A Problem of Classification: 2 Cases of Epstein-Barr Virus + Primary Cutaneous Plasmacytoma Arising in Immunocompetent Elderly Patients

ABSTRACT

Primary extramedullary plasmacytoma is rare monoclonal proliferation of plasma cells, which arise in various nonosseous anatomic locations without detectable underlying systemic disease. Historically, cutaneous infiltrates rich in mature neoplastic plasma cells have fallen into one of the following categories, plasmacytoma, lymphoplasmacytic lymphoma, and marginal zone lymphoma, which included immunocytoma. Since 2005, each of these was subsumed under the marginal zone lymphoma umbrella, largely on the basis of acknowledged diagnostic difficulties in some of these cases. We describe 2 cases in which the cutaneous infiltrates consisted of a pure population of light chain-restricted mature plasma cells in the absence of any other evidence for a marginal zone proliferation, or evidence of extracutaneous involvement, including a paraprotein. We propose that primary cutaneous plasmacytoma is the accurate diagnosis and is consistent with wider nomenclature. The unusual observation of widespread Epstein-Barr virus expression in both tumors is also discussed.

[Extramedullary plasmacytoma of the head and neck]

The aim of this review was to present plasma cell neoplasms, their development, common features and classification. Extramedullary plasmacytoma (EMP) is a most often plasma cell neoplasm in the head and neck. 80-90% EMP cases concern to head and neck: 40% nasal cavity and paranasal sinuses, about 20% nasopharynx, 18% oropharynx. Tumour symptoms are similar like in other neoplasm. It is very important to remember about plasma cell neoplasm during differential diagnosis because of relatively common occurrence. Extramedullary plasmacytoma is radiosensitive neoplasm with good prognosis therefore radiation therapy is the method of choice.

Clinico-pathological aspects of canine cutaneous and mucocutaneous plasmacytomas

In this study the clinico-pathological aspects of cutaneous and mucocutaneous plasmacytomas were investigated in 63 dogs (one dog with two tumours). The tumours were most commonly observed in the skin of the trunk and legs. Yorkshire Terrier (n = 8) was the most commonly affected breed and males were affected more commonly than females (36 versus 23, respectively). Plasmacytomas were histologically classified into mature, hyaline, cleaved, asynchronous, monomorphous blastic and polymorphous blastic cell types. Monomorphous blastic cell type was the most frequent type (n = 21), followed by cleaved (n = 19) and asynchronous (n = 11) cell types. Secondary amyloid depositions were observed in eight cases. Immunohistochemical staining showed monoclonal lambda light chain positivity in all cases. In the immunohistochemical staining for cyclin D1, which is a prognostic marker in human plasma cell tumours, moderate numbers of positive tumour cells were observed in only one case of (muco)cutaneous plasmacytoma. All other cases were negative or contained few positive tumour cells. On the other hand, high numbers of tumorous plasma cells reacted positively with cyclin D1 in three out of six cases of canine multiple myelomas. Prognosis of the (muco)cutaneous plasmacytomas was good, except in one dog which developed a lymphoma afterwards. No significant correlations were observed between the cell type and the location of the tumour, presence of amyloid or prognosis.

Lymphoid neoplasms in HIV-positive individuals in India

The HIV epidemic in the Asian subcontinent has a significant impact on India. Patients with AIDS have an increased risk of developing non-Hodgkin lymphoma (NHL). In this study, we have investigated the pattern of distribution of lymphoid neoplasms and also studied the Epstein-Barr virus (EBV)-association and p53 expression in 35 HIV-positive patients from India. The biopsy samples were studied for histology and for expression of CD20, CD3, CD15, CD30, light chains, CD138, bcl-6, epithelial membrane antigen, EBV-latent membrane protein-1, and p53 protein. In situ hybridization was performed with digoxigenin-labeled anti-sense EBV-encoded nuclear RNA-1 (EBER-1) probe. Polymerase chain reaction (PCR) was performed on DNA extracted from paraffin sections for EBV-subtype analysis. The 35 cases included 7 cases of Hodgkin disease (HD), 4 cases of plasmacytoma (PL), and 24 cases of NHL. Among the cases of NHL, 3 were Burkitt lymphoma (BL), 4 were diffuse large B-cell lymphoma (DLBL) of centroblastic type (CBL), 10 were DLBL of immunoblastic type (IBL), 4 were high-grade B-cell lymphoma (unspecified) and the rest were other subtypes. EBV-association was noted in all cases of HD, 2 of 3 BL, and 3 of 10 IBL. PCR analysis of the EBNA-3C gene revealed amplimers corresponding to type A. A p53 protein overexpression was noted in 6 of 10 IBLs, 1 of 3 BLs, 2 of 3 CBLs, and 5 of 7 cases of HD. This is the first reported study of lymphoid malignancies in HIV-positive individuals from India.

[Locally recurring extramedullary plasmacytoma of the upper aerodigestive tract]

BACKGROUND

Extramedullary plasmacytomas (EMP) are plasma cell tumors in which by definition the primary tumor is extramedullary. Most of them are found in the upper aerodigestive tract.

PATIENTS

In this study we describe 3 patients with EMP. The first case is a locally recurrent EMP with recurrent involvement of cervical lymph nodes. The first manifestation of EMP was 31 years ago. Hence, this is one of the longest clinical courses of recurrent EMP ever described in the literature. Case 2 is a locally aggressive recurrent EMP. Case 3 is a localized solitary EMP that could be successfully treated by surgery alone.

RESULTS AND CONCLUSIONS

Different classifications of EMP described in the literature are discussed. If these classifications are applied to our cases neither the tumor stage nor the histological picture allow definite conclusions about the prognoses to be drawn. Metastases in regional lymph nodes do not necessarily mean a worse prognosis. Overall, compared to MM with a ten year survival rate of 18% the prognosis is more favorable in EMP with a ten year survival rate of 50%. After a generalized plasma cell neoplasia has been excluded EMP in the head and neck should be treated like a locally aggressive and potentially metastatic tumor. From our experiences we recommend a primary surgical therapy followed by radiation therapy if necessary.

Prognostic value of histopathological grading in canine extramedullary plasmacytomas

The canine extramedullary plasmacytoma (cEMP) has recently been the subject of numerous investigations, indicating that the histomorphologic diagnosis is often difficult because of the variety of morphologic features. Therefore, the objective of this study was to establish a subclassification scheme for cEMPs and to evaluate correlations between the types and malignancy. Retrospectively, 117 cEMPs, all immunohistochemically characterized by a monoclonal immunoglobulin light-chain expression, were collected and assigned to morphologic types. These types were compared using data from a follow-up study on metastasis and tumor recurrence, then compared by proliferation rate, determined by immunohistochemical detection of the antigen Ki-67. Histopathologic typing revealed five different types of cEMPs, ranging from the mature type with typical plasma cells to the polymorphous-blastic type. Between these two forms, three additional types were established: hyaline, cleaved, and asynchronous. Most of the cEMPs were of the cleaved and asynchronous types. In all cEMPs, mononuclear and multinuclear giant cells were present to varying degrees. Although the results of cell proliferation and the follow-up study indicated less benign behavior by the polymorphous-blastic type, the proliferation rate revealed no statistically significant differences among the cEMP types. The clinical data therefore confirmed previous findings that the risk of tumor recurrence and metastasis in general can be classed as low. The established cEMP typing system is probably a very helpful diagnostic tool, although the types cannot be used for a tumor grading system.

Extramedullary plasmacytoma. A form of marginal zone cell lymphoma?

Extramedullary plasmacytoma (EMP), solitary plasmacytoma of bone, and multiple myeloma are related neoplasms, but EMP is clearly a distinct entity. Moreover, there are histologic and clinical similarities between EMP and marginal zone B-cell lymphomas (MZLs) displaying extensive plasma cell differentiation, suggesting a possible histogenetic relationship. The histologic and clinical features of 5 EMPs with extensive plasma cell differentiation were histologically reviewed for features of MZL. The previously diagnosed MZLs, mucosa-associated lymphoid tissue (MALT) type, of 2 patients also were reviewed. All patients were women aged 48 to 79 years. The EMPs originated in the parotid gland, lymph nodes, dura, or small bowel. The initial tumors diagnosed as MALT-type MZL were located in the lung and small bowel. All patients were treated with resection, with or without irradiation therapy. One patient also received systemic chemotherapy. All patients are alive with no evidence of disease. All tumors contained large numbers of plasma cells, constituting between 55% and 90% of the lymphoid cells. Centrocyte-like cells and monocytoid B cells each represented 0% to 25% of the infiltrate. Lymphoepithelial lesions were observed in all of the tumors in sites where epithelium was present. Reactive follicles were found in all of the tumors. EMPs may represent MZLs that have undergone an extensive degree of plasmacytic differentiation.

Primary B-cell lymphomas of the skin

Primary B-cell lymphomas of the skin are not as rare as is generally believed. They are defined as malignant B-cell proliferations presenting with cutaneous involvement alone and no evidence of extracutaneous manifestations over a period of at least six months when complete staging has been performed. The major subtypes are follicle center-cell lymphoma of the head and trunk, immunocytoma and large B-cell lymphoma of the leg (EORTC classification 1996). Also of interest is the recently recognized marginal-zone B-cell lymphoma. Primary B-cell lymphomas of the skin differ significantly from nodal lymphomas. Awareness of their special clinical behavior should prevent unnecessarily aggressive treatment.

Plasma cell dyscrasias: classification, clinical and laboratory characteristics, and differential diagnosis

Plasma cell dyscrasias form a heterogeneous group of diseases characterized by the expansion of the number of monoclonal bone marrow plasma cells that produce monoclonal immunoglobulins. Sensitive electrophoretic methods have shown that the incidence of these diseases is as high as 5% in adult individuals. Thus, the majority of cases should be considered to be a normal phenomenon. A few transform into neoplastic diseases, plasma cells becoming responsible for lytic bone lesions, the hallmark of MM. The distinction of benign and malignant forms is frequently difficult at presentation. We can easily recognize solitary myeloma, overt myeloma and plasma cell leukaemia, which require immediate chemotherapy. Therapy could be safely withheld in all the remaining forms, which require only follow-up. Thus, we suggest that plasma cell dyscrasias should be classified simply into two main groups according to the need of immediate chemotherapy. The appearance of new bone lesions and the increase of the M-component level remain the only two criteria that define malignant transformation. Several clinical and laboratory prognostic parameters indicate the risk of transformation, and hence how close the follow-up of the patient should be. Parameters related to the expansion of the plasma cell clone (percentage of bone marrow plasma cells, M-component level, lytic bone lesions and beta 2-microglobulin) are not always very low and very high in the benign and malignant forms, respectively, and frequently overlap in patients with intermediate plasma cell expansions. On the contrary, all parameters related to the intrinsic malignancy of the plasma cells (plasma cell LI, Karyotypic abnormalities and molecular alterations) have, by definition, to be normal in the benign forms. MRI is a new tool that may, early on, reveal lytic bone lesions undetectable by conventional radiography.

Leukemias, myeloma, and other lymphoreticular neoplasms

BACKGROUND

The purpose of this study was to assess the occurrence of various morphologic types of leukemia and myeloma within patient demographic groups and to correlate findings with data-reporting periods and other variables, such as 5-year relative survival.

METHODS

Data from 31,850 cases of multiple subgroups of acute and chronic leukemia, 12,237 cases of myeloma, and 321 cases of "other" lymphoreticular neoplasms were collected by the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) program. The data were examined by age, sex, race, age-specific and age-adjusted incidence rate, and patient 5-year relative survival during three reporting periods: 1973-1977, 1978-1982, and 1983-1987.

RESULTS

The age-adjusted incidence rate for all categories of leukemia combined has been constant, but there has been an increase in the relative frequency (percentage) of acute lymphoid leukemia (ALL) in the general population and a rising incidence rate of myeloid leukemia in the black population. The increase of ALL is offset by a decline of acute myeloid leukemias (AMLs) and acute leukemia, not otherwise specified. The age-adjusted rate of ALL in whites, 1.5 per 100,000 per year, is twice that of blacks, 0.8. The rates for each of the major categories of leukemia are considerably higher in males than in females. Five-year survival rates changed very little for leukemias over the 15 years of the study except for ALL, in which there was a marked improvement between the first (1973-1977) (39.1%) and second (1978-1982) (51.3%) reporting period. The SEER data confirm that multiple myeloma is predominantly a disease of late adulthood and occurs more frequently in blacks and males. The incidence rate of multiple myeloma has not changed during the 15 years surveyed. The 5-year relative survival rate has remained nearly constant for multiple myeloma. There is a marked difference in 5-year relative survival rates for patients with plasmacytoma of bone marrow (45.7%), multiple myeloma (25.9%), and plasma cell leukemia (13.0%).

CONCLUSIONS

Shifts in the relative frequencies of leukemia types may have been affected by changes in classification criteria, changes in the use of histologic terms over time, and the expanded use of immunophenotyping and other technology to characterize acute leukemias. Incidence rates and 5-year relative survival rates for myeloma have remained stable.

Extramedullary plasmacytoma of the thyroid, associated with follicular colonization and stromal deposition of polytypic immunoglobulins and major histocompatibility antigens. Possible categorization in MALT lymphoma

A 78-year-old woman complaining of a neck mass underwent right hemithyroidectomy. The 7 x 6 cm thyroid tumor consisted predominantly of mildly atypical, epithelial membrane antigen-positive plasma cells and scattered lymphoid follicles. Features of follicular colonization (plasma cell infiltration into germinal centers) were noted. Numerous CD45RO-positive reactive T cells and a smaller number of CD20-positive blast-like B cells were also distributed among the plasma cell infiltrate. IgG, kappa-type monoclonality with J-chain reactivity was identified in the plasma cells, including those in the lymphoid follicles. The association of pre-existing lymphocytic thyroiditis was confirmed histologically in the non-tumorous thyroid tissue. The tumor exhibited deposition of reticulin fiber-rich, amorphous eosinophilic substances, provoking pronounced foreign body reactions. The deposit, polytypically immunoreactive for immunoglobulin gamma-, mu-, kappa- and lambda-chains, beta 2-microglobulin and HLA-DR, was scarcely reactive upon amyloid staining, and consisted ultrastructurally of electron-dense, non-fibrillar material and entrapped collagen fibers. Multiple myeloma was ruled out by laboratory, histologic and clinical examinations. The possible categorization of this extramedullary plasmacytoma of the thyroid within low-grade B cell lymphoma of the mucosa-associated lymphoid tissue (MALT) is discussed.

Successful in vitro graft-versus-tumor effect against an Ia-bearing tumor using cyclosporine-induced syngeneic graft-versus-host disease in the rat

Lethally irradiated LouM rats reconstituted with syngeneic bone marrow and then treated with cyclosporine (CsA) for 40 consecutive days following transplant developed a graft-v-host disease (GVHD)-like syndrome after CsA cessation. This model of GVHD was used to define and characterize a graft-v-tumor (GVT) effect against a syngeneic plasmacytoma CRL1662 cell line which expresses class II major histocompatibility (MHC) antigen (Ia). Nylon wool-nonadherent spleen cells from animals who developed syngeneic GVHD were capable of significant lysis against chromium-labeled tumor target cells in a four-hour chromium released cell mediated lympholysis assay; maximum lysis occurred five days following cessation of CsA when clinical signs first appeared. Cytolytic activity declined to baseline as GVHD symptoms resolved. Fractionation of splenocytes into lymphocyte subsets demonstrated that cytolytic lymphocytes (CTLs) of the OX8 phenotype (non-helper T) were capable of significant lysis against tumor target cells. Lysis of tumor cells was blocked by preincubation with monoclonal antibodies (MoAb) specific for the rat anti-class II MHC antigen but not with MoAb against class I. Incubation of tumor cells with gamma-interferon increased expression of tumor class II MHC antigens and significantly increased their susceptibility to lysis by nylon wool-nonadherent splenocytes from animals with syngeneic GVHD. These studies have demonstrated an in vitro GVT of syngeneic GVHD against an Ia-bearing tumor; the effector cell is a CTL of the OX8 phenotype specific for the class II MHC antigen.

[A comparison of staging classifications of plasmacytoma]

In 152 patients treated with cytostatic agents for multiple myeloma the prognostic value of seven staging systems was evaluated: Carbone et al. Acute Leukemia Group B, Southeastern Cancer Study Group, Durie and Salmon, Alexanian, Merlini et al., British Medical Research Council. The staging systems of the ALGB and SECSG, both dividing patients into "good risk"- and "poor risk"-groups gave significantly different survival curves. Nevertheless, the differences were rather small. In the systems of Carbone et al., Merlini et al., Alexanian, and Durie and Salmon some of the differences in the survival curves were statistically significant while others were not. Our data best fitted into the British Medical Research Council staging system, the survival curves of all three stages showing significant differences with median survival time dropping from 83 months in stage A to 52 months in stage B and 26 months in stage C. Nevertheless, none of those systems was clearly superior to single risk factors especially creatinine and hemoglobin.

B-cell neoplasms of the lymphocytic, lymphoplasmacytoid, and plasma cell types: immunohistologic analysis and clinical correlation

The relation between chronic lymphocytic leukemia (CLL, lymphocytic lymphoma (SL), plasmacytoid lymphocytic lymphoma (LP), plasmacytoma (PL), and multiple myeloma (MM) was investigated with cryostat sections stained with antibodies to immunoglobulin heavy and light chains and the B-cell differentiation antigens B1, B2, Ia, T1, and CALLA. Neoplasms were subclassified according to plasmacytoid features, leukemia (CLL) site of involvement (nodal or extranodal), serum monoclonal immunoglobulin, or clinical evidence of MM. The results defined two groups of lymphocytic lymphomas without plasmacytoid features (16 cases). Ten of these lymphomas were associated with CLL. Nine involved lymph nodes, all expressed IgM, five expressed IgD, nine were B2-positive, eight were T1-positive, and all were B1- and Ia-positive. Six of the lymphomas were not associated with CLL. Five of these tumors were extranodal, all were T1- B1+ B2- Ia+, five expressed IgM without IgD, and one contained IgG. These differences in clinical and immunologic phenotypes suggest that CLL and SL without CLL may be related to different stages of B-cell differentiation. T1 appeared to be a marker for CLL, since all T1-positive neoplasms were leukemic. Lymphomas with plasmacytoid features (ten cases) were more often extranodal, and none was leukemic. The immunologic phenotypes were heterogeneous: all of these lymphomas were T1-negative, most were IgM+ IgD-, three were B2-positive, and all were Ia-positive. The plasma cells in five lymphomas with marked plasmacytoid features were B1-negative; they were Ia-positive in four and Ia-negative in one. These data suggest that LP is a heterogeneous group, reflecting B cells at diverse stages of differentiation. Ten plasmacytomas, nine of which were associated with MM, differed from LP in showing heavy chain class switching; all were T1- B1- B2-, and all but one were Ia-negative. These results are consistent with the existence of two pathways or stages of B-cell differentiation: one that generates IgM-producing plasma cells, as seen in the primary immune response or in response to pokeweed mitogen, and one that generates IgG- or IgA-positive plasma cells, as seen in the late primary or secondary immune response. Plasmacytoid lymphocytic lymphoma reflects the first, while PL/MM reflects the second pathway. B1 appears to be lost before Ia in terminal plasma cell differentiation.

Histomorphology and cytomorphology of cutaneous B-cell lymphomas

This article summarizes the conceptual and morphologic background for the diagnosis of cutaneous B-cell lymphomas (CBCL). The architectural pattern of the infiltrate and cytomorphology can indicate the B-cell nature of a skin lymphoma. Virtually all types of B-cell lymphomas, including pre-B-cell lymphoma; Burkitt-like lymphoma; malignant lymphoma, small lymphocytic; the many forms of germinal center cell-derived lymphomas; immunocytoma; plasmacytoma; and immunoblastic lymphoma (B type)-may involve the skin and can be classified according to modern lymphoma classifications.

[Pathological re-evaluation of cases of chronic lymphoid leukemia]

Lymph nodes of 46 autopsy cases regarded clinically on the basis of bone marrow and blood film findings as chronic lymphoid leukaemia were reinvestigated. Considering the new reclassification of malignant lymphomas only 38 per cent of the cases have shown histologic pattern of chronic lymphoid leukaemia. 28 per cent out of the remaining 62 proved to be lymphoplasmocytic immunocytoma, 10 per cent centroblastic-centrolytic ML and 8 per cent centrocytic ML.

A critical analysis of the classifications of non-Hodgkin's lymphomas

The Rappaport classification of non-Hodgkin's lymphomas was proposed almost a quarter century ago, before the advent of modern immunology. This classification, which is based entirely on morphologic features, has proved its clinical usefulness. In light of recent scientific advances, however, its terminology is not appropriate. Five new classifications have been proposed recently, each claiming to have more merit than the others. The purpose of this study is to critically analyze and evaluate these newly proposed classifications to determine which classification is conceptually and scientifically acceptable as well as clinically useful. The results of the study show that there are more similarities than differences among the Rappaport. Lukes and Collins, Dorfman, British, and WHO classifications; the Kiel classification, however, is fundamentally different (Tables 8, 9, 11). None of these classifications can be used in its proposed form. Based on the analysis of these classifications, a compromise working classification is proposed which incorporates the relevant concepts and terminology from the Rappaport, Berard, Dorfman, WHO, and Lukes and Collins classifications (Tables 15, 16). The proposed compromise classification is an attempt to reconcile the various classifications, and to stimulate others to offer modifications which may bring about a final solution to the problem of classification of non-Hodgkin's lymphomas.

Plasma cell neoplasia with osteosclerotic lesions. A study of five cases and a review of the literature

Sixty-eight patients with plasmacytic neoplasia and osteosclerotic lesions were analyzed. Men predominated in this series. Mean age was 55.3 years and 26 patients were younger than 51 years at diagnosis. Early onset of disease was statistically different from multiple myeloma in general. Thirty patients had peripheral polyneuropathy and often neurological manifestations preceded other symptoms. Skeletal pain was less common, whereas hepatomegaly, splenomegaly, and lymphadenopathy were more common than in myeloma in general. Incidence of azotemia, hypercalcemia, high ESR, and anemia was lower than in myeloma. In one fourth of the patients, the number of skeletal lesions did not exceed three. Mean survival was less than 20 months from first symptom and 12 months from diagnosis. Mortality was related sometimes to polyneuropathy. Thus, in several aspects, plasmacytic neoplasia with osteosclerotic lesions is different from the classical multiple myeloma.

Solitary plasmacytoma of bone vs. extramedullary plasmacytoma and their relationship to multiple myeloma

Solitary plasmacytoma of bone (SPB) and extramedullary plasmacytoma (EMPC) are unusual solitary tumors of plasma cell origin. The clinical differences between these tumors and multiple myeloma are the subject of continued study. This review examines the radiotherapy experience at M. D. Anderson Hospital. Between 1948 and 1977, 12 patients with SPB and 12 patients with EMPC were treated with radiotherapy. Radiotherapeutic doses were most often (22/24) greater than 4,000 rads, at 200 rads per day. In order to qualify as solitary plasmacytoma a disease-free interval of 3 years was required. In the group of SPB, 5 patients of 9 were alive with no evidence of disease (NED) at 3 years, 4 of 5 at 5 years, and none of 4 at 10 years. In the EMPC group, 8 patients of 11 were NED at 3 and 5 years, and 6 of 9 at 10 years. Six patients with SPB developed multiple myeloma compared with only two with EMPC. The results confirm the better prognosis of EMPC and support the theory that SPB and EMPC are two different entities.

Morphology and classification of malignant lymphomas and so-called reticuloses

There is general agreement as to the definition and subclassification of Hodgkin lymphomas, which is acceptable for practical reasons. However, the nature of the different types of Hodgkin lymphomas needs further consideration. On the other hand, today we are as far from agreement on non-Hodgkin lymphomas as ever before. Earlier European and American classifications have now to be reconsidered in the light of modern concepts of experimental immunology. It has become necessary to apply immunochemical and immunomorphological methods in addition to histological, histochemical, cytological, and ultrastructural techniques. Only such a complex approach has been able to provide new insight into the functional properties of the tumor cells. The result was a new lymphoma classification, which conforms to LUKES' concept in many respects. It was fundamentally accepted by a group of European lymphoma experts and has been condensed and modified in order to be applicable by as many lymphoma centers as possible. It has received the name "Kiel Classification" 1974. The main principles of the classification are as follows: 1. A distinction is made between malignant lymphomas of low-grade and those of high-grade malignancy; "-cytic", "-blastic" m.l. 2. The terms "sarcoma" and "leukemia" are avoided. All types of malignant lymphoma can be leukemic, however with differnt frequencies. All B-cell lymphomas can also show a monoclonal immunoglobulin increase ("paraproteinemia") in the blood, mostly of IgM. So-called macroglobulinemia of Waldenström is therefore not itself an etity, but instead a clinical syndrome. It has been shown that so-called reticulosarcoma is derived from immunoblasts, not from reticulum cells or histiocytes. The group of reticuloses also needs reconsideration. The term "reticulosis" is cytologically incorrect in most cases. Otherwise it refers to a group of diseases which we do not yet understand.