Morphological subclassification of follicular lymphoma: variability of diagnoses among hematopathologists, a collaborative study between the Repository Center and Pathology Panel for Lymphoma Clinical Studies.

A collaborative study between the Repository Center for Lymphoma Clinical Studies and the members of the lymphoma pathology subcommittee of the major cooperative oncology groups was undertaken in an effort to ascertain the reproducibility and the interobserver agreement for the cytologic diagnosis of follicular lymphomas. A group of 105 patients with follicular lymphomas were subclassified by seven hematopathologists according to two methods. In the first method, cases were subclassified according to the Rappaport, Lukes, and Collins, and Working Formulation systems. In these systems, follicular lymphomas are subclassified by estimation of the different cell populations without the actual counting of cells. With this method, great variability in diagnosis was noted. For example: (1) The consensus diagnosis was that of poorly differentiated lymphocytic lymphoma (PDL) in 39 cases, but among the individual pathologists the number of cases thus diagnosed ranged from 24 to 65; (2) In 40 cases, the consensus diagnosis was follicular lymphoma, mixed-cell type; however, all seven pathologists independently agreed on this subtype in only one case; (3) A major disagreement was noted in 39 cases (37%), in which both diagnostic extremes (small cleaved and large noncleaved) were expressed. In the second method, only precise counts of different cells were made, according to a modification of the method recommended by Berard. With this counting method, diagnoses were independently derived based on the counts provided by the seven pathologists for large cleaved, small noncleaved, and large noncleaved cells. The variability in the results was wide also with this second method. For example, the average number of large cells found by each pathologist was ascertained, and the ranges were determined. The average range was 28 cells, which was considered high. The same determinations were performed only for large noncleaved cells, and the range was found to be 15 cells, which was also considered high. When the diagnoses derived from counts of only large noncleaved cells were compared with the traditional, more subjective diagnoses, fairly close agreement was obtained. In summary, the great variability in diagnoses of follicular lymphomas among pathologists may be attributed to the difficulties inherent in accurate determination of cell size and of the precise percentages of different cells. Until solutions to these problems are developed, one can subclassify follicular lymphomas according to the Berard method or the estimation method.

Atypical lymphoplasmacytic and immunoblastic proliferation in lymph nodes of patients with autoimmune disease (autoimmune-disease-associated lymphadenopathy).

This study is based on an analysis of the morphologic, clinical, and laboratory findings in 26 patients whose pretherapy lymph node biopsies showed some, but not all, of the diagnostic features of angioimmunoblastic lymphadenopathy with dysproteinemia (AILD). Partial or complete effacement of nodal architecture by a diffuse lymphoplasmacytic and immunoblastic proliferation was a constant histologic finding. In contrast to the findings in AILD, lymphocytic depletion and pronounced arborizing vascular proliferation were often lacking. Clinically, many of the patients had fever, sweats, weight loss, skin rashes, generalized lymphadenopathy, hepatosplenomegaly, and, in some cases, pulmonary infiltrates. Of the 26 patients, 23 had clinical and/or laboratory evidence of autoimmune disease or immune complex disease. In 12 patients (Group I--idiopathic), various autoantibodies or immune complexes were demonstrable, but these patients did not manifest a well-defined immunologic disease or syndrome. In 11 patients (Group II--secondary), the lymphadenopathy occurred secondary to a well-defined, clinically recognized immunologic disease. Three patients (Group III) had neither a well-defined autoimmune disease nor demonstrable autoantibodies, but two of them had a history of exposure to antibiotics. We suggest that patients whose lymph nodes have the morphologic features described here frequently have an autoimmune disorder, and that the pathogenesis of this clinicopathologic picture is probably related to a deficiency in suppressor T-cell function which results in an unopposed proliferation of B cells with autoantibody formation and polyclonal gammopathy. Our observations should stimulate clinicians to consider the possibility of an autoimmune pathogenesis for a lymphadenopathy in which a florid lymphoplasmacytic and immunoblastic proliferation similar to that observed in AILD is demonstrated, even though the sections may not meet all the histologic criteria reported for the diagnosis of AILD. Clinical and laboratory investigations necessary to confirm the presence of autoimmunity are indicated in these cases. Moreover, since there is evidence of genetic factors predisposing to autoimmune disease (17, 43), it would be important to investigate close relatives of patients whose lymph nodes showed the histologic changes described in this paper in prospective studies which include suppressor T-cell function, autoantibodies, HLA type of blood lymphocytes and chromosomal analysis. The median survival of the 23 patients with stigmata of autoimmune disease or immune complex disease was 36 months.(ABSTRACT TRUNCATED AT 400 WORDS)

Whipple's disease of the lung.

Described here is a unique case of Whipple's disease in a 54 year old man with chronic severe cough and gastrointestinal symptoms in whom the initial diagnosis of Whipple's disease was made by lung biopsy. This is, to our knowledge, the first reported case in which the bacilliform structures of Whipple's disease have been demonstrated in tissues from other than the gastrointestinal tract of lymph nodes. Subsequently, a peroral biopsy of the small intestine was performed and revealed identical and pathognomonic features of Whipple's disease. The pulmonary roentgenologic findings are described and the histologic differential diagnosis of histiocytic infiltrates in the lung, which may be histologically similar to Whipple's disease, are briefly reviewed.

Distinction between undifferentiated (small noncleaved) and lymphoblastic lymphoma. An immunohistologic study on paraffin-embedded, fixed tissue sections.

The morphologic differentiation between malignant lymphoma of the small noncleaved cell (SNC) type and lymphoblastic lymphoma (LBL) is at times difficult, particularly when fresh tissue is not available for immunologic studies. We have examined the reactivities of a panel of monoclonal and polyclonal antibodies, including LN-1, LN-2, and antibodies to immunoglobulin light chains, leukocyte common antigen (LCA), Leu-M1, vimentin, S-100 protein, lysozyme, and alpha-1-antitrypsin, in paraffin-embedded, B5- and formalin-fixed tissue involved by SNC or LBL. The immunophenotypes in all of the cases included in this study had been characterized previously in fresh-frozen sections or cell suspensions. Among 21 samples of B5-fixed SNC, LN-1 was reactive in 17 and LN-2 in 18 cases. Among 13 B5-fixed LBL, LN-1 was reactive in two cases and LN-2 was reactive in two cases. Each of 20 B5-fixed samples of SNC was reactive with at least one of the antibodies, whereas 10 of the 13 B5-fixed samples of LBL were negative for both antibodies. Lesser reactivity was evident in formalin-fixed tissues, with only nine of 27 SNC specimens positive for LN-1 and 16 of 27 positive for LN-2. Most or all of the SNC and LBL samples were negative for immunoglobulin light chains, Leu-M1, vimentin, S-100 protein, lysozyme, and alpha-1-antitrypsin. The majority of both SNC and LBL were positive for LCA. We conclude that LN-1, preferably in combination with LN-2, can be used for distinguishing between SNC and LBL in paraffin-embedded, B5-fixed tissue when fresh tissue is not available.

Enzymatic differences between chronic lymphocytic leukemia and prolymphocytic leukemia.

Chronic lymphocytic leukemia and prolymphocytic leukemia of the B-cell immunophenotype are closely related disorders, but differ in their cytomorphologic and clinical features. In an attempt to differentiate further between these two forms of leukemia, we measured adenosine deaminase and purine nucleoside phosphorylase activities by using a linked-enzyme spectrophotometric assay on peripheral-blood leukemic cells from seven patients with chronic lymphocytic leukemia, three patients with prolymphocytic leukemia, and one patient with prolymphocytoid transformation of chronic lymphocytic leukemia. By using discriminant analysis, we were able to distinguish the two groups only on the basis of purine nucleoside phosphorylase activity (F1,9; p less than 0.001). The purine nucleoside phosphorylase activity in leukemic cells with prolymphocytic cytomorphology was significantly elevated (mean = 58.6 nM/min/mg protein) compared to the activity in leukemic cells with lymphocytic cytomorphology (mean = 25.6 nM/min/mg protein). There was only one patient with chronic lymphocytic leukemia who was assigned to the prolymphocytic leukemia group on the basis of her purine nucleoside phosphorylase activity. Our study suggests that purine nucleoside phosphorylase activity in leukemic cells may be useful in the distinction of prolymphocytic leukemia from chronic lymphocytic leukemia, and that it may be an enzymatic marker for the early detection of prolymphocytoid transformation of chronic lymphocytic leukemia.

The in-vitro response of CD2-positive acute myelogenous leukemia to proliferation and differentiation inducing agents.

Acute mixed lineage leukemias (MLL) are a heterogeneous group of acute leukemias that express morphologic and/or immunophenotypic features of more than one hematopoietic cell line. The ontogenetic significance of this mixed lineage expression is unclear. We therefore studied the conviction of the lineage commitment in a group of MLL by examining the in-vitro response of five CD2+ (E-rosette receptor) acute myelogenous leukemia (AML) to a panel of proliferation and differentiation-inducing agents. Three of the five CD2+ AML were TdT-positive. Antigen receptor gene studies revealed no rearrangements at either the T beta or immunoglobulin heavy chain gene loci in any case. When blast-enriched cell populations were placed in short term suspension cultures with PHA, IL-2, PHA + IL-2, GM-CSF or TPA, three of the leukemias responded in a similar fashion while the remaining two cases showed no response. In the three MLL that responded to the in-vitro culture manipulations, features indicative of differentiation along the monocytic lineage pathway were observed. This differentiation was not pronounced in the presence of the phorbol ester TPA, and was manifested by loss of CD2 and CD7 expression, continued expression of myeloid antigens, and the development by the blasts of morphologic and cytochemical characteristics of monocytic cells. None of the five MLL showed any evidence of induced maturation along the T-lymphocyte line of differentiation with any of the agents used. rGM-CSF was the only exogenously added agent to induce proliferation; the proliferative response was slight and was seen in only one of the five leukemias. Therefore, the phenotypic expression of CD2 and CD7 in blasts from MLL is not indicative of irreversible commitment to T-lymphocyte development. The in-vitro loss of T-cell antigens in concert with the development of monocytic features in three of the five CD2+ AML in this study suggests the leukemic cells were preferentially committed to a non-lymphoid lineage differentiation pathway.

Lymphoblastic lymphoma expressing natural killer cell-associated antigens: a clinicopathologic study of six cases.

We describe six patients with lymphoblastic lymphoma (LBL) whose neoplastic lymphoid cells expressed surface antigens associated with natural killer (NK) cells. The six cases were selected from a series of 38 specimens diagnosed as LBL based on morphologic criteria and further subclassified by the use of an extensive panel of monoclonal and polyclonal antibodies. Although the morphologic features in all six cases were similar to those previously reported for LBL, their expression of NK-associated antigens was unique. All cases were positive with anti-Leu 11b, an antibody which appears to define a specific subtype of lymphocytes considered to have NK function; and all cases expressed T11, a T-cell-restricted antigen. The most commonly encountered immunophenotype of our cases of LBL was: Leu 11b+, T11+, Leu7+, TdT+, Leu 3a+, Ia+, pre-B-, and B-. As compared with more classical LBL of T-cell type, LBL of NK-cell type in our series occurred primarily in females and non-whites. Whereas treatment of classical LBL by multi-agent chemotherapy may lead to long-term survival, only two of our six patients were long-term survivors. The data derived from this study raise the possibility that LBL with the antigenic phenotype of NK cells may represent a biologic subtype of LBL.

Thorotrast induced hepatic cholangiocarcinoma and angiosarcoma.

A 49 year old woman developed hepatic cholangiocarcinoma and angiosarcoma 22 years after the administration of Thorotrast. The etiologic association between Thorotrast and a variety of malignant hepatic neoplasms is well known, but the simultaneous occurrence of two different hepatic neoplasms has not been previously reported.

Immunohistologic studies of bone marrow biopsies on frozen sections: an analysis of 42 cases.

An immunohistologic study of bone marrow biopsy frozen sections from 42 cases involved by a variety of reactive and neoplastic disorders is presented. Thirteen cases also were studied using other methods, including cytochemistry, surface marker analysis of cell suspensions, and/or DNA hybridization. Thirty-four of 42 cases (81%) were adequately phenotyped on frozen tissue using a panel of antibodies for hematolymphoid-associated antigens. The immunostains from the remaining eight cases were unsatisfactory, primarily as a result of heavy background staining. Eighteen cases were lymphoproliferative disorders of B-cell phenotype and 12 of these showed surface monotypic immunoglobulin expression by the frozen section technique. Six cases showed B- or pre-B-cell antigens but no surface immunoglobulins. Of the remaining 16 patients, two cases showed myeloid markers and three showed T-cell phenotype. Nine cases showed a mixture of polyclonal B- and T-cell populations. Keratin was demonstrated in a single case of metastatic carcinoma included in the study. These results indicate that the majority of hematopoietic processes can be successfully phenotyped on bone core frozen sections and demonstrate the usefulness of immunohistologic study of the frozen bone marrow biopsy specimens, especially when the specimens for other modalities are not available or are inadequate. The keys to achieving the best results from the frozen bone marrow immunohistochemistry were the gentle handling of the specimens and the preparation of high-quality, cryostat-cut frozen sections.

Multicentric angiofollicular lymph node hyperplasia: a clinicopathologic study of 16 cases.

A clinicopathologic analysis of 16 cases of multicentric angiofollicular lymph node hyperplasia (MAFH) was performed. Histologically, the disease was characterized by recognizable lymph node architecture that was at least partially intact, by paracortical hyperplasia with prominent vascular proliferation, and by numerous evenly distributed, apparently benign germinal centers of various types, usually including some typical hyaline-vascular centers. At the onset of the disease, 12 patients had the plasma cell (PC) type of MAFH, three patients had the hyaline-vascular (HV) type, and one patient presented with PC and HV types at separate sites. Transitions between the PC and HV types were observed in two cases. Immunologic studies demonstrated polyclonal populations of plasma cells in the lymph nodes of all patients and the absence of suppressor T lymphocytes in the one patient tested. Clinically, the patients had constitutional symptoms, multicentric lymphadenopathy, hepatosplenomegaly in many cases, and abnormal laboratory findings, including anemia, polyclonal hypergammaglobulinemia, and bone marrow plasmacytosis. The 16 patients were placed in four different clinical groups based on presentation and course: stable disease, chronic relapsing disease, aggressive disease, and development of malignant lymphoma. Ten of the 16 patients died (median survival, 26 months; range, eight to 170 months). Multicentric angiofollicular lymph node hyperplasia appears to be a variant of classic angiofollicular lymph node hyperplasia (Castleman's disease) and is associated with significant morbidity and mortality.

Monocytoid B lymphocytes: their relation to the patterns of the acquired immunodeficiency syndrome (AIDS) and AIDS-related lymphadenopathy.

It was shown recently that monocytoid cells express B-cell-restricted antigens and polyclonal surface immunoglobulins, and the term monocytoid B lymphocytes (MBL) has thus been offered as a more appropriate designation. Although most commonly seen in toxoplasmic lymphadenitis, MBL have been observed in a variety of reactive and neoplastic conditions involving lymph nodes. In the present study MBL were found in 17 of 22 lymph nodes from 20 patients with the acquired immunodeficiency syndrome (AIDS) and AIDS-related lymphadenopathy. In all 17 samples, the MBL were found in lymph nodes with florid reactive follicular hyperplasia, and they were geographically close to the hyperplastic lymphoid follicles. However, MBL were not detected in lymph nodes showing involuted follicles or lymphocyte depletion. The disappearance of MBL apparently parallels the progressive involution of secondary follicles. Leu-3+/Leu-2+ (T-helper/T-suppressor) ratios were studied in 14 lymph node cell suspension samples and ten peripheral blood samples. The lymph node Leu-3+/Leu-2+ ratios were significantly lower in AIDS-related lymphadenopathy than in non-AIDS-related reactive follicular hyperplasia (P less than 0.001); the peripheral blood ratios were decreased in nine of the ten cases. The diminished T-helper status in patients with AIDS and AIDS-related lymphadenopathy may be relevant to the immunopathogenesis of follicular involution and, indirectly, to the disappearance of MBL.

Angiotropic large cell lymphoma of the prostate gland: an immunohistochemical study.

Malignant angioendotheliomatosis (MAE) is a rare disorder characterized by the intravascular proliferation of neoplastic mononuclear cells. Until recently, the cell of origin was uncertain; some investigators reported MAE to be lymphomatous in nature, while others claimed it to be of endothelial derivation. In the present unusual case, MAE was an incidental findings in the prostate of a patient with prostatic adenocarcinoma; it is shown to be a lymphoma of B-cell origin.

Monoclonal small (well-differentiated) lymphocytic proliferations of the gastrointestinal tract resembling lymphoid hyperplasia: a neoplasm of uncertain malignant potential.

Three histologically benign-appearing or diagnostically equivocal small lymphocytic proliferations of the gastrointestinal tract were examined by fresh-frozen section immunohistologic techniques. In one case, a dense infiltrate in the small intestine, consisting of small lymphocytes with round nuclei, was limited almost entirely to the mucosa. In another case, a localized colonic polyp was formed by mucosal and submucosal lobules of benign-appearing lymphoid aggregates with centrally located germinal centers. The third case, a penetrating gastric ulcer, was surrounded by histologically hyperplastic lymphoid tissue which included germinal centers. The small lymphocytes in all three cases were strongly positive for B-cell-associated antigens (B1, B2, BA-1), and all exhibited monoclonal light-chain restriction. Even though treatment consisted only of surgical resection of the lesions, no patient has had progressive disease during follow-up periods ranging from 24 to more than 50 months. We believe that the infiltrates in these cases are analogous to the morphologically benign monoclonal small lymphocytic proliferations common to the lung and orbit and that they have an uncertain, but probably low, malignant potential.

Concurrent presence of two clonal populations in small lymphocytic lymphoma of the lung.

In a patient with small lymphocytic proliferation (SLP) involving the right middle and right lower lobes of the lung, immunophenotypic studies showed that the neoplastic lymphoid cells in the right middle lobe expressed kappa light chains, whereas those in the right lower lobe expressed lambda light chains on their surface. Gene rearrangement studies with Southern-blot hybridization confirmed the disparate surface immunoglobulin expression, and showed that the SLPs in the two lobes were derived from separate clones. The findings indicate that even morphologically identical lymphomas in the same organ may be immunophenotypically and genotypically heterogeneous. Our findings demonstrate that immunologic and DNA gene rearrangement analyses may complement each other in the study of lymphomas. This case is unique in that it is the first reported case of the concurrent presence of two immunologically distinct clonal populations in an extranodal site.

Imprint cytology of non-Hodgkin's lymphomas based on a study of 212 immunologically characterized cases: correlation of touch imprints with tissue sections.

The classification of non-Hodgkin's lymphomas (NHLs) has been traditionally based on analysis of histologic sections and has been supplemented more recently by immunologic marker studies. It was the purpose of the present study to illustrate, side-by-side, sections and Romanowsky-stained imprints from the same surgical specimen from practically all categories of immunophenotyped NHLs, including rare and atypical variants that were difficult to classify from the histologic sections alone. Our results indicate that imprint cytology may reveal nuclear and cytoplasmic details not discernible in even the best tissue sections and that it may be selectively helpful in contributing to the classification of NHLs. Our results also show that the relative value of imprint cytology in the classification of malignant lymphomas varies greatly among categories. Specifically, we have found that imprints assist in three ways: the recognition of plasmacytoid features in small cell lymphocytic lymphomas, the recognition of plasmacytoid immunoblastic lymphoma, and the differentiation between NHLs which may be difficult to distinguish histologically. These include (1) small lymphocytic lymphoma versus lymphocytic lymphoma of intermediate differentiation, (2) true histiocytic malignancies versus large cell malignant lymphomas with abundant cytoplasm and/or phagocytosis, (3) anaplastic myeloma versus plasmacytoid immunoblastic lymphoma, (4) large noncleaved versus plasmacytoid immunoblastic lymphoma, (5) lymphoblastic lymphoma versus diffuse small cleaved cell lymphoma, and (6) lymphoblastic lymphoma versus small noncleaved cell lymphoma. Lymph node imprints are easy to prepare and readily interpretable by those experienced in the study of abnormal blood and bone marrow films. Their value as an ancillary methodology aimed at optimal accuracy in the classification of NHLs should be recognized.

Neoplastic B cells with cerebriform nuclei in follicular lymphomas.

Three cases of follicular lymphoma in which the follicular center cells exhibited pronounced nuclear irregularities, i.e., convoluted and cerebriform shapes, are described. The cytoplasm in B5-fixed sections was scanty to abundant and showed pale to clear staining, with interlocking cell borders. Although the architectural pattern in these cases suggested B-cell lymphoma, the cytologic features suggested a T-cell phenotype. Immunologic studies of frozen sections by immunohistochemical techniques in all three cases, as well as cell suspension studies in two cases, showed that the follicular center cells, including those with convoluted and cerebriform nuclei, were clearly monoclonal B cells, as evidenced by the presence of only one immunoglobulin light chain on the surfaces. The results of this study suggest that the follicular architectural pattern is a more reliable predictor of the immunologic phenotype than are the cytologic features.

Genotype and phenotype: a practical approach to the immunogenetic analysis of lymphoproliferative disorders.

Determination of cell lineage and clonality in lymphoproliferative disorders (LPD) is greatly enhanced by molecular genetic analysis in conjunction with morphologic and immunologic techniques. We now report on a technique in which we used cryostat-cut, fresh-frozen sections (CCFFS) prepared from tissues in a manner that allows DNA hybridization studies to be coordinated readily with routine morphologic and immunohistologic studies. Thirty-seven cases representing a broad spectrum of reactive and malignant LPD were examined with this method. Samples of DNA were extracted from frozen sections, subjected to Southern blot hybridization, and probed for rearrangements of the immunoglobulin (Ig) heavy-chain and the kappa and lambda light-chain genes, as well as for the T-cell receptor beta-chain gene. We also evaluated the effects of (1) diagnostic category of LPD, (2) volume of the tissue sample, and (3) fibrosis, necrosis, and ice crystal artifacts in the sample on the recovery of DNA. Ice artifact and sample size had the greatest negative impacts on the quantity and condition of DNA recovered. Of 19 samples involved by B-cell LPD, the results of immunogenetic studies were consistent with the immunophenotypes in all but one case. Of the T-cell lymphomas from which sufficient DNA was available (three out of five of the T-cell cases), all showed rearrangements of the T-cell beta-chain gene. In order to reduce sample processing time, we evaluated alternate blot hybridization methods, rapid alkaline transfers, and direct hybridization of synthetic oligonucleotides in dried agarose gels, and found that they decreased the time required for hybridization studies. In summary, the use of CCFFS as the source of DNA allows study of gene rearrangements and, at the same time, preserves frozen-tissue blocks in tumor banks for further immunologic studies. The development of time-effective methods will make the routine use of molecular-genetic analysis more practical in the diagnostic hematopathology laboratory.

Immunoarchitecture of normal human bone marrow: a study of frozen and fixed tissue sections.

To provide baseline information on the immunoarchitecture of normal bone marrow, we studied cryostat-cut, frozen, and paraffin-embedded, fixed tissue sections prepared from 21 core biopsies of normal bone marrow obtained during bone marrow harvests for transplantation. A large panel of antibodies was applied that included, for frozen tissue, Leu-6 (CD1), T11 (CD2), Leu-3a (CD4), Leu-1 (CD5), Leu-2a (CD8), J5 (CD10), My7 (CD13), Leu-11 (CD16), B4 (CD19), B1 (CD20), B2 (CD21), Tac (CD25), My9 (CD33), T200 (CD45), NKH-1 (CD56), kappa and lambda chains, beta F1, Ki-67, HLA-DR, TQ1, and keratin, and for fixed tissue, leukocyte common antigen (CD45), L26 (CD20), LN1 (CDw75), LN2 (CD74), LN3, LN4, LN5, MB1 (CD45R), MB2, MT1 (CD43), MT2 (CD45R), UCHL1 (CD45R0), BM1, Ki-1 (CD30), Leu-M1 (CD15), lysozyme, KP1 (CD68), actin, S100, neuron-specific enolase, vimentin, and keratin. On fresh-frozen sections CD19 and CD2 were the most reliable and sensitive markers for B and T cells, staining 5% and 9% of marrow cells, respectively. Immunoglobulins generally showed heavy background staining, which frequently precluded an accurate assessment. The CD4 to CD8 ratio in the bone marrow was reversed from that of peripheral blood. On fixed tissues, leukocyte common antigen was found in 14% of the marrow cells, corresponding roughly to the lymphocyte population. L26, a pan-B-cell marker, stained 3% of the marrow cells. Among the other B-cell markers, LN1 and MB2 stained a large number of cells (40% to 70%), indicating reactivity with cells of the myeloid or erythroid series in addition to lymphocytes. Among the T-cell markers, UCHL1 and MT1 stained 66% and 50% of the cells, respectively, which could be explained by their cross-reactivity with myeloid cells. Nonspecific myelomonocytic markers (Leu-M1, KP1, and lysozyme) also showed reactivity in a high percentage of cells. No particular architectural distribution patterns of B or T lymphocytes were noted in either frozen or fixed bone marrow specimens. The results of this study provide normal baseline data for the immunohistologic application of hematopoietic and lymphoid markers on frozen or fixed bone marrow biopsy specimens.

Mitotic counts in follicular lymphomas.

Increased mitotic activity is associated with significantly shorter patient survival in some of the subtypes of diffuse non-Hodgkin's lymphomas. This study on 105 cases of follicular lymphoma was undertaken to determine the clinical significance of mitotic activity in follicular lymphomas. For each case, two pathologists independently counted mitotic figures in 20 random high-power fields. The difference of the average mitotic counts over 20 high-power fields for the two pathologists showed a Gaussian distribution with a median difference of -0.26 counts per high-power field and a standard error of 0.10 per cent. In 94 cases (91 per cent), the difference was less than two mitotic counts per high-power field, indicating good interobserver agreement. There was a statistically significant difference in mitotic counts between subtypes of follicular lymphoma as well as a gradient among subtypes, with the lowest mitotic activity in the poorly differentiated lymphocytic subtype and highest in the undifferentiated subtype. A multivariate statistical analysis of clinical and pathologic variables showed that mitotic figures were not of prognostic significance.

Recognition of hairy cell leukemia in a spleen of normal weight. The contribution of immunohistologic studies.

A 68-year-old man with known hairy cell leukemia (HCL) underwent splenectomy; the spleen weighed only 140 g. Microscopic examination of the spleen revealed no clear diagnostic evidence of HCL, but there was an unusual and suspicious subendothelial lymphoid infiltration of the trabecular veins. Cell suspension studies also were not diagnostic because a monoclonal B-cell population could not be defined. Alternatively, when we focused on the subendothelial infiltrate in the frozen sections prepared for immunohistochemical studies, the findings indicated that the subendothelial cells were monoclonal B-cells (IgG, kappa). Staining with monoclonal antibodies disclosed the phenotype Tac+, Leu-14+, Leu-M5+, B2-, BA-1-, and BA-2-, a phenotype characteristic of HCL. In this case, an unusual but nondiagnostic morphologic finding provided guidance for the correlative immunophenotypic analysis of the same site in frozen sections and thereby allowed a definitive diagnosis.