Fifth Edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues: Acute Lymphoblastic Leukemias, Mixed-Phenotype Acute Leukemias, Myeloid/Lymphoid Neoplasms With Eosinophilia, Dendritic/Histiocytic Neoplasms, and Genetic Tumor Syndromes

This manuscript represents a review of lymphoblastic leukemia/lymphoma (acute lymphoblastic leukemia/lymphoblastic lymphoma), acute leukemias of ambiguous lineage, mixed-phenotype acute leukemias, myeloid/lymphoid neoplasms with eosinophilia and defining gene rearrangements, histiocytic and dendritic neoplasms, and genetic tumor syndromes of the 5th edition of the World Health Organization Classification of Tumors of the Hematopoietic and Lymphoid Tissues. The diagnostic, clinicopathologic, cytogenetic, and molecular genetic features are discussed. The differences in comparison to the 4th revised edition of the World Health Organization classification of hematolymphoid neoplasms are highlighted.

mRNA sequencing analysis and growth inhibitory effects of palbociclib on cell lines from canine histiocytic proliferative disorders

Canine histiocytic proliferative disorders include aggressive and fatal diseases, such as histiocytic sarcoma (HS) and histiocytosis (SyH). The molecular mechanisms underlying cell proliferation need to be elucidated for the development of effective treatments. In the present study, mRNA expression levels were comprehensively analysed in cell lines derived from localized HS, disseminated HS, SyH and Langerhans cell histiocytosis (LCH) in dogs. Based on the results obtained, the growth inhibitory effects of palbociclib, a CDK4/6 inhibitor, were verified with the cell lines in vitro and in xenograft mouse model. Hierarchical clustering and principal component analysis plots of mRNA expression profiles divided the cell lines into three groups: a localized HS group, disseminated HS/SyH group, and LCH. The results of an ingenuity pathway analysis suggested that the MAPK signalling pathway was activated in the localized HS and LCH cell lines, and the PI3K signalling pathway in the disseminated and localized HS cell lines. In all cell lines, the expression of the tumour suppressor genes TP53, CDKN2A and CDKN1A was down-regulated, whereas that of Rb was preserved. In vitro assessments revealed the growth inhibitory effects of palbociclib in all cell lines examined. In a xenograft mouse model using a cell line from disseminated HS, palbociclib exerted significant growth inhibitory effects. These results suggest the potential of palbociclib as a therapeutic drug candidate for the treatment of malignant histiocytic proliferative disorders of the dog.

ALK-positive histiocytosis: a new clinicopathologic spectrum highlighting neurologic involvement and responses to ALK inhibition

ALK-positive histiocytosis is a rare subtype of histiocytic neoplasm first described in 2008 in 3 infants with multisystemic disease involving the liver and hematopoietic system. This entity has subsequently been documented in case reports and series to occupy a wider clinicopathologic spectrum with recurrent KIF5B-ALK fusions. The full clinicopathologic and molecular spectra of ALK-positive histiocytosis remain, however, poorly characterized. Here, we describe the largest study of ALK-positive histiocytosis to date, with detailed clinicopathologic data of 39 cases, including 37 cases with confirmed ALK rearrangements. The clinical spectrum comprised distinct clinical phenotypic groups: infants with multisystemic disease with liver and hematopoietic involvement, as originally described (Group 1A: 6/39), other patients with multisystemic disease (Group 1B: 10/39), and patients with single-system disease (Group 2: 23/39). Nineteen patients of the entire cohort (49%) had neurologic involvement (7 and 12 from Groups 1B and 2, respectively). Histology included classic xanthogranuloma features in almost one-third of cases, whereas the majority displayed a more densely cellular, monomorphic appearance without lipidized histiocytes but sometimes more spindled or epithelioid morphology. Neoplastic histiocytes were positive for macrophage markers and often conferred strong expression of phosphorylated extracellular signal-regulated kinase, confirming MAPK pathway activation. KIF5B-ALK fusions were detected in 27 patients, whereas CLTC-ALK, TPM3-ALK, TFG-ALK, EML4-ALK, and DCTN1-ALK fusions were identified in single cases. Robust and durable responses were observed in 11/11 patients treated with ALK inhibition, 10 with neurologic involvement. This study presents the existing clinicopathologic and molecular landscape of ALK-positive histiocytosis and provides guidance for the clinical management of this emerging histiocytic entity.

Descriptive Analysis of Histiocytic and Dendritic Cell Neoplasms: A Single-Institution Experience

PURPOSE

Histiocytic and dendritic cell neoplasms are rare hematologic tumors. This study aimed to describe the epidemiologic features of the entire spectrum of histiocytic and dendritic cell neoplasms, including clinicopathological variables and patient outcomes.

MATERIALS AND METHODS

We comprehensively reviewed 274 patients who were diagnosed with histiocytic and dendritic neoplasms at Severance Hospital, Seoul, South Korea between 1995 and 2018.

RESULTS

The most common neoplasm was Langerhans cell histiocytosis (LCH), followed by dermal xanthogranuloma. Among non-LCH sarcomas, histiocytic sarcoma (HS) showed a relatively high prevalence, followed by follicular dendritic cell sarcoma (FDCS). Disseminated juvenile xanthogranuloma (DJG), Erdheim-Chester disease (ECD), indeterminate dendritic cell tumor (IDCT), and interdigitating dendritic cell sarcoma (IDCS) rarely occurred. Generally, these tumors presented in childhood, although the non-LCH sarcoma (HS/FDCS/IDCS/IDCT) group of tumors and ECD occurred in late adulthood. Multiorgan involvement and advanced Ann-Arbor stage, as well as recurrence and death of disease, were not uncommon. The non-LCH sarcoma group had the worst overall survival, compared to the DJG, ECD, and LCH groups.

CONCLUSION

Our findings indicate that histiocytic and dendritic cell neoplasms exhibit heterogeneous epidemiologic characteristics and that some patients may have unfavorable outcomes, especially those with non-LCH sarcoma.

[Indeterminate cell histiocytosis - disappearance of skin infiltration following electron beam therapy and an application of 2-chlorodeoxyadenosine: case report]

Indeterminate cell histiocytosis is a rare disease belonging to the group of malignant histiocytic diseases. The disease predominantly affects the skin. The disease appeared in the described patient at the age of 80 years. Morphs began to develop on the skin and rapidly spread over the whole body including the face. Only the hands and feet were left uncovered. The patients skin samples were taken from 2 sites for histological examination. The resulting conclusion was indeterminate cell histiocytosis. The treatment we chose was analogous to the procedures for Langerhans cell histiocytosis. We chose PUVA phototherapy as the first-line treatment. This treatment is frequently efficient for skin forms of Langerhans cell histiocytosis. In the described case, however, PUVA phototherapy did not influence the disease activity at all. As the second-line treatment, we used low-energy electron beam irradiation in the total dose of 36.2 Gy. This treatment had a positive impact, morphs began to diminish and slowly disappear from the skin. But they have not disappeared completely, therefore we assessed the treatment effect of the radiotherapy itself as partial remission of the disease. Within the third-line treatment, we used 2-chlorodeoxyadenosine in a dose of 5 mg/m2/per day, administered via subcutaneous injection over 5 consecutive days in monthly intervals. There were three cycles of this treatment administered overall. The treatment with 2-chlorodeoxyadenosine was tolerated without any adverse effects. The patient aged 82 years was only administered 3 cycles of 2-chlorodeoxyadenosine. When after the 3rd cycle the skin was free from any pathological morphs and only some pigmentation spots remained, we finished the treatment. The skin expressions of indeterminate cell histiocytosis completely disappeared after electron beam irradiation and the following administration of 3 cycles of 2-chlorodeoxyadenosine. The remission was short, however, after 6 months the disease recurred and the treatment is planned to resume. We assume the disease regresses following administration of 2-chlorodeoxyadenosine, but more than 3 treatment cycles will probably be needed to reach a longer-term response.Key words: electron beam irradiation - indeterminate cell histiocytosis - 2-chlorodeoxyadenosine.

Feline Progressive Histiocytosis

Histiocytic proliferative diseases include reactive and neoplastic proliferations of dendritic cells (DC) or macrophages. Various forms of DC proliferations have been documented in humans and dogs; their etiology is largely unknown. With the exception of a few case reports, histiocytic proliferations have not been characterized in cats. This study summarizes clinical, morphologic, and immunophenotypic features of a feline progressive histiocytosis (FPH) in 30 cats. There was no breed or age predilection. Females were more often affected than males. Solitary or multiple nonpruritic firm papules, nodules, and plaques had a predilection for feet, legs, and face. Lesions consisted of poorly circumscribed epitheliotropic (13/30) and nonepitheliotropic (17/30) histiocytic infiltrates of the superficial and deep dermis, with variable extension into the subcutis. The histiocytic population was relatively monomorphous early in the clinical course. With disease progression, cellular pleomorphism was more frequently encountered. Histiocytes expressed CD1a, CD1c, CD18, and major histocompatibility complex class II molecules. This immunophenotype suggests a DC origin of these lesions. Coexpression of E-cadherin, a feature of cutaneous Langerhans cells, was only observed in 3 cats. FPH followed a progressive clinical course; the lesions, however, were limited to the skin for an extended period of time. Terminal involvement of internal organs was documented in 7 cases. Treatment with chemotherapeutics or immunosuppressive and immunomodulatory drugs was not successful. The etiology of FPH remains unknown. FPH is best considered an initially indolent cutaneous neoplasm, which is mostly slowly progressive and may spread beyond the skin in the terminal stage.

CD137 is expressed in follicular dendritic cell tumors and in classical Hodgkin and T-cell lymphomas: diagnostic and therapeutic implications

CD137 (also known as 4-1BB and TNFRSF9) is a member of the tumor necrosis factor receptor superfamily. Originally identified as a costimulatory molecule expressed by activated T cells and NK cells, CD137 is also expressed by follicular dendritic cells, monocytes, mast cells, granulocytes, and endothelial cells. Anti-CD137 immunotherapy has recently shown promise as a treatment for solid tumors and lymphoid malignancies in preclinical models. We defined the expression of CD137 protein in both normal and neoplastic hematolymphoid tissue. CD137 protein is expressed by follicular dendritic cells in the germinal center and scattered paracortical T cells, but not by normal germinal-center B cells, bone marrow progenitor cells, or maturing thymocytes. CD137 protein is expressed by a select group of hematolymphoid tumors, including classical Hodgkin lymphoma, T-cell and NK/T-cell lymphomas, and follicular dendritic cells neoplasms. CD137 is a novel diagnostic marker of these tumors and suggests a possible target for tumor-directed antibody therapy.

[Reactive and neoplastic histiocytic diseases in the dog]

There are different histiocytic diseases in dogs that are characterized by the proliferation of histiocytic cells (macrophages and myeloid dendritic cells). Histiocytic diseases can be devided into neoplastic (cutaneous histiocytoma complex, histiocytic sarcoma, dendritic cell leukaemia) and reactive forms (reactive histiocytosis, haemophagocytic syndrome). All subtypes of the cutaneous histiocytoma complex (cutaneous histiocytoma, metastatic histiocytoma and Langerhans' cell histiocytosis) are of Langerhans' cell origin. Histiocytoma, which is a solitary tumour of the skin in young dogs, shows spontaneous regression in most cases. Occasionally, metastasis to lymph nodes can be seen (metastatic histiocytoma). Only one dog with Langerhans' cell histiocytosis has been described and was euthanized. Histiocytic sarcoma, which arises from myeloid dendritic cells, can be classified as localised histiocytic sarcoma or disseminated histiocytic sarcoma. Another form of histiocytic sarcoma - haemophagocytic histiocytic sarcoma - is derived from macrophages. Histiocytic sarcoma displays a very aggressive clinical course and has a poor prognosis. Breed predispositions have been reported for the disseminated and haemophagocytic form of histiocytic sarcoma in Bernese mountain dogs, Rottweilers and varoiusretrievers. In contrast, reactive histiocytosis (cutaneous and systemic forms) develops by reactive proliferation of interstitial dendritic cells. In systemic histiocytosis, breed predilections are similar to histiocytic sarcoma. Haemophagocytic syndrome develops as a consequence of proliferation of activated macrophages in different tissues. Prognosis in general is moderate to poor and depends on the origin of the underlying disease process.

Hemosiderotic fibrohistiocytic lipomatous lesion: case report and review of the literature

CONTEXT

Lesions of the adipose tissue are the most common type of soft-tissue lesion among adults.

CASE REPORT

We describe the case of a 33-year-old female patient with a soft-tissue lesion in her left knee that was diagnosed as a hemosiderotic fibrohistiocytic lipomatous lesion. This type of lesion, which was described for the first time in 2000, preferentially affects the ankle region of middle-aged women with a history of previous local trauma. Lesion recurrence is common, caused by incomplete resection, although there have not yet been any reports of metastases. After a review of the literature, we describe the clinical, radiological, morphological and immunohistochemical characteristics, along with their main differential diagnoses.

Tumeurs fibrolipomateuses hémosidérotiques: une nouvelle entité à ne pas méconnaître

Fatty tissues lesions are the most frequent of both benign (lipoma) and malignant tumor (liposarcoma) of soft tissues in the adult. We here describe the case of female patient having a fatty tissue mass of the ankle corresponding to an hemosiderotic fibrohistiocytic lipomatous lesion (HFHLL). This very rare tumour of recent description is specific of the ankle/foot area of the middle age women. These lesions are always benign and frequently recur following incomplete resection. This tumor may have invasive local growth and metastases have not been described so far. We describe the anatomopathologist's key points of their diagnostic. We discuss the main differentials diagnosis and treatment.

Early development of histiocytic sarcomas in p53 knockout mice treated with N-bis(2-hydroxypropyl)nitrosamine

p53 knockout mice have been utilized for the functional analysis of p53 in carcinogenic processes and for the evaluation of the carcinogenic potential of chemicals. In this study, we established that p53 knockout mice have an elevated susceptibility to the induction of histiocytic sarcoma (HS) by N-bis(2-hydroxy-propyl)nitrosamine (BHP). p53 heterozygous (+/-) and wild-type (+/+) mice were treated with 20 or 200 ppm BHP in their drinking water for 15 weeks or with 20 ppm BHP for 40 weeks. An additional group of p53 nullizygous (-/-) mice were treated with 20 ppm BHP for 15 weeks. In a 15-week experiment, hepatic HSs were unexpectedly observed in BHP-treated p53 (-/-) mice (30.8%) but not in p53 (+/-) and (+/+) mice and untreated (-/-) mice, indicating that a complete loss of p53 dramatically accelerates the genesis of HS. In a 40-week experiment, HSs were significantly increased in female p53 (+/-) mice (37.5%) as compared with female (+/+) mice (5.0%). Additionally, PCR-SSCP and sequencing analysis revealed a high frequency of p53 gene mutations in HSs, demonstrating the involvement of p53 gene mutations in HS development. Our data add to the understanding of the carcinogenic susceptibility of p53 knockout mice, and may help to elucidate the pathogenesis of HS development.

Histiocytic sarcoma – A case with evenly distributed multinucleated giant cells

Histiocytic sarcoma is an uncommon neoplasm of mature histiocytes with a poor clinical outcome. We report a case of a true histiocytic sarcoma with prominent and evenly distributed multinucleated giant cells that mimics a giant cell tumor of soft tissue. The tumor was located between the appendix, right ovary, and the terminal ileum with severe adhesion. The liver and spleen were not enlarged. Grossly, the tumor appeared grayish white, solid, and soft. Microscopically, polygonal mononuclear tumor cells aggregated to form somewhat epithelioid nests, which occasionally showed coagulative necrosis. Prominent and evenly scattered giant cells were present in all sections. In addition, tumor cell infiltration was noted in regional lymph nodes. The tumor cells were positive for lysozyme, CD68, CD163, and negative for T- and B-cell lineage markers, follicular dendritic cell, megakaryocytic, epithelial, muscular, and melanocytic markers, CD1a and CD30. This case posed great difficulty in clinical and pathological diagnoses. Gross pictures, microscopic findings, and extensive immunostains are important for the differential diagnosis.

Primary central nervous system histiocytic sarcoma with relapse to mediastinum: a case report and review of the literature

Histiocytic sarcoma is a rare, malignant neoplasm of the lymphohematopoietic system that usually occurs in the skin, lymph node, and intestinal tract. Here we describe a unique case of primary central nervous system histiocytic sarcoma that initially showed an indolent clinical course following local resection and radiotherapy. However, relapse of disease within the mediastinum was noted 3 1/2 years later. Biopsies of the initial brain lesion and subsequent mediastinal recurrence each revealed an identical, diffuse proliferation of histiocytes with expression of CD45, CD68, and CD163 but not pan-cytokeratin, epithelial membrane antigen, CD3, CD15, CD20, CD30, CD43, CD79a, CD138, myeloperoxidase, ALK-1, PAX-5, CAM 5.2, S100, CD1a, or glial fibrillary acidic protein. In the literature, central nervous system histiocytic sarcoma portends a poor prognosis with median survival of 4.5 months. To our knowledge, this case represents the first case of "low-grade" primary central nervous system histiocytic sarcoma with relatively indolent clinical course. A thorough discussion of the differential diagnosis of histiocytic sarcoma and a review of primary central nervous system histiocytic sarcoma are also presented.

Carcinogenesis studies of benzophenone in rats and mice

Benzophenone, an aryl ketone, is used primarily as a photoinitiator and fragrance enhancer. Groups of 50 male and 50 female F344 rats and B6C3 F1 mice were fed diets containing 0, 312, 625, and 1250 ppm benzophenone for 105 weeks. Survival of males exposed to 1250 ppm benzophenone was significantly less than that of controls. There was a positive trend in the incidence of renal tubule adenoma in male rats; these neoplasms were accompanied by significantly increased incidences of renal tubule hyperplasia. Increased incidences of mononuclear cell leukemia were observed in male rats exposed to 312 or 625 ppm benzophenone and in female rats exposed to 625 ppm benzophenone. Liver lesions observed included significantly increased incidences of hepatocytic centrilobular hypertrophy in all exposed groups of rats. In mice, survival of all exposed groups was generally similar to that of the control groups. In male mice, there were significantly increased incidences of hepatocellular adenoma in the 625 and 1250 ppm groups. In female mice, the incidences of hepatocellular adenoma in the 625 and 1250 ppm groups were higher than expected after adjusting for the lower body weights in these groups. The incidences of kidney nephropathy in exposed groups of female mice, as well as the severity of nephropathy in exposed groups of males, were significantly increased. The incidences of metaplasia of the olfactory epithelium were significantly increased in 1250 ppm mice. Rare histiocytic sarcomas were observed in female rats and mice in the 625 and 1250 ppm groups. Under the conditions of these 2-year studies, there was some evidence of carcinogenic activity of benzophenone in male F344/N rats based on increased incidences of renal tubule adenoma. There was equivocal evidence of carcinogenic activity of benzophenone in female F344/N rats based on the marginal increased incidences of mononuclear cell leukemia and histiocytic sarcoma. There was some evidence of carcinogenic activity of benzophenone in male B6C3F(1) mice based on increased incidences of hepatocellular neoplasms, primarily adenoma. There was some evidence of carcinogenic activity of benzophenone in female B6C3F(1) mice based on increased incidences of histiocytic sarcoma; the incidences of hepatocellular adenoma in female B6C3F(1) mice may have been related to benzophenone exposure.

Canine hemophagocytic histiocytic sarcoma: a proliferative disorder of CD11d+ macrophages

Histiocytic disorders of dogs include histiocytoma, localized histiocytic sarcoma (HS), disseminated HS (malignant histocytosis), and the reactive histiocytoses: cutaneous and systemic. A common element to these diseases is proliferation of dendritic cells (DC) of either Langerhans cell (epithelial DC) or interstitial DC lineage. In this report, 17 dogs with hemophagocytic HS are described. Breeds affected included Bernese Mountain Dog (6), Golden Retriever (4), Rottweiler (3), Labrador Retriever (2), a mixed-breed dog, and a Schnauzer, which were from 2.5 to 13 years old. The dogs presented with Coombs negative responsive anemia in 16/17 dogs (94%), thrombocytopenia in 15/17 dogs (88%), hypoalbuminemia in 16/17 dogs (94%), and hypocholesterolemia in 11/16 dogs (69%). All dogs died or were euthanized. The clinical course ranged from 2 to 32 weeks (mean 7.1 weeks). Diffuse splenomegaly with ill-defined masses was consistently present. Microscopic lesions were prevalent in spleen, liver, lung, and bone marrow. Metastasis occurred by insidious intravascular invasion with minimal mass formation. Histiocytes were markedly erythrophagocytic and accompanied by foci of extramedullary hemopoiesis. Cytologically, the histiocytes varied from well differentiated to atypical, with atypia more prevalent in spleen than bone marrow. These tumors arose from splenic red pulp and bone marrow macrophages, which expressed major histocompatibility complex class II and the beta2 integrin, CD11d. They had low and/or inconsistent expression of CD1 and CD11c, which are dominantly expressed by canine nonhemophagocytic HS of DC origin. Canine histiocytic proliferative diseases now encompass proliferation of all members of the myeloid histiocytic lineage: Langerhans cells, interstitial DC, and macrophages.

Fibrohistiocytic skin tumors

The fibrohistiocytic tumors of the skin are a heterogeneous group of dermal/subcutaneous mesenchymal neoplasms which show fibroblastic, myofibroblastic and histiocytic (macrophage-like) differentiation, often one beside the other in the same tumor. "Fibrohistiocytic" means in this context the morphologic similarity of the cells with fibroblasts and histiocytes. The WHO classification of 2005 includes the following entities as fibrohistiocytic tumors of the skin: BENIGN: 1. Fibrous histiocytoma (FH)/(synonymous: Dermatofibroma. Variants of FH: 1a. cellular fibrous histiocytoma, 1b. atypical (pseudosarcomatous) fibrous histiocytoma, 1c. aneurysmatic fibrous histiocytoma, 1d. epithelioid fibrous histiocytoma; 2. dermatomyofibroma; 3. (juvenile) xanthogranuloma. INTERMEDIATE: 4. plexiform fibrohistiocytic tumor; 5. dermatofibrosarcoma protuberans; 6. atypical Fibroxanthoma. MALIGNANT: 7. malignant fibrous histiocytoma. All these entities are reviewed in this paper with particular attention devoted to differential diagnostic considerations.

The PTEN and INK4A/ARF tumor suppressors maintain myelolymphoid homeostasis and cooperate to constrain histiocytic sarcoma development in humans

Histiocytic sarcoma (HS) is a rare malignant proliferation of histiocytes of uncertain molecular pathogenesis. Here, genetic analysis of coincident loss of Pten and Ink4a/Arf tumor suppressors in the mouse revealed a neoplastic phenotype dominated by a premalignant expansion of biphenotypic myelolymphoid cells followed by the development of HS. Pten protein loss occurred only in the histiocytic portion of tumors, suggesting a stepwise genetic inactivation in the generation of HS. Similarly, human HS showed genetic or epigenetic inactivation of PTEN, p16(INK4A), and p14(ARF), supporting the relevance of this genetically engineered mouse model of HS. These genetic and translational observations establish a cooperative role of Pten and Ink4a/Arf in the development of HS and provide mechanistic insights into the pathogenesis of human HS.

Toxicology and carcinogenesis studies of benzophenone (CAS No. 119-61-9) in F344/N rats and B6C3F1 mice (feed studies)

Benzophenone is used as a photoinitiator, a fragrance enhancer, an ultraviolet curing agent, and occasionally as a flavor ingredient; it is also used in the manufacture of insecticides, agricultural chemicals, and hypnotics, antihistamines, and other pharmaceuticals; and it is used as an additive in plastics, coatings, and adhesive formulations. Benzophenone was nominated for study by the National Institute of Environmental Health Sciences based on its potential for occupational and consumer exposure and the lack of long-term toxicity data. Male and female F344/N rats and B6C3F1 mice were exposed to benzophenone (greater than 99% pure) in feed for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse bone marrow cells, and mouse peripheral blood erythrocytes. Results of 14-week toxicity studies in F344/N rats and B6C3F1 mice were reported earlier (NTP, 2000). 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 312, 625, or 1,250 ppm benzophenone (equivalent to average daily doses of approximately 15, 30, and 60 mg benzophenone/kg body weight to males and 15, 30, and 65 mg/kg to females) for 105 weeks. Survival of 1,250 ppm males was significantly less than that of controls. Mean body weights of 1,250 ppm males were markedly less than those of the controls during year 2 of the study, and weights of exposed females were consistently less than controls throughout the study. Feed consumption by 1,250 ppm males was less than that by the controls after week 70; feed consumption by 1,250 ppm females was generally less than that by the controls throughout the study. There was a positive trend in the incidences of renal tubule adenoma in males, and the incidences in 625 and 1,250 ppm males exceeded the historical control range for all routes; these neoplasms were accompanied by significantly increased incidences of renal tubule hyperplasia. Due to these findings, additional kidney sections were evaluated; results indicated additional renal tubule adenomas in all groups of males and renal tubule hyperplasia in all groups of males and females. The incidences of pelvic transitional epithelium hyperplasia and the severity of nephropathy were significantly increased in all exposed groups of male rats. Increased incidences of mononuclear cell leukemia in all exposed groups of females exceeded the historical control range from feed studies, and the incidence in 625 ppm females was significantly greater than that in the controls. Male rats exposed to 312 or 625 ppm had significantly increased incidences of mononuclear cell leukemia. One 625 ppm female and two 1,250 ppm females had histiocytic sarcomas, and the incidence in the 1,250 ppm group exceeded the range in the historical controls. Liver lesions included significantly increased incidences of hepatocytic centrilobular hypertrophy in all exposed groups of males and females, cystic degeneration in 625 and 1,250 ppm males, and bile duct hyperplasia in all exposed groups of females. Incidences of mammary gland fibroadenoma in females exposed to 625 or 1,250 ppm were lower than expected after adjusting for body weight. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 312, 625, or 1,250 ppm benzophenone (equivalent to average daily doses of approximately 40, 80, and 160 mg/kg body weight to males and 35, 70, and 150 mg/kg to females) for 105 weeks. Survival of all exposed groups of mice was generally similar to that of the control groups. Mean body weights of exposed females were less than vehicle controls. Feed consumption by exposed males and females was similar to that by the controls. In male mice, there were significantly increased incidences of hepatocellular adenoma in the 625 and 1,250 ppm groups, and these incidences exceeded the historical control range. All hepatocellular neoplasms combined occurred with a positive trend. In female mice, the incidences of hepatocellular adenoma in the 625 and 1,250 ppm groups were higher than expected after adjusting for the lower body weights in these groups. Incidences of centrilobular hepatocyte hypertrophy were significantly increased in all exposed groups of males and females. All exposed groups of male mice had significant increases in the incidences of multinucleated hepatocytes and chronic active inflammation. The incidences of cystic degeneration of hepatocytes in 625 and 1,250 ppm males were significantly increased. The incidence of histiocytic sarcoma in 625 ppm females was significantly increased and exceeded the historical control range. The incidences of kidney nephropathy and mineralization in exposed groups of females and the severity of nephropathy in exposed groups of males were significantly increased. The incidences of metaplasia of the olfactory epithelium were significantly increased in 1,250 ppm males and females. The incidences of hyperplasia of lymphoid follicles in the spleen were significantly increased in all exposed groups of males and in 312 and 625 ppm females.

GENETIC TOXICOLOGY

Benzophenone was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, with or without hamster or rat liver activation enzymes. No significant increases in the frequencies of micronucleated polychromatic erythrocytes were seen in bone marrow samples from male mice administered benzophenone three times by intraperitoneal injection. In addition, no increases in micronucleated normochromatic erythrocytes were noted in peripheral blood of male or female mice administered benzophenone for 14 weeks in dosed feed.

CONCLUSIONS

Under the conditions of these 2-year studies, there was some evidence of carcinogenic activity of benzophenone in male F344/N rats based on increased incidences of renal tubule adenoma; mononuclear cell leukemia in male F344/N rats may have been related to benzophenone exposure. There was equivocal evidence of carcinogenic activity of benzophenone in female F344/N rats based on the marginally increased incidences of mononuclear cell leukemia and histiocytic sarcoma. There was some evidence of carcinogenic activity of benzophenone in male B6C3F1 mice based on increased incidences of hepatocellular neoplasms, primarily adenoma. There was some evidence of carcinogenic activity of benzophenone in female B6C3F1 mice based on increased incidences of histiocytic sarcoma; the incidences of hepatocellular adenoma in female B6C3F1 mice may have been related to benzophenone exposure. Administration of benzophenone in feed resulted in increased incidences and/or severities of nonneoplastic lesions in the kidney and liver of male and female rats and in the liver, kidney, nose, and spleen of male and female mice. Decreased incidences of mammary gland fibroadenoma in female rats were related to benzophenone exposure.

CY15, a malignant histiocytic tumor that is phenotypically similar to immature dendritic cells

The origin and pathogenesis of histiocytic malignancies and the biology of the tumor cells are poorly understood. We have isolated a murine histiocytic tumor cell line (CY15) from a BALB/c IFNgamma(-/-) mouse and characterized it in terms of phenotype and function. The morphology, as judged by electron microscopy, and the surface marker phenotype suggests that CY15 cells are similar to immature dendritic cells (CD11c (low), MHC II (low), CD11b(+), B7.1(+), B7.2(+), and CD40(+)). The cells form tumors in BALB/c mice and metastasize to spleen, liver, lung, kidney, and to a lesser extend to lymph nodes and bone marrow, as judged by the growth of green fluorescent protein transfected tumor cells in mice. CY15 cells are capable of actively taking up antigen (FITC-ovalbumin) and can stimulate T lymphocytes in an allogenic mixed lymphocyte reaction but less effectively than their normal counterparts (immature dendritic cells). They respond to interleukin 4 (IL-4) with up-regulation of CD11c. If stimulated with IFNgamma the cells up-regulate MHC II, CD40 B7.1, and B7.2. Lipopolysaccharide induces the cells to up-regulate B7.1 and B7.2 and to secrete tumor necrosis factor alpha and IL-12. Based on these data, CY15 is a dendritic cell-like tumor cell line and may serve as a transplantable tumor model for histiocytosis in humans.

Histiocytic sarcoma: a study of five cases including the histiocyte marker CD163

Histiocytic sarcoma (HS) is a rare but controversial hematopoietic neoplasm. In the past, malignancies have been misclassified as histiocytic tumors due to overlapping histologic features and inadequate phenotypic data. CD163, a recently characterized hemoglobin scavenger receptor, appears to be a 'specific' marker of histiocytic lineage and a promising diagnostic tool for evaluating histiocytic neoplasms. Five cases of HS were studied to further elucidate the clinicopathologic features of these rare tumors and to demonstrate the diagnostic utility of CD163. Criteria for diagnosis included histologic and immunohistochemical evidence of histiocytic differentiation, CD45 positivity, and exclusion of lymphoid, epithelial, melanocytic and dendritic cell phenotype. Sites of disease included the colon (two cases), palate, inguinal lymph node, and testis. The clinical course was aggressive in 4/5 patients (survival=2-15 months). One patient with localized disease of the palate, survived 17 years after diagnosis. All patients with poor survival had tumors > or =3.5 cm. Histologically, all cases showed diffuse architecture with large, discohesive polygonal cells. Spindling of cells was focally noted. Hemophagocytosis was identified in 3/5 cases. A prominent inflammatory background was present in 4/5 tumors. All cases were immunoreactive for CD45, CD163, CD68, and lysozyme. S-100 was focally positive in 4/5 cases. Antibodies for melanocytic, epithelial, lymphoid, and dendritic cell markers were negative. Molecular studies showed monoclonal IgH gene rearrangements in three cases. Our findings suggest that HS is an uncommon neoplasm frequently extranodal in presentation and aggressive in behavior, with rare exceptions. Stage of disease and possibly tumor size are significant prognostic indicators. Molecular studies remain controversial in the diagnosis. The morphologic and phenotypic features are relatively uniform; however, the diagnosis requires exclusion of more common neoplasms by extensive immunophenotypic studies. CD163 appears to be a specific histiocytic marker and is important in establishing the diagnosis of HS.

Malignant Melanoma with Osteoclast-Like Giant Cells: An Unusual Host Response

Melanomas with unusual histologic features are very rarely reported in the literature and demonstrate the diversity of melanocytic expression. Three cases of malignant melanoma with osteoclast-like giant cells are reported. Two cases showed undifferentiated malignant cells without melanin pigment and one showed spindled cell morphology. Immunohistochemistry showed that the osteoclast- like giant cells expressed CD68, but not melanocytic markers (HMB45, Melan-A, and S100). Ultrastructural analysis further supports that these cells are reactive histiocytes rather than transformed malignant cells. This suggests they represent an unusual host response, similar to those rarely observed in other neoplasms. Awareness of this entity is important to avoid misdiagnosis of melanoma as a histiocytic tumor. Since only few cases have been reported, greater recognition and documentation may help to evaluate the prognosis of such cases with unusual morphology.

Histiocytic proliferations in childhood

Histiocytic disorders occur with increased frequency in children and young adults. The wide spectrum of neoplastic and nonneoplastic diseases characterized by histiocytic proliferation was reflected in the cases submitted to the 2003 Society for Hematopathology and the European Association for Haematopathology Workshop. This review focuses on the entities represented at the workshop. It includes an overview of the classification and immunophenotype of the histiocytic disorders. The clinical and pathologic features of each entity are illustrated with representative cases submitted to the workshop, with an emphasis on recent biologic and genetic insights. In addition, a brief review of the pathologic features of the lysosomal storage disorders is included, with an emphasis on findings relevant to the practicing hematopathologist, exemplified with cases presented at the workshop.

Histiocytic sarcoma associated with Hodgkin's disease

Histiocytic sarcoma is a rare malignant neoplasm. It is well-known the association of Langerhans' cell histiocytosis with Hodgkin's disease but only few cases of histiocytic sarcoma associated with Hodgkin's disease was reported. We present the case of 20-years-old female patient with Hodgkin's disease with a sternal tumor mass which was diagnosed as histiocytic sarcoma. The diagnostic was established immunohistochemically, using a large battery of antibodies (S-100, CD 68, CD 34, CD 15, CD 30, Vim, NFAP) and by electron microscopy which revealed the lack of the Birbeck granules in the malignant proliferated histiocytes.

Histiocytic sarcoma with interdigitating dendritic cell differentiation

The authors describe a rare tumor with overlapping features of true histiocytic sarcoma and interdigitating dendritic cell sarcoma occurring in infancy. A 3-month-old boy presented with hepatosplenomegaly and abdominal distention. He presented a diagnostic challenge at initial presentation despite extensive investigations. On follow-up at age 16 months he had progressive splenomegaly, thrombocytopenia, and worsening coagulopathy. A diagnosis of histiocytic sarcoma with interdigitating dendritic cell differentiation was established after an open biopsy of liver and spleen. A repeat liver biopsy coupled with splenic biopsy is recommended in young children with unexplained hepatosplenomegaly and thrombocytopenia.

[Histiocytic sarcoma from phagocyting histiocytes]

Histiocytic sarcoma consisting of phagocyting histiocytes is a rare variant of histiocytic sarcoma. It is hard to detect because of its similarity with large cell lymphomas, in particular with anaplastic large cell lymphoma. Histological and immunohistochemical findings are presented. Differential diagnosis with tumours of hematopoietic and non-hematopoietic nature is described.

Cutaneous true histiocytic malignancy: true histiocytic lymphoma

True histiocytic malignancies (THM) are controversial disorders that are being re-evaluated with modern cellular and molecular biology techniques. True histiocytic lymphoma (THL) is a low-incidence, poor-prognosis THM. It mainly affects the skin, gastrointestinal tract, and bone tissues. Occasionally, skin lesions are the presenting clinical features. A patient with initially cutaneous THL is described. This and other reported cases confirm that THM are a nosologic entity by themselves.

Establishment of a new canine cell line (CCT) originated from a cutaneous malignant histiocytosis

A new canine cell line, named CCT, was established from the cutaneous malignant histiocytosis in a 4-year-old male Borzoi. CCT proliferated with loose adherence and doubling time was approximately 30 hr. When co-cultured with latex beads, CCT phagocytized beads vigorously. Lysozyme and vimentin were positive by immunostaining, and non-specific esterase and acid phosphatase were positive by cytochemical staining. These features indicated the cells had a histiocytic nature. Furthermore, by subcutaneous injection to nude mice CCT could successfully form tumors with the morphological and immunohistochemical features similar to the original tumor.

Update on panniculitis

There is considerable confusion regarding the pathogenesis, nosology and treatment of panniculitis. This paper examines newer concepts in five types of panniculitis: i.e., histiocytic cytophagic panniculitis, erythema induratum, lipodermatosclerosis, pancreatic panniculitis and alpha-1-antitrypsin deficiency panniculitis. Recent developments in etiology, pathogenesis, molecular techniques, and therapy are discussed.

t(2;5) associated with a histiocytic-monocytic neoplasm

We describe a patient with a neoplasm derived from the histiocytic-monocytic lineage associated with t(2;5) detected by FISH. The patient presented with bone marrow involvement, no organomegaly and subsequently developed a leukaemic picture. The clinical course was aggressive and the patient died four months from diagnosis. Cell morphology, immunophenotype (CD30-, EMA-, Lisozyme+, cy CD68+ and CD45+) and DNA analysis showing germ-line configuration of the Ig/TCR chain genes ruled out the diagnosis of anaplastic large cell lymphoma (ALCL). This unusual case ilustrates that t(2;5) is not exclusive for ALCL but may be found in a few cases of rare neoplasms derived from the histiocytic-monocytic cells.

[Sarcoma consisting of dendritic reticular cells]

Sarcoma consisting of dendritic reticular cells is one of the histiocytic sarcoma variants. In the case reported sarcoma affected axillary lymph nodes in a 20-year-old male. The tumor was surgically removed but recurred 2 years after radiation and polychemotherapy. The recurrent tumor was also surgically removed. Histology of the primary and recurrent tumors was similar. The tumors were studied electron-microscopically and immunohistochemically.

Antimacrophage monoclonal antibody D11 in the diagnosis of tumors of histiocytic origin

OBJECTIVE

To investigate the possible application of the human antimacrophagal antibody D11 (MAb D11) to the diagnosis of tumors of histiocytic origin.

STUDY DESIGN

Biopsy and surgical materials from 181 patients with nonepithelial tumors and tumorlike lesions were used in the study. The reactivity of MAb D11 with tumor cells was assayed as the percentage of positively reacted cells in cryostat sections and on smears of tissues determined by the immunoperoxidase method.

RESULTS

According to the reaction, all tumors could be divided into three groups: group 1, 39 cases, including all malignant fibrous histiocytomas (MFH) (24 cases); all tumors were D11 antigen positive; group 2, 130 cases, tumors with the same nosologic forms revealed positive, as well as negative, reactions with MAb D11; and group 3, 12 cases, all tumors exhibited a negative reaction with MAb D11.

CONCLUSION

Although MAb D11 gave a positive reaction with all tumors in the histiocyte series, its reactivity with some tumors of other histogeneses limits the application of MAb D11 for differential diagnosis of MFH. Nevertheless, MAb D11 may be used for the exclusion of tumors from the MFH group in the case of a negative reaction. The results support the view that MFH is derived from cells of the mononuclear phagocyte system.

Histiocyte disorders

Histiocyte disorders are characterised by tissue infiltration with cells of monocyte/macrophage lineage, with two disorders, Langerhans' cell histiocytosis (LCH) and haemophagocytic lymphohistiocytosis (HLH) accounting for the overwhelming majority of cases in childhood and, apart from monocyte variants of acute myeloid leukaemia, histiocytic malignancy is very rare. Although both LCH and HLH are considered reactive disorders, the prognosis of these conditions differs greatly, LCH is usually self limiting, with a mortality of 10%, but HLH is usually fatal, with a mortality of over 80% in the absence of bone marrow transplantation. Increased levels of cytokines have been demonstrated in these disorders, and may be responsible for many of the clinical features: it is unclear whether histiocytes themselves, or other immune cells, particularly T lymphocytes, are the abnormal cell population. Due to the rarity of histiocyte disorders, collaborative studies are essential to improve understanding and advance treatment.

"Pseudoneoplastic" leprosy. Leprosy revisited

A 70-year-old Italian man with a history of squamous cell carcinoma of the lung presented with a nodular skin eruption. He had traveled extensively in India and Sri Lanka. The nodules were well demarcated and measured up to 3.5 cm in diameter. Histologically, there was a proliferation of spindled and polygonal cells with focal and relatively inconspicuous cytoplasmic vacuolation. A macrophage-monocyte lineage for the cells was confirmed by paraffin section immunohistochemistry, using the monoclonal antibodies anti-CD45, MAC-387, KP-1, UCHL-1, MT-1, L26, and MB2. Infiltrating borders, extension of the lesion into the subcutis, and involvement of small dermal nerves and eccrine glands initially suggested the possibility of a "histiocytic" neoplasm of indeterminate biological potential. However, air-dried and Giemsa-stained material from a fine-needle aspirate of one cutaneous nodule showed needle-shaped intracellular "negative images," and acid-fast stains revealed a large number of intracytoplasmic bacilli in virtually all of the vacuolated lesional cells. Furthermore, a second skin nodule that was excised 3 weeks after initial presentation showed the typical morphology of lepromatous leprosy. The clinicopathologic features of this case demonstrated several similarities with those of so-called "histoid" leprosy. Unusual morphologic variants of leprosy need to be considered in the interpretation of unusual "histiocytic" infiltrates in order to avoid a mistaken diagnosis of neoplasia, regardless of the geographic locale in which the patient is evaluated.

Histiocytic sarcomas and monoblastic leukemias. A clinical, histologic, and immunophenotypical study

Eight histiocytic sarcomas, identified by examination of more than 2000 malignant lymphomas, are described. For comparison, tumor infiltrates from five monoblastic leukemias were also analyzed. The histiocytic sarcomas were all high-grade malignancies consisting of markedly pleomorphic large cells with many mitotic figures. At presentation, six of the patients had systemic symptoms (fever, fatigue, loss of weight), skin infiltrates, and lymphadenopathy. Despite aggressive chemotherapy, clinical remissions were short, and six patients died of disease .5-48 months (mean, 6.5 months) after diagnosis. The remaining two patients are alive and in partial or complete remission 7 and 12 months after diagnosis. Immunotypic examination showed that all the histiocytic sarcomas were positive for macrophage-related antigens and negative for antigens on B cells, T cells, myeloid cells, epithelial cells, and melanocytes. T-cell receptor and immunoglobulin genes were studied in three cases and were present in a germline configuration. One of the histiocytic sarcomas resembled Langerhans' cells in phenotype and morphology; it was classified as a Langerhans' cell sarcoma. The remaining histiocytic sarcomas did not express accessory cell-associated antigens, but more closely resembled "ordinary" tissue macrophages; they were positive for lysozyme and/or CD68, followed in frequency by CD11c, CD4, CD11b, CDw32, peanut agglutinin receptor, and CD13. Similar features were seen in the monoblastic leukemias. These conditions could only be distinguished from histiocytic sarcoma by clinical and morphologic, rather than immunophenotypic, criteria. Expression of oncoprotein p53 was studied in nine cases and was positive in six of six histiocytic sarcomas and one of three monoblastic leukemias. Rare malignancies show features consistent with the derivation from macrophages. Two entities may be distinguished: those that resemble antigen-presenting accessory cells and those that more closely resemble ordinary tissue macrophages. Recognition of these tumors is important clinically and requires assessment of clinical, morphologic, and immunophenotypic features, supplemented by analysis of T-cell receptor and immunoglobulin genes. Whether (or how) p53 gene mutations are implicated in their pathogenesis will be an important topic for future investigation.

Intravascular histiocytosis

The majority of cases of intravascular lymphomatosis are B-cell lymphomas with only the occasional case being of T-cell type. We report a case of intravascular lymphomatosis in which the proliferating cells were of histiocytic type; the tumour has recurred following treatment.

Spontaneous histiocytic sarcoma with possible origin from the bone marrow and lymph node in Donryu and F-344 rats

Ninety-five male and 96 female Donryu rats reared up to 120 wk of age and 244 male and 243 female F-344 rats used as untreated controls in 5 carcinogenicity studies were examined histopathologically to clarify the primary site of histiocytic sarcoma. Histiocytic sarcoma in Donryu rats was observed in 5 of 95 (5.3%) males and 4 of 96 (4.2%) females. In F-344 rats, 4 of 244 (1.6%) males and 3 of 243 (1.2%) females had the neoplasms. Histologically, sarcomas consisting of large pleomorphic histiocytic cells were seen in the bone marrow, liver, lymph node, spleen, and lung. Among 16 sarcomas observed, 15 had neoplastic lesions in the bone marrow, and 1 F-344 rat had the lesions only in the lymph nodes. Eleven (6 F-344 rats and 5 Donryu rats) of the 15 cases had the lesions in the liver, and 4 Donryu rats had no lesions in the liver but lesions in the lymph node and/or spleen, except for 1 case where the sarcoma occurred only in the bone marrow. Among the 11 cases with the lesions both in the liver and bone marrow, neoplastic lesions were found also in the lymph node, spleen, and/or lung, but the severity of neoplastic proliferation of these organs was not so marked as that in the bone marrow except for 2 cases. Although histiocytic sarcomas in rats are considered to originate from the liver, peritoneum, or subcutis, the present results strongly suggest that some histiocytic sarcomas in Donryu and F-344 rats may also originate from the bone marrow and lymph nodes.