Hematopathology Flashcards
This is the appearance of normal bone marrow at medium magnification. Note the presence of megakaryocytes, erythroid islands, and granulocytic precursors. This marrow is taken from the posterior iliac crest in a middle aged person, so it is about 50% cellular, with steatocytes admixed with the marrow elements.
This is the appearance of normal bone marrow smear at high magnification. Note the presence of an eosinophilic myelocyte, a basophilic myelocyte, and a plasma cell.
Normochromasia
The red blood cells here are normal, happy RBC’s. They have a zone of central pallor about 1/3 the size of the RBC. The RBC’s demonstrate minimal variation in size (anisocytosis) and shape (poikilocytosis). A few small fuzzy blue platelets are seen. In the center of the field are a band neutrophil on the left and a segmented neutrophil on the right.
A normal mature lymphocyte with a single large nucleus is seen on the left, compared to a segmented neutrophil on the right with multiple nuclear lobes connected by thin chromatin bridges, along with cytoplasmic granules. An RBC is seen to be about 2/3 the size of a normal lymphocyte.
Though granulocytes survive a matter of hours, lymphocytes survive weeks, or even months. They may enter and exit the circulation to reside in places such as lymphoid tissues.
The RBC’s in the background appear normal. The important finding here is the presence of many PMN’s. An elevated WBC count with mainly neutrophils suggests inflammation or infection. This neutrophilia increases the total WBC count. This neutrophilia consists of segmented neutrophils and band neutrophils, but not eosinophils or basophils.
An elevated WBC count with segmented neutrophils as well as more immature band neutrophils and even metamyelocytes suggests more severe inflammation or infection driving accelerated release of myeloid cells from the bone marrow. This is known as a ‘left shift’. A very high WBC count (>50,000) with pronounced left shift that is not a leukemia is known as a “leukemoid reaction”. This reaction can be distinguished from malignant WBC’s by the presence of large amounts of leukocyte alkaline phosphatase (LAP) in the normal neutrophils.
WBC count & differential
The RBC’s here have stacked together in long chains. This is known as “rouleaux formation” and it happens with increased serum proteins, particularly fibrinogen and globulins. Such long chains of RBC’s sediment more readily. This is the mechanism for the sedimentation rate, which increases non-specifically with inflammation and increased “acute phase” serum proteins [CRP, SAA, fibrinogen, haptoglobin; activated by IL1 and IL6]
Anisocytosis
Variation in RBC size
Poikilocytosis
a condition where 10% or more of the red blood cells are abnormally shaped due to other medical conditions
Anemia in disease
Inflammatory conditions release cytokines such as interleukins 1 and 6 (IL1, IL6) that stimulate hepatic production of hepcidin,
During conditions in which the hepcidin level is abnormally high, such as inflammation, serum iron falls due to iron trapping within macrophages and liver cells and decreased gut iron absorption. This typically leads to anemia due to an inadequate amount of serum iron being available for developing red blood cells. When the hepcidin level is abnormally low such as in hemochromatosis, iron overload occurs due to increased ferroportin mediated iron efflux from storage and increased gut iron absorption.
Hepcidin induction by inflammation is presumed to have evolved to sequester iron from pathogenic microorganisms.
The result is decreased total serum iron, but iron binding capacity is reduced as well, resulting in a somewhat decreased saturation, but increased ferritin. Serum soluble transferrin receptors will be unaffected by chronic disease states. Anemia of chronic disease is addressed by treating the underlying condition.
Transferrin
glycoproteins found in vertebrates which bind to and consequently mediate the transport of Iron (Fe) through blood plasma. They are produced in the liver and contain binding sites for two Fe3+ ions. Human transferrin is encoded by the TF gene and produced as a 76 kDa glycoprotein.
Transferrin glycoproteins bind iron tightly, but reversibly
Hematopoietic elements in this bone marrow biopsy are markedly reduced. This is a case of aplastic anemia. Of course, besides, RBC’s the platelets and granulocytes will often be diminished. Sometimes a drug or toxin is the cause and sometimes infection. When no known cause can be found, it is termed idiopathic aplastic anemia.
In contrast to aplastic anemia, leukemia results in a highly cellular marrow. The marrow between the pink bone trabeculae seen here is nearly 100% cellular, and it consists of leukemic cells of acute lymphocytic leukemia (ALL) that have virtually replaced or suppressed normal hematopoiesis. Thus, though the marrow is quite cellular, there can be peripheral cytopenias. This explains the complications of infection (lack of normal leukocytes), hemorrhage (lack of platelets), and anemia (lack of red blood cells) that often appear with leukemia.
The WBC’s seen here are lymphocytes, but they are blasts–very immature cells with scant cytoplasm and large nuclei that contain nucleoli. Such abnormal lymphocytes are indicative of acute lymphoblastic leukemia (ALL). ALL is more common in children than adults. Many cases of ALL in children respond well to treatment, and many are curable.
These mature lymphocytes are increased markedly in number. They are indicative of chronic lymphocytic leukemia, a disease most often seen in older adults. This disease responds poorly to treatment, but it is indolent.
CLL is defined by more than 5000/microliter B lymphocytes in peripheral blood marking with CD23 and CD5. Over half of patients are diagnosed at an early, asymptomatic stage, without lymphadenopathy, splenomegaly, cytopenias, or autoimmune phenomena. With counts >10,000/microliter, progression and severity of CLL become more likely.
Though CLL is a B cell proliferation, marking with CD19 and CD20, it is characterized by the presence of a T cell marker, CD5, as shown by flow cytometry here. This is a systemic disease, and organ involement outside of marrow, such as spleen and liver, is known as small lymphocytic lymphoma (SLL).
Here are very large, immature myeloblasts with many nucleoli. A distincitve feature of these blasts is a linear red “Auer rod” composed of crystallized granules. These findings are typical for acute myelogenous leukemia (AML) that is most prevalent in young adults.
Leukemias typically fill up the marrow with abnormal cells, displacing normal hematopoiesis. The marrow here is essentially 100% cellular, but composed almost exclusively of leukemic cells. Normal hematopoiesis is reduced via replacement (a “myelophthisic” process) or by suppressed stem cell division. Thus, leukemic patients are prone to anemia, thrombocytopenia, and granulocytopenia and all of the complications that ensue, particularly complications of bleeding and infection.
At high power, the bone marrow of a patient with acute myelogenous leukemia is seen here. There is one lone megakaryocyte at the right center.
There are numerous granulocytic forms seen here, including immature myeloid cells and bands. This condition is one of the myeloproliferative states and is known as chronic myelogenous leukemia (CML) that is most prevalent in middle-aged adults. A useful test to help distinguish this disease is the leukocyte alkaline phosphatase (LAP) score, which should be low with CML and high with a leukemoid reaction.
Here is another view of a peripheral blood smear in a patient with CML. Often, the numbers of basophils and eosinophils, as well as bands and more immature myeloid cells (metamyelocytes and myelocytes) are increased. Unlike AML, there are not many blasts with CML.
Here is the normal appearance of a benign reactive lymph node. Lymphatics that drain tissues peripheral to the node enter the subcapsular sinus and lymph percolates around and into lymphoid follicles of variable size and having a surrounding mantle zone that is surrounding a pale germinal center in which the immune responses are often generated with a predominance of B cells. Sinusoids extend to the center of the node.
This is a more pronounced reactive change in a lymph node, with a larger follicle and germinal center containing ‘tingible body’ macrophages. These large macrophages are involved in phagocytosis of antigenic material passed from follicular dendritic cells to be processed into peptides. In general, lymph nodes in a benign reactive process are more likely to enlarge quickly and become tender.
Here is a lymph node involved by lymphoma, a malignant process characterized by the proliferation of neoplastic lymphoid cells. The capsule of the node has been invaded and the lymphomatous cells extend into the surrounding adipose tissue. Note that the follicles are numerous and irregularly sized. This is a follicular center cell malignant lymphoma (also described as small cleaved cell type, follicular, or as malignant lymphoma, poorly differentiated lymphocytic type, nodular).
This pattern of malignant lymphoma is diffuse and no lymphoid follicles are identified in this lymph node. Note that the normal architecture of the lymph node is obliterated. The lymph node is replaced by an infiltrate of small (mature-appearing) neoplastic lymphocytes, and the infiltrate extends through the capsule of the lymph node and into the surrounding fat. These cells will mark as B lymphocytes. The diagnosis is: small lymphocytic lymphoma (SLL). This is the tissue equivalent of chronic lymphocytic leukemia (CLL), and both often occur together (CLL/SLL). Though both are indolent, they are widespread and difficult to treat.
Many non-Hodgkin’s lymphomas seen in adults are large cell lymphomas such as the one here at medium power, but they can be associated with immunosuppressed states (such as AIDS), and are typically of B cell origin. The cells are large, with prominent nucleoli and abundant cytoplasm. This disease tends to be localized (low stage), but with more rapid enlargement, and a greater propensity to be extranodal than the low grade lymphomas.
The malignant lymphocytes here are very large with a moderately abundant cytoplasm, and the nuclei are round to ovoid with prominent nucleoli and occasional mitoses. The diagnosis is diffuse large B cell lymphoma (also known as immunoblastic lymphoma). The major differential diagnosis in this case would be a metastatic carcinoma. The presence of monoclonal immunoglobulin as demonstrated by immunohistochemical technique would help to confirm this lesion as a malignant lymphoma. Demonstration of CD19 and 20 antigens would classify it as B cell in origin.
A bone marrow biopsy can reveal malignant lymphoma. Here are peritrabecular infiltrates of small blue cells which is the lymphomatous infiltrate.
The skull demonstrates the characteristic rounded “punched out” lesions of multiple myeloma. The plasma cell proliferation results in bone lysis to produce these lytic lesions. Such lesions can produce bone pain and lead to hypercalcemia.
The destruction of bone is primarily due to increased osteoclast activity from cytokine activation. The myeloma cells can produce tumor necrosis factor (TNF), macrophage inflammatory protein (MIP) to induce greater nuclear factor kappa B ligand (RANKL), and downregulate osteoprotegerin (OPG) production, as diagrammed below.
At medium power, the plasma cells of multiple myeloma here are very similar to normal plasma cells, but they may also be poorly differentiated. Usually, the plasma cells are differentiated enough to retain the function of immunoglobulin production. Thus, myelomas can be detected by an immunoglobulin “spike” on protein electrophoresis, or the presence of Bence-Jones proteins (light chains) in the urine. Immunoelectrophroesis characterizes the type of monoclonal immunoglobulin being produced.
Here is a smear of bone marrow aspirate from a patient with multiple myeloma. Note that there are numerous plasma cells with eccentric nuclei and a perinuclear halo of clearer cytoplasm.
Hodgkin Lymphoma classification
Hodgkin Lymphoma Features and Staging
Hodgkin lymphoma (HL), formerly called Hodgkin disease (HD) may respond well to therapy. Thus, it is important to determine the stage of the disease and the histologic type of HD in order to provide the most appropriate therapy. The first four types listed in the table below are “classical HL” and have Reed-Sternberg cells that immunohistochemically are positive for CD15 and CD30 but negative for CD45.
Nodular lymphocyte-predominant HL has RS cells that are CD20 positive but CD15 and CD30 negative, like B cells.
This is Hodgkin’s disease, nodular sclerosis type. Note the bands of pink collagenous tissue dividing the field in this lymph node.
At medium power, nodular sclerosing Hodgkin’s disease has prominent bands of fibrosis. Staging of Hodgkin’s disease is important to try and determine therapy and the prognosis. Staging is often done by radiographic means, with CT scans used to determine where lymphadenopathy is located, ultrasonography to determine size and lesions of liver and spleen, and chest radiograph. Histologic diagnosis is typically made from biopsy of an involved lymph node. A bone marrow biopsy is typically performed as well. Staging laparotomy is less commonly used nowadays because the radiographic procedures are excellent.
In this lymph node, there are numerous scattered large cells with a surrounding prominent clear space surrounding the nucleus, an artefact of formalin fixation. These are the lacunar cells characteristic for the nodular sclerosis type of Hodgkin lymphoma.
Note the large cells with large, pale nuclei containing large purple nucleoli at the arrowheads. These are Reed-Sternberg cells that are indicative of Hodgkin’s disease. Most of the cellular content of foci of Hodgkin lymphoma consists of reactive lymphoid cells. There are four main subtypes of classic Hodgkin lymphoma with CD15+ Reed-Sternberg cells and variants: lymphocyte rich, nodular sclerosis, mixed cellularity, and lymphocyte depletion. The lymphocyte predominance subtype with CD15- Reed-Sternberg variant cells acts more like a low-grade B-cell lymphoma.
At low power, the abnormal plasma cells of multiple myeloma fill the marrow.
The lymph node in cat scratch disease shows one or more foci of “stellate micro-abscesses” characterized by foci of necrosis bounded by palisaded histiocytes. Non-necrotizing granulomas or foci of naked necrosis may also be seen. Although the histologic findings are nonspecific they are so characteristic that staining for bacteria with Warthin-Starry or other appropriate staining should be undertaken.
Marginal zone lymphoma is a low grade B-cell lymphoma that can arise in lymph nodes, spleen, or viscera (MALT lymphoma). Peripheral blood involvement is uncommon but can be seen in splenic or nodal forms. This smear shows several lymphocytes that are slightly larger than normal small lymphocytes in blood and show slightly eccentric nuclei (long arrows). A large granular lymphocyte is also shown (arrowhead). Flow cytometric analysis of blood showed a monoclonal B-cell population without any co-expression of CD5, CD10, or CD23. Further evaluation identified primary splenic marginal zone lymphoma.
