How I investigate monocytosis.

Monocytosis is a common finding that is caused by a wide variety of neoplastic and non-neoplastic conditions. The adequate evaluation of monocytosis involves the integration of laboratory data, morphology, clinical findings, and the judicious use of ancillary studies. We review the literature on monocytosis, including the 2017 revised 4th edition of the World Health Organization classification of hematopoietic neoplasms. We present a review of monocytosis with practical guidelines on how to approach both routine and challenging cases.

Does morphology matter in 2017? An approach to morphologic clues in non-neoplastic blood and bone marrow disorders.

Numerous non-neoplastic and neoplastic conditions manifest with distinctive features in blood. Although automated complete blood count (CBC) data are essential, CBC information alone is insufficient for diagnosis. Consequently, morphologic review of blood smears is still relevant in the era of sophisticated automated analyzer systems. Pathologist interpretation of the peripheral blood smear, in conjunction with CBC and clinical information, can provide rapid diagnostic information and guide cost-effective targeted laboratory testing. Pathologist review of blood smears can be used to diagnose cases in which the clinical findings are misleading or nonspecific. Here, we discuss a selection of cases in which the pathologist examination of the blood smear can aid in rapid and accurate diagnosis and guide appropriate treatment. Exemplary non-neoplastic disorders with distinctive morphologic blood features of RBC, neutrophils, monocytes, and lymphocytes will be highlighted. The differential diagnostic considerations in blood smears with RBC destruction will be presented, expanding beyond microangiopathic hemolytic anemia. Lymphocyte morphologic assessment guides differential diagnosis including the identification of rare germline disorders. In each case presented, the integration of morphologic features guided additional testing with confirmation of the diagnosis. Peripheral blood smear review is timely and cost effective, even in an era of sophisticated automated laboratory testing.

Multidrug resistance-1 (MDR1) expression and functional dye/drug efflux is highly correlated with the t(8;21) chromosomal translocation in pediatric acute myeloid leukemia.

Resistance to chemotherapy is a major problem in acute myeloid leukemia (AML). An important resistance mechanism in adult AML is active drug efflux mediated by the multidrug resistance protein-1 (MDR1). To determine if MDR1 is important in childhood AML, we examined MDR1 expression and functional dye/drug efflux in 20 pediatric/adolescent AML patients; results were correlated with cytogenetics and clinical outcome. Using flow cytometry, MDR1 protein expression on the leukemic blasts was measured with the antibody MRK16, while efflux was measured by extrusion of the fluorescent dye DiO(C2)3 in the presence/absence of cyclosporin A (CsA). Six of 20 cases expressed MDR1. While all six MDR1+ cases were efflux+, three of 14 MDR1- cases also demonstrated efflux. Both MDR1 and efflux were strongly correlated with the t(8;21). All six MDR1 +/efflux+ cases and 2/3 MDR1 -/efflux+ cases had a t(8;21), while no MDR1-/efflux- cases had a t(8;21) (P < 0.0005). This correlation between MDR1, efflux, and the t(8;21) in pediatric AML was not found in 11 adult t(8;21) cases similarly studied. Although the clinical relevance of MDR1 in pediatric AML awaits larger studies, our results suggest a biologic subset of pediatric AML patients may benefit from regimens which include MDR1-reversing agents or non-MDR1 substrates.

Minimal residual disease in patients with hairy cell leukemia in complete remission treated with 2-chlorodeoxyadenosine or 2-deoxycoformycin and prediction of early relapse.

The purine nucleoside analogues 2-chlorodeoxyadenosine (2-CdA) and 2'-deoxycoformycin (2'-DCF) induce complete remission (CR) in the majority of patients with hairy cell leukemia. However, minimal residual disease (MRD) has been detected in bone marrow core biopsies using immunohistochemical techniques in patients achieving CR by conventional criteria. This study was designed to compare the prevalence of MRD with each agent in patients in CR by using conventional criteria and the relapse-free survival for patients with and without MRD. Bone marrow biopsies from 39 patients treated with a single cycle of 2-CdA and 27 patients treated with multiple cycles of 2'-DCF were studied. The monoclonal antibodies anti-CD20, DBA.44, and anti-CD45RO were used to evaluate the paraffin-embedded bone marrow core biopsies for MRD. Five of 39 patients (13%) treated with 2-CdA had MRD, as compared to 7 of 27 patients (26%) treated with 2'-DCF (two-tailed P = 0.21). Relapse has occurred in two of the five patients with MRD after 2-CdA treatment and in four of the seven patients with MRD after 2'-DCF treatment. In total, 6 of the 12 patients (50%) with MRD have relapsed, whereas 3 of 54 patients (6%) without MRD have relapsed, and 2 patients have died without evidence of relapse. The estimated 4-year relapse-free survival among patients with MRD is 55% (+/- 15%, SE), compared to 88% (+/- 5%, SE) among patients without MRD (two-tailed P = 0.0023). The prevalence of MRD detected in a subset of patients in CR after either 2-CdA or 2'-DCF treatment did not differ significantly. However, the presence of MRD is associated with an increased risk of relapse.

A retrospective study to assess the relative value of peripheral blood, bone marrow aspirate and biopsy morphology, immunohistochemical stains, and flow cytometric analysis in the diagnosis of chronic B cell lymphoproliferative neoplasms.

INTRODUCTION: The successful diagnosis of chronic B cell lymphoproliferative neoplasms (B-CLPN) requires the integration of multiple parameters, beginning with clinical information, CBC data, and morphology review. Immunophenotyping is essential and genetic testing may also be necessary. However, the relative value of each specimen or ancillary study in the diagnosis and classification has not been systematically established. We have performed a blinded retrospective review to assess what in our laboratory was the relative value of each specimen type and ancillary study in the diagnostic workup of B-CLPN. METHODS: A total of 185 cases of PB, BM, spleen and lymph nodes were analyzed for relative value of morphology, IHC, flow cytometry study in the diagnosis of B-CLPN. RESULTS: 'High yield' specimen was identified in most B-CLPN categories, which was highly predictive of the final WHO diagnosis. CONCLUSION: The goal of this retrospective study was to attempt to assess what was the relative value of morphology, immunophenotype, and molecular/cytogenetic study in various sites in the overall diagnostic process in our institution. We investigated the utility of the 'high yield' specimens in achieving the correct final diagnosis. In our study, some B-CLPNs notably splenic marginal zone lymphoma and hairy cell leukemia variant, required all studies for a 'best fit' type of diagnosis. In other cases, the morphology of a single specimen type was highly predictive of the final diagnosis, although confirmatory studies are recommended for definitive diagnosis.

The histopathology of cutaneous lesions of Kikuchi's disease (necrotizing lymphadenitis): a report of five cases.

Kikuchi's disease (KD) is an idiopathic, self-limited necrotizing lymphadenitis that can clinically and histologically mimic high-grade lymphoma, including Hodgkin's disease, or can be mistaken for the lymphadenitis of systemic lupus erythematosus (SLE). Involvement of extranodal sites is unusual but well documented, especially in Asia, where KD is more common than in North America or Europe. The successful distinction of KD from malignant lymphoma and SLE is imperative for the appropriate treatment of affected patients. We describe five patients with cutaneous involvement by KD, all of whom presented with fever, lymphadenopathy, and an eruption on the skin of the upper body, which in one case was clinically suspected to be due to SLE and in another, polymorphous light eruption. The patients ranged in age from 10 months to 42 years (median, 33 years) and included three females and two males. All five patients had negative serologic studies for collagen vascular disease. Each patient had a lymph node biopsy showing the typical necrotizing lymphadenitis of KD. Skin biopsies from all five patients shared a specific constellation of histologic features: vacuolar interface change with necrotic keratinocytes, a dense lymphohistiocytic superficial and deep perivascular and interstitial infiltrate, varying amounts of papillary dermal edema, and abundant karyorrhectic debris with a conspicuous absence of neutrophils and a paucity of plasma cells, paralleling the nodal histology in KD. CD68 immunohistochemistry on paraffin-embedded sections showed many histiocytes and plasmacytoid monocytes in all cases, whereas CD3, CD4, and CD8 showed highly variable staining among the cases. There was only rare staining with TIA-1 and CD30. We believe that the papular eruption of KD has recognizable histopathologic features and that a CD68 stain that marks many cells that initially seem to be lymphocytes can be performed to confirm the diagnosis.

Hantaviral biosafety issues in the autopsy room and laboratory: concerns and recommendations.

The need to perform autopsies on and examine laboratory specimens from patients with hantavirus pulmonary syndrome (HPS) has raised questions about biosafety. Human illness associated with hantaviruses is usually the result of exposure to infectious aerosols from saliva or excreta of wild rodents. It is unclear whether or nor certain autopsy and laboratory procedures can also generate similar potentially infectious aerosols. As the biosafety information developed for the HPS agent is limited and the consequences of infection are serious we recommend a cautious approach. Autopsy prosectors should use N-95 particulate respirators as a minimum standard. If aerosols will be generated they should use N-100 particulate respirators or powered air purifying respirators with high-efficiency particulate air (HEPA) filters. Centrifugation and cytocentrifugation of blood or body fluid samples should be performed in bio-contained systems and these specimen containers should be opened in a class II biological safety cabinet.

A B-cell "chameleon": striking clinical, morphological, and immunophenotypic diversity of a single low-grade B cell clone.

A patient with an 18-year history of low-grade B-cell lymphoproliferative disorders is presented. Although the precise classification of these B-cell disorders was problematic, the blood, bone marrow, spleen, lymph node, and gastrointestinal lesions evaluated were compatible morphologically with such apparently disparate diagnoses as hairy cell leukemia, marginal zone lymphoma, mantle cell lymphoma, and gastrointestinal multiple lymphomatous polyposis. Although each low-grade disease that developed over an 18-year interval was clinically, morphologically, and immunophenotypically distinct, genotyping showed their derivation from a single B cell clone. This case emphasizes that a single B-cell clone may give rise to several distinct low-grade B-cell lymphoproliferative disorders with diverse clinical and pathological features.

Hantavirus pulmonary syndrome in the United States: a pathological description of a disease caused by a new agent.

An outbreak of an acute respiratory disease in the southwestern United States has led to the recognition of a new hantaviral illness. This report describes a unique spectrum of antemortem and postmortem pathological findings seen in a case series of nine surviving patients and 13 who died. Clinical, laboratory, and autopsy findings were derived from a consecutive series of individuals confirmed to have hantavirus pulmonary syndrome. Laboratory studies included chemical, hematological, and bone marrow analyses as well as flow cytometric and immunohistochemical phenotyping. Autopsy tissues were examined by routine histological stains, immunohistochemical methods, and transmission electron microscopy. The lung is the primary target organ in this illness. Pulmonary abnormalities include pleural effusions, alveolar edema and fibrin, and an interstitial mononuclear cell infiltrate. Large immunoblast type cells are seen in the lungs, blood, bone marrow, lymph nodes, liver, and spleen. A tetrad of hematological findings includes left-shifted neutrophilic leukocytosis, thrombocytopenia, hemoconcentration in severe cases, and circulating immunoblasts. In contrast to previously described nephropathic hantaviral syndromes, hantavirus pulmonary syndrome is characterized by a unique constellation of pulmonary, hematological, and reticuloendothelial pathological findings. The pulmonary findings are distinguishable from fatal adult respiratory distress syndrome. The data suggest a capillary leak syndrome restricted to the pulmonary circulation. Likewise, the hematological picture is unique and may be valuable in the rapid identification of cases for further diagnostic studies.

Mitotic activity in benign parathyroid disease.

Tissue sections from 17 cases of parathyroid adenoma and ten cases of parathyroid hyperplasia were examined for mitotic activity. Mitoses were identified in 12 of the 17 cases of parathyroid adenoma and in eight of the ten cases of parathyroid hyperplasia. Clinical follow-up of all patients, even the four patients in whom numerous mitoses were present, showed no evidence of recurrent or aggressive disease. Mitotic activity alone is an unreliable indicator of aggressive potential in parathyroid disease.

Peripheral blood morphologic changes after high-dose antineoplastic chemotherapy and recombinant human granulocyte colony-stimulating factor administration.

The peripheral blood morphologic findings in 17 patients with cancer who had received high-dose cytotoxic chemotherapy followed by recombinant human-granulocyte colony-stimulating factor (rh-GCSF) were reviewed and compared with a control group of patients who received only high-dose chemotherapy. Both groups showed dysmyelopoiesis (abnormal granulation and nuclear lobulation) in the granulocytic series during the period of bone marrow recovery that followed the cytotoxic chemotherapy. Most of these morphologic abnormalities were more prominent in the rh-GCSF-treated group. Monocytic cells in both groups showed prominent vacuolation and immature nuclei. The percentages and absolute numbers of large granular lymphocytes were increased in the rh-GCSF group compared with the control group. No quantitative or qualitative abnormalities of eosinophilic or basophilic granulocytes were detected in either group. Both groups showed nonspecific red blood cell abnormalities, and large platelets were present in half of the control group smears. This report provides the first detailed peripheral blood morphologic description in patients treated with rh-GCSF and high-dose chemotherapy.

Bacterial infection stimulating granulocytic sarcoma of the small bowel.

A 57-year-old white man who had abdominal pain and distension, died after a short hospitalization for increasing ascites, anorexia, and deteriorating mental status. At autopsy, the principal gross finding was a dilated, hyperemic, thickened proximal jejunum that by light microscopy consisted of a transmural infiltrate of large mononuclear cells. Intense naphthol AS-D chloroacetate esterase (NASD) positivity was observed within most of the cells, suggesting granulocytic sarcoma. However, bacterial strains and electron-microscopic examination revealed that the massive jejunal infiltrate was composed of macrophages containing numerous phagocytosed bacteria. Although occasional cells had primary and secondary granules characteristic of myeloid precursors present within their cytoplasm, most cells lacked specific granules. Attempts to reproduce this markedly enhanced NASD result experimentally in peritoneal macrophages of mice were unsuccessful. This case shows that intense NASD cytoplasmic staining may occasionally occur macrophages that have phagocytosed large numbers of bacteria.

Prenatal diagnosis of transient myeloproliferative disorder via percutaneous umbilical blood sampling. Report of two cases in fetuses affected by Down's syndrome.

Since its initial description in 1982, percutaneous umbilical blood sampling has become useful in diagnosing, monitoring, and even treating a variety of fetal disorders. Recently two percutaneous umbilical blood samples were evaluated in which the white blood cell count was markedly elevated with many circulating blasts. Both samples exhibited the morphologic features of a transient myeloproliferative disorder, characteristically seen in neonates and infants with Down's syndrome. In both cases, antenatal clinical and ultrasound abnormalities also were suggestive of Down's syndrome, which was confirmed by cytogenetic studies. Although the peripheral blood abnormalities persisted at birth, both patients experienced spontaneous remission of the transient myeloproliferative disorder by 5 weeks of age. To our knowledge, these two cases of Down's syndrome represent the first reported examples of the intrauterine diagnosis of transient myeloproliferative disorders.

Colon ulceration in lethal cytomegalovirus infection.

Six renal transplant recipients with severe cytomegalovirus (CMV) infection developed colonic ulceration and lower gastrointestinal bleeding. All patients died between four and 84 days following onset of bleeding. Four patients required colon resection to control blood loss. In the remaining two cases, there was complete autopsy examination with thorough tissue sampling of the colon. In addition to routine light microscopic examination, all cases were studied with an immunoperoxidase technic for identification of CMV. Electron microscopic examination of the colon was performed on two cases. In this select group of patents, CMV plays an active role in damaging colonic mucosa, primarily as a result of CMC vasculitis. Clinical and pathologic features of our cases are compared to published reports of CMV infection of the colon.

Rapid presumptive diagnosis of hantavirus cardiopulmonary syndrome by peripheral blood smear review.

Hantavirus cardiopulmonary syndrome (HCPS) is a rare but frequently lethal acute zoonotic viral infection in rural North America. The rapidity of progression from febrile prodrome to cardiogenic shock and noncardiogenic pulmonary edema requiring intensive care creates high diagnostic urgency and a need for a rapid screening tool. In this retrospective cohort study, 2 pathologists scored blinded peripheral blood smears from 52 patients with HCPS and 128 seronegative patients referred for diagnosis of suspected hantavirus infection. During the prodromal phase, thrombocytopenia was the only consistent abnormality and could be used to indicate hantavirus serologic testing. After the onset of pulmonary edema detected radiographically, the presence of 4 of 5 findings (thrombocytopenia, myelocytosis, hemoconcentration, lack of significant toxic granulation in neutrophils, and more than 10% of lymphocytes with immunoblastic morphologic features) has a sensitivity for HCPS of 96% and a specificity of 99% and missed no patients with HCPS who required intensive care. While each abnormality is commonly seen, the combination of at least 4 of these CBC count data and peripheral blood smear findings can guide early treatment and patient transport decisions until rapid, specific, serologic testing becomes widely available.

Benign hematogone-rich lymphoid proliferations can be distinguished from B-lineage acute lymphoblastic leukemia by integration of morphology, immunophenotype, adhesion molecule expression, and architectural features.

Distinction of normal B-lymphoid proliferations including precursors known as hematogones from acute lymphoblastic leukemia (ALL) is critical for disease management. We present a multiparameter assessment of 27 bone marrow samples containing at least 25% hematogones (range, 25%-72%) by morphologic review. We used flow cytometry to evaluate B-cell differentiation antigen and adhesion molecule expression and immunohistochemistry on clot sections to evaluate architectural distribution. Flow cytometry revealed that intermediately differentiated cells (CD19+, CD10+) predominated, followed in frequency by CD20+, surface immunoglobulin-positive cells, with CD34+, terminal deoxynucleotidyl transferase (TdT)-positive cells as the smallest subset. Adhesion molecules (CD44, CD54) were expressed more heterogeneously compared with expression in acute lymphoblastic leukemia. Immunohistochemistry revealed that CD34+, TdT-positive cells were dispersed without significant clustering, while CD20+ cells exceeded CD34/TdT-positive cells in 24 of 25 cases. This multidisciplinary study demonstrates that hematogone-rich lymphoid proliferations exhibit a spectrum of B-lymphoid differentiation antigen expression with predominance of intermediate and mature B-lineage cells, heterogeneity of adhesion molecule expression, and nonclustered bone marrow architectural distribution.

Outbreak of Hantavirus pulmonary syndrome in the southwestern United States. Response of pathologists and other laboratorians.

During late spring and early summer of 1993, national and international media called worldwide attention to a cluster of deaths in the southwestern United States. These patients succumbed to a rapidly progressive severe respiratory distress syndrome. After notification of state and national health agencies in mid-May, a major effort was launched to determine the cause of this often fatal respiratory distress syndrome, to advise the public on safety measures, and to determine the method of spread of this "mystery illness." Within weeks of recognition of the early cases, the Centers for Disease Control and Prevention announced the probable agent, a Hantavirus. This report details the response of pathologists, medical technologists, and other laboratory scientists to this new viral epidemic, with emphasis on activities that occurred within New Mexico.

A comparative analysis of cytoplasmic mu (C mu) expression in acute lymphoblastic leukemia by molecular and immunologic techniques. Identification of leukemia cases expressing C mu mRNA transcripts in the absence of detectable C mu proteins.

Among acute lymphoblastic leukemias derived from the B-cell lineage, the subset of cases expressing cytoplasmic mu heavy chain proteins (C mu) in the absence of surface immunoglobulin has been designated pre-B-cell acute lymphoblastic leukemia. This group, traditionally identified using immunologic smear techniques, has been associated with a poor prognosis in some series. In a comparative study, 25 cases of B-lineage acute lymphoblastic leukemia were analyzed for C mu expression using molecular and immunologic techniques. RNA derived from cryopreserved blast cells was hybridized in both Northern and slot-blot analyses using a probe (pBZ311) containing four exons of the human immunoglobulin heavy chain mu constant region gene. Expression of C mu proteins was assessed simultaneously by slide immunofluorescence and flow cytometric techniques in all samples. These studies were correlated with immunoglobulin heavy and light chain gene rearrangements, cell-surface immunophenotype, cytogenetics, and other clinicopathologic features. C mu mRNA transcripts were detected in 14 of 25 cases, whereas C mu proteins were detected in only 9 of these cases using flow cytometric techniques. Only four of these nine cases were positive by slide immunofluorescence techniques. These studies imply that molecular and flow cytometric techniques may be a more sensitive means to assess C mu expression. The identification of five cases that expressed C mu mRNA transcripts in the absence of detectable C mu proteins also suggests that molecular techniques may be valuable in identifying a unique subgroup of pre-B-cell acute lymphoblastic leukemia cases that contain C mu mRNA transcripts, but lack C mu proteins.

Nonendemic adult T-cell leukemia/lymphoma in the United States: report of two cases and review of the literature.

Adult T-cell leukemia/lymphoma (ATLL) is a recently described distinct clinicopathologic entity characterized by a leukemic or lymphomatous proliferation of hyperlobulated peripheral T-cells, which is usually widespread at presentation and is associated with infection by a type C retrovirus. ATLL rarely is described outside of endemic regions, which include southwestern Japan, the Caribbean region, and the southeastern United States. The authors report the clinical, pathologic, and immunologic features of two cases of nonendemic ATLL that occurred in patients from the midwest United States. One patient was a 16-year-old white girl from rural Iowa, and the other was a 46-year-old white man from rural Minnesota. The features of 13 other probable nonendemic ATLL cases from the United States were compiled and reviewed. In the United States, nonendemic ATLL occurred in widespread geographic locations, affected mostly white people, and was characterized by an aggressive course with generalized adenopathy, blood and bone marrow involvement, and hepatosplenomegaly at presentation. Skin involvement was present in one-fourth of the patients. Hypercalcemia was rare. Although antibodies to type C retrovirus were detected in three of the five patients tested, the available data is not sufficient to establish a conclusive association between nonendemic ATLL and type C retrovirus infection.

The presence of CD34+ cell clusters predicts impending relapse in children with acute lymphoblastic leukemia receiving maintenance chemotherapy.

Early detection of relapse in children with acute lymphoblastic leukemia (ALL), as well as distinction of leukemic blasts from hematogones, can be difficult by morphologic examination alone. Using CD34 and terminal deoxynucleotidyl transferase (TdT) immunoperoxidase stains, we studied specimens from 25 children with ALL in morphologic remission to determine if we could identify children at risk of relapse. We studied morphologic remission bone marrow specimens from 9 patients who experienced relapse during the subsequent 6 months and 16 children who remained in complete remission, including 10 specimens with increased numbers of hematogones. Despite morphologic remission, clusters of more than 5 CD34+ and/or TdT-positive cells were identified before overt relapse in 6 of 9 cases of relapse, but were noted in only 1 of 10 specimens from children in continuous complete remission and none of 10 specimens with increased numbers of hematogones. Clusters of CD34+ or TdT-positive cells can identify individual patients at risk for imminent relapse. Hematogones may be differentiated from lymphoblasts by this method.