, CD11c/CD18, MCH class II, CD4 (marker of activated DCs), CD204, Thy-1 (CD90, marker for dermal DCs); negative for E-cadherin
  • Cutaneous reactive histiocytosis: 
    • More common
    • Single or multiple dermal nodules limited to skin and lymph nodes; “bottom-heavy”
  • Systemic reactive histiocytosis: 
    • Progression of cutaneous disease to involve internal organs
    • Young, middle aged, male Bernese mountain dogs
    • Cutaneous lesions often found in scrotum, nasal planum, and eyelids, and peripheral lymph nodes
    • Histopathology similar to cutaneous form
  • Antigen that drives the dysregulation is unknown but speculated it’s the T-cell via tumor necrosis factor-alpha and GM-CSF
• Histiocytic sarcoma: Neoplasm of interstitial dendritic cells positive for CD1a, MHC class II, and CD11c/CD18, but NOT CD4 and E-cadherin; ONLY cutaneous HS express CD90:
  • Bernese Mountain dogs and Flat-coated Retrievers have mutations of tumor suppressor gene loci CDKN2A/B, RB1, PTEN; other overrepresented dogs include: Golden retrievers, Labrador retrievers, and Rottweilers
  • Local histiocytic sarcoma: Rapidly growing dermal/subcutaneous nodules, often near joint (periarticular/articular HS)
    • Most common tumor in joints of dogs
    • Grossly multilobulated that fills the joint and extends into surrounding bones and tissue (“crosses the joint”)
    • Significant association between previous joint disease/trauma and peri-articular HS
    • Stifle & elbow are most commonly affected joints; rottweilers are overrepresented
    • CD1a, CD11c/CD18 positive 
    • Differential diagnoses in the dog:
      • Synovial sarcomas or soft tissue spindle cell sarcomas: Infiltrated by CD18 positive histiocytic cells may resemble HS; neoplastic population will be CD18 negative spindle cells
      • Spindle cell sarcoma with multinucleated giant cells: Previously referred to as malignant fibrous histiocytoma but neoplastic cells are negative for CD18 and CD204
  • Disseminated histiocytic sarcoma (previously: malignant histiocytosis): 
    • Unclear if it is metastasis of localized HS or multicentric malignant transformation of histiocytes
    • Fatal familial disease of older Bernese mountain dogs
    • Primary neoplasm in spleen, lung, bone marrow; +/- dissemination to liver, lymph nodes, brain (meninges), synovial tissues of limbs, rarely skin
    • Pleomorphic histiocytes; numerous multinucleated giant cells; widespread metastasis and rapid clinical progression
• Hemophagocytic histiocytic sarcoma: Neoplasm of splenic red pulp/bone marrow macrophages positive for CD1a, CD11d (beta 2-integrin) and CD18, negative for CD11c:   
  • Only malignancy of macrophage origin and occurs primarily in dogs
  • Primary non-mass forming neoplasm of the spleen, bone marrow; carries the worst prognosis of histiocytic sarcomas
  • Often intermixed with EMH and plasma cells
  • Erythrophagocytosis
  • Clinical pathology: resembles IMHA clinically; regenerative hemolytic anemia (no agglutination), leukopenia, and thrombocytopenia due to erythrophagocytosis; mild hyperbilirubinemia, hypoalbuminemia and often hypocholesterolemia

• Central nervous system HS: Rare
  • Usually originates in leptomeninges (may extend into the brain)
  • No metastasis beyond CNS reported
  • Positive for: CD1a, CD11c/CD18, MHC class II, Iba1 (ionized calcium binding adaptor molecule 1), CD163 & CD204 (scavenger receptors on macrophages, but a small subset of interstitial DCs have them too)
• Dendritic cell leukemia: Rare (2 reports in dogs)
  • Atypical histiocytes in peripheral blood; diffuse infiltration of affected organs (bone marrow, spleen, lung, and liver) without mass formation
  • Interstitial DC lineage: positive for CD1a, CD11c, MHC class II
    • Negative for CD11d

Felines:

            cats)

• Resembles a low-grade histiocytic sarcoma originating from cutaneous interstitial DCs; female > male; disease of mature cats
  • Solitary or multiple nonpruritic firm papules, nodules, and plaques with a predilection for head, feet, legs and face that later involves internal organs
  • Positive for CD1a, CD11c/CD18, MHC class II; E-cadherin negative; interstitial DC origin
  • A recent study reported immunphenotypes of nonneoplastic and neoplastic feline histiocytes and determined neoplastic cells of feline HS and FPH were variably positive for iDC/macrophage and LC markers which may indicate different phenotypes of these neoplasms
  • Immunphenotyping study results of feline nonneoplastic histiocytes: dermal interstitial dendritic cells (iDCs) and macrophages were CD204+/E-cadherin-, while epidermal Langerhans cells (LCs) were CD204-/E-cadherin+
    • Feline pulmonary Langerhans cell histiocytosis (PLCH)
      • Cutaneous histiocytoma does not occur in feline skin
        • Diffuse pulmonary infiltration by histiocytes, often leading to respiratory failure; can also have infiltration of pancreas, liver, kidney, lymph nodes
        • IHC positive for: vimentin, CD18, E-cadherin; expression of E-cadherin is reduced outside the lung
          • Ultrastructural findings: Intracytoplasmic Birbeck’s granules

Four-toed hedgehogs: A recent study reported immunohistochemical features of histiocytes, LCs, and histiocytic sarcomas in four-toed hedgehogs

• HLA-DR-, Iba-1- and E-cadherin-positive LCs were observed in the epidermis, while Iba-1- and CD204-positive histiocytes were detected in the lymph nodes and spleen of normal hedgehogs
• Localized HS developed in the skin and spleen; disseminated HS occurred in the intestine with distribution in multiple organs
• Tumor cells had variable features of histiocytic origin, but most tumor cells were immunopositive for Iba-1, CD204, and lysozyme

African pygmy hedgehog, sugar glider, Bengal tiger: Single case report

Piglet: Single case report of congenital cutaneous histiocytosis of non-Langerhans cell origin 

Puerto Rican crested toads: Occurred in 6/29 in a zoo-managed assurance population

 

Disease	Species	Cell of Origin	Immunophenotype
			Positive	Negative
Histiocytoma	Dog	Langerhans cell	CD1a, Cd11c/CD18, E-cadherin, Iba1	CD204
Cutaneous Langerhans cell histiocytosis	Dog	Langerhans cell	CD1a, Cd11c/CD18, E-cadherin, Iba1	CD204
Cutaneous histiocytosis	Dog	Activated interstitial DC	CD1a, CD4, CD11c/CD18, CD90 (Thy-1), Iba1	CD204
Systemic histiocytosis	Dog	Activated interstitial DC	CD1a, CD4, CD11c/CD18, CD90 (Thy-1), Iba1	CD204 (?)
Histiocytic sarcoma	Dog, cat	Interstitial DC	CD1a, CD11c/CD18, Iba1, CD204 (+/-)
Hemophagocytic histiocytic sarcoma	Dog, cat	Macrophage	CD1a (+/-), CD11d/CD18 (dog), CD204, Iba1
Feline progressive histiocytosis	Cat	Interstitial DC	CD1a, CD11c/CD18, CD5 (50%), CD204 (+/-), Iba1
Pulmonary Langerhans cell histiocytosis	Cat	Langerhans cell	CD1a, CD18, E-cadherin, CD204 (+/-), Iba1 (?)
Dendritic cell leukemia	Dog	Interstitial DC	CD1a, CD11c/CD18

*Modified from:

1. Moore PF. Canine and feline histiocytic disease. In: Meuten DJ, ed. Tumors in Domestic Animals. 5th ed. Ames, IA: Wiley Blackwell; 2017:322-336.

2. Moore PF. A review of histiocytic diseases of dogs and cats. Vet Pathol. 2014;51(1):167-184.

 

REFERENCES:  

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