Paraffin section immunohistochemistry. I. Non-Hodgkin's lymphoma

Herpesvirus-associated lymphomas: Investigations in humans and animal models

Lymphomas are solid tumors consisting of lymphoid cells; they form a heterogeneous group of less or more malignant disorders. A portion of lymphomas develop due to latent herpesvirus infections established in B and/or T-lymphocytes. The basis for latency is a lifelong presence of the circularized covalently linked viral genome within nuclei of carrier lymphocytes. In certain cases, however, the essential event leading to tumor formation is the integration of a portion(s) of viral DNA into the host cell DNA. This leads to rearrangements within the host cell genome on one hand, and, on other hand, to unregulated expression of oncoproteins encoded by the integrated fragment. Our review deals with mechanisms of lymphoma formation regarding to the role of non-structural herpesvirus oncoproteins interfering with the regulation of cell division and/or exerting anti-apoptotic effects. In addition, the authors wish to highlight the common procedures, which allowed isolation and/or identification of lymphoma-associated viruses in cell cultures derived from tumors and/or proliferating lymphatic tissues.

A three-dimensional organotypic culture of the human uterine exocervix for studying mucosal epithelial differentiation and migrating leukocytes

We report on a three-dimensional organotypic culture in vitro of explants from the human uterine exocervix. Exocervical fragments (2-3 mm3) from pre-menopausal women were cultured on sponges submerged in Dulbecco's Modified Eagle's Medium containing p-nonylphenol and 10% fetal bovine serum for up to 3 weeks and the viability and cellular responses were assayed. The fragments were analyzed by immunohistochemistry for the expression and distribution of a broad spectrum of cellular markers: p63, Ki-67, involucrin, high molecular weight cytokeratins, estrogen receptor-alpha, vimentin, CD45, and CD31. The fragments preserved their tissue architecture and cellular heterogeneity comparable to that observed in exocervical tissue in vivo. Prior to culture, the original epithelium was composed of stratified multilayered keratinocytes with integrated monocyte/dendritic-like cells in the basal and suprabasal layers. The epithelium began to exfoliate in culture and within 4 days appeared to have lost its differentiated high-zone layers of keratinocytes. After 10 days a new epithelium, slightly different from the original one, was formed; it displayed an increasing prominence of basal and suprabasal keratinocyte layers, containing infiltrating leukocytes that had probably migrated from the submucosa. The epithelium subsequently lost its organization, concomitant with a progressive involution of the stroma. Subepithelial capillaries appeared to be well maintained throughout the culture period. Aside from the maintenance of cellular heterogeneity within the fragments of exocervix, these culture systems are a valuable tool for studying the mechanisms of epithelial regeneration, and may prove to be a useful model for studying mucosal immunity.

Malignant mesothelioma with CD30-positivity. A case report and review of the literature

The activation marker CD3O is useful in the diagnosis of Hodgkin and non-Hodgkin lymphomas. It has also been described in nonhematopoietic tumors, including pancreatic carcinomas, salivary gland tumors, and embryonal carcinomas. We report a case of malignant mesothelioma with intense CD30 positivity. This finding has not previously been described and is important in broadening the differential diagnosis of a CD30(+) cohesive large cell malignancy.

Analysis of the promoter of the MUC1 gene overexpressed in breast cancer

The MUC1 gene encodes a mucin glycoprotein and is overexpressed in breast cancer. Knowledge of the mechanisms leading to MUC1 overexpression may help in the development of molecular approaches for breast cancer therapy. In order to study the regulation of the MUC1 gene transcription, we analyzed functional activities of various deletion mutants of the MUC1 promoter. We established that transcriptional cis-elements present in the SacI/XmnI fragment of the promoter are competent and sufficient for expression of, at least, tandem repeats containing isoform(s) of the MUC1 protein. CAT transfection analysis showed that both the 3' and 5' regions of the SacI/XmnI fragment possess transcription activities. Promoter activities associated with the SacI/XmnI fragment were confirmed by a RNase protection assay, which demonstrated multiple transcription start sites (TSSs) in the MUC1 gene transcribed in epithelial T47D cells. We show that treatment of the T47D cells with TGFbeta1 leads to activation of additional TSSs in the MUC1 gene. The roles of the structural and functional properties of the MUC1 promoter in MUC1 gene transcription are discussed.

Paraffin immunohistochemistry as an adjunct to hematopathology

In the past two decades, there have been a number of dramatic advances in immunology that have subsequently affected immunohistochemistry. These have had a substantial impact on all phases of laboratory medicine, especially surgical pathology. Many hospital laboratories use immunohistochemical analysis on paraffin-embedded tissue sections as routinely as other special histochemical techniques. Hematopathology, in particular, has become increasingly reliant on the immunohistochemical antibody technique. This method aids in the identification of lineage-associated or lineage-restricted antigens in hematolymphoid neoplasms. The demonstration of kappa or lambda light-chain restriction is a good indicator of monoclonality in B-cell processes, aiding in the distinction between benign reactive hyperplasia and malignant lymphoma. Increasing numbers of antibodies that react to cluster differentiation cell surface antigens have become available for use in paraffin-embedded sections, obviating the need for frozen tissue in many cases. This facilitates the collection, processing, shipping, and storage of tissue specimens for immunohistochemical studies. This report will discuss the basic concepts in the immunohistochemical technique and show its applicability to hematopathology. It will also describe the most relevant antigens/antibodies and how they are used in antibody panels for the diagnosis of benign and malignant hematolymphoid lesions.

Practical applications of immunohistochemistry in hematolymphoid neoplasms

Immunohistochemistry plays a key role in the diagnosis and classification of hematolymphoid neoplasms. New cell and lineage markers are constantly being discovered and added to the existing long list of antibodies. In this review article we provide general information and new applications of the commonly used hematolymphoid markers. We also discuss the features and applications of some newly discovered markers, such as ALK, fascin, granzyme/perforin, and tryptase. There is no universal "panel" for the diagnosis of hematolymphoid neoplasms. However, in this review article, we provide suggested panels for a given hematolymphoid neoplasm that is based on our experience and that reported in the literature.

Expression of MUC-1 glycoprotein in plasma cells, follicular dendritic cells, myofibroblasts and perineurial cells: immunohistochemical analysis using three monoclonal antibodies

Normal and malignant plasma cells (PC), follicular dendritic cells (FDC), myofibroblasts (MFB) and perineurial cells (PNC) were investigated for the expression of MUC-1 glycoprotein (MUC-1gp) by immunohistochemical and immunoelectron microscopic techniques using monoclonal antibodies E29, 115D8, DF3 and a combination of the three. MUC-1 glycoprotein-positive PC detected by the combined antibodies were frequently seen in a variety of pathological lesions tested, including chronic cervicitis, chronic synovitis, Hodgkin's disease, allergic rhinitis and sinusitis, tuberculous lymphadenitis, foreign body granuloma, multiple myeloma, and chronic tonsillitis. In the lesions containing MUC-1gp-positive PC, the infiltration of immunoglobulin (Ig) E PC and/or IgE-bound mast cells was significantly increased, but MUC-1gp-positive PC did not contain any specific immunoglobulin heavy or light chains. The findings suggest that the expression of MUC-1 gp in PC, although not restricted to IgE-class cells, may be induced in an allergic status. Plasma cells and PNC mainly reacted with the antibodies E29 and 115D8, while FDC and MFB were principally reactive with the antibody DF3. In some cases of multiple myeloma, the neoplastic PC were predominantly immunoreactive with DF3. The results indicate: (i) the epitopic variability of MUC-1gp molecules expressed on the non-epithelial cells; and (ii) the epitopic alterations during malignant transformation. It should also be noted that the expression of MUC-1gp in the non-epithelial cells represents a pitfall in histopathological diagnosis.

Tall cell variant of papillary thyroid carcinoma: a reassessment and immunohistochemical study with comparison to the usual type of papillary carcinoma of the thyroid

A review of 92 consecutive cases of papillary thyroid carcinoma diagnosed at The Methodist Hospital revealed 11 tall cell variant (TCV) cases in nine women and two men. There was a greater average age and larger tumor diameter of TCV cases compared with papillary thyroid carcinoma of the usual type (UPTC), but these differences were not statistically significant. Extrathyroidal extension of tumor was noted in nine of 11 TCV cases and was intraoperatively evident in five cases. The presence of extrathyroidal extension represented a statistically significant difference between TCV and UPTC (p = 0.0001) in a multivariate stepwise logistic regression analysis, with controls for variables of age, sex, tumor size, and lymph node metastases. In 11 TCV patients, tumor recurrence was present in two cases, and there was one tumor-associated death with 1 to 4 years of follow-up. Immunohistochemical stains for thyroglobulin, vimentin, keratins, and Leu-7 were positive in all TCV cases and in 16 of 16 UPTC. Immunoreactivity with antibodies to Leu M1 antigen, a myelomonocytic marker included in cluster designation group (CD 15), which is present in many adenocarcinomas, was present diffusely in all TCV, in contrast to UPTC (with sparse immunostaining in only one of 16 cases). Immunoreactivity with antibodies to ZC-23, an anti-carcinoembryonic antigen (CEA) monoclonal antibody with cross-reactivity to nonspecific cross-reacting antigen and biliary glycoprotein antigen, was present in all TCV but was not present in UPTC. COL-1, a CEA-specific monoclonal antibody, was nonimmunoreactive with all TCV and UPTC cases. Epithelial membrane antigen (EMA) was present in all TCV but was also present focally in eight of 16 UPTC, sometimes in a membranous pattern in epithelium surrounding cystic or hemorrhagic spaces. Strong immunoreactivity with antibodies to Leu M1 and EMA in papillary carcinomas of the thyroid has been associated with advanced stages of disease and tumor-associated mortality. The pattern of immunoreactivity in TCV is dissimilar to that in UPTC and is supportive evidence that TCV is a neoplasm that is distinct from papillary thyroid carcinoma of the usual type.

T-cell-rich B large-cell lymphoma simulating lymphocyte-rich Hodgkin's disease

Immunophenotypic analysis of 50 cases fulfilling the histologic criteria for mixed cellularity Hodgkin's disease disclosed nine cases with a B-cell, non-Hodgkin's phenotype (CD20+, CD15-, CD30-, EMA-). The cases were characterized by a diffuse small lymphocytic milieu, interspersed atypical large cells including classic Reed-Sternberg cells, and infrequent plasma cells, eosinophils, and L&H cells. The male:female ratio was 7:2 (aged 22-65 years, median 39 years). Three patients were Ann Arbor stage II, two stage III, and four stage IV. The patients presented with generalized lymphadenopathy (four), mesenteric lymph node involvement (two), splenomegaly (four), and bone marrow involvement (three). Four patients were treated with standard Hodgkin's disease protocols. Two attained a complete response and two a partial response; all relapsed and died. Four of five patients treated for large-cell lymphoma achieved a complete response and are currently alive without evidence of disease. The one patient with an initial partial response relapsed and died. We conclude that immunophenotypic analysis is essential in cases of histologic mixed cellularity Hodgkin's disease, especially in those with lymphocyte-rich morphology. Cases with a B-cell phenotype should be diagnosed and treated as T-cell-rich B large-cell lymphoma.

Aggressive primary hepatic lymphoma in Chinese patients. Presentation, pathologic features, and outcome

BACKGROUND

Primary non-Hodgkin's lymphoma of the liver is rare. In this study, the presentation, pathologic features, and outcome of seven Chinese patients with primary hepatic lymphoma are described.

METHODS

From 1984 to 1994, the clinical records of 14 Chinese patients with non-Hodgkin's lymphoma and histologically proven liver involvement were reviewed. Seven (four males, three females; median age, 54 years) were considered to have primary hepatic lymphoma. Histologic and immunohistochemical studies were performed on paraffin embedded liver tissue.

RESULTS

"B" symptoms including fever (86%) and weight loss (57%) were the most striking presenting features. Hepatomegaly was present in all patients, splenomegaly in three (43%), and thrombocytopenia in six (86%). Only one patient was hepatitis B surface antigen-seropositive. None had preexisting liver disease. Histologic subtypes, though heterogeneous, were mostly unfavorable and consisted of diffuse large cell lymphoma (two patients), small lymphocytic lymphoma (one patient), lymphoblastic lymphoma (one case), mantle cell lymphoma (one patient), anaplastic large cell Ki-1 lymphoma (one patient), and hepatosplenic T-cell lymphoma (one patient). Three patients expressed B-cell and 2 expressed T-cell phenotypes. Six patients received cytotoxic chemotherapy. One had resection and one had splenectomy, but none achieved complete remission, and only one remained alive as of this writing. The median survival was 3.7 months (range, 8 days to 47.7 months).

CONCLUSION

Chinese patients with primary non-Hodgkin's lymphoma of the liver have prominent "B" symptoms, disease with a highly aggressive course, a poor response to local and systemic treatment, and short survival. Hepatitis B virus infection is not a major etiologic factor for these patients.

CD43 and CD5 antibodies define four normal and neoplastic B-cell subsets: a three-color flow cytometric study

CD43 antibodies are best known for identifying normal and neoplastic T cells and a subset of neoplastic B cells in paraffin sections. The frequency of nonneoplastic CD43 + B cells in different reactive settings, the proportion of B-cell neoplasms with small CD43+ populations, and the relationship of CD43+ B cells was therefore studied in 138 specimens using three-color cytometric analysis. CD43 and CD5 defined four normal B-cell subsets (CD43 + CD5 +, CD43 + CD5-, CD43 - CD5+, and CD43-CD5-). A significantly greater proportion of CD43+ B cells was found in cord blood and putative HIV+ blood samples than in normal control bloods. B-cell neoplasms derived from each of these four B-cell subsets were identified, with CD43+ /CD5+ and CD43-/CD5- neoplasms being most common. The predominant B-cell population coexpressed CD43 alone in 2/39 neoplasms and CD5 alone in four. A minority of cases showed heterogeneous CD43 expression. The B cells in two of three posttransplant lymphoproliferative disorders coexpressed CD43. B cells showed weaker CD43 staining than did T-cells (relative fluorescence 0.38 +/- 0.29). These findings support the concept that CD43 expression by neoplastic B cells is not an aberrant finding. CD43 expression on normal and neoplastic B cells is independent of CD5 expression even though CD43 and CD5 are frequently coexpressed. CD43 expression by B cells sometimes might be underestimated in paraffin sections because it is much weaker than on T cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunophenotypic analysis of childhood Burkitt's lymphoma in the West Midlands 1957-1986

AIMS

To analyse the immunophenotype of a large number of non-endemic Burkitt's lymphomas to determine whether a B cell phenotype is consistently recognisable using formalin fixed, paraffin wax embedded archival material and a standard panel of commercially available antibodies.

METHODS

Archival material was obtained from 30 cases of childhood Burkitt's lymphoma registered with the West Midlands Regional Children's Tumour Research Group. These were analysed by a standard avidin biotin complex immunoperoxidase method using antibodies to CD45, CD43, CD30, CD20, CD15, and immunoglobulin heavy and light chains.

RESULTS

There was a high incidence of the CD45RB and CD20 immunophenotypes, with a clearly recognisable B cell lineage even in archival material. IgM was identifiable in 13 of the 23 (56.5%) cases tested. Only three of 17 (18%) cases expressed CD30. Positive membrane staining with CD45RO was observed in two (6.7%) cases.

CONCLUSIONS

A B cell lineage can be identified in Burkitt's lymphoma in formalin fixed, paraffin wax embedded material, even in archival tissue. There was a low incidence of membrane staining with CD45RO which is a potential source of diagnostic confusion.

The usefulness of cell surface markers in predicting the prognosis of non-Hodgkin's lymphomas

The Working Formulation for classification of non-Hodgkin's lymphomas provides useful prognostic information. Since this scheme was published in 1982, many studies have investigated the prognostic significance of various cell surface markers in lymphoma cases. This article reviews the value of distinguishing T cells from B cells, CD5+ B cells, immunoglobulin light chain types, proliferation antigens such as Ki 67, other markers of B-cell differentiation, and chromosomal anomalies. Each of these contributes some further prognostic significance to that already determined by the Working Formulation.

CD43 expression in B cell lymphoma

AIMS

To determine the expression of CD43 in frozen sections in a range of B cell lymphomas.

METHODS

The monoclonal antibody WR14, clustered provisionally in the Fourth Leucocyte Typing Workshop as a CD43 reagent, was investigated by epitope blocking studies on formalin fixed reactive lymph node tissue, using the established CD43 antibody MT1, to validate its use as a CD43 reagent. CD43 expression was studied in 131 immunophenotypically defined B cell lymphomas, including lymphocytic lymphoma (Lc, n = 13), centrocytic lymphoma (Cc, n = 14), and a range of follicle centre cell lymphomas (FCC) including centroblastic/centrocytic follicular (CbCcF, n = 48), centroblastic diffuse (CbD, n = 39), centroblastic/centrocytic diffuse (CbCcD, n = 4), centroblastic follicular and diffuse (Cb FD, n = 3) and centroblastic/centrocytic follicular and diffuse (CbCc FD, n = 1). Nine lymphomas of mucosa associated lymphoid tissue (MALT) were also examined.

RESULTS

Epitope blocking studies showed that WR14 is a CD43 reagent that binds to an epitope identical with or close to that recognised by MT1. Eleven of 13 (84%) cases of Lc and 11 of 14 (78%) cases of Cc expressed CD43; 87 of 95 (91%) cases of FCC did not. All eight low grade lymphomas of MALT were negative. One high grade lymphoma, transformed from a low grade MALT lymphoma, was positive for CD43. The expression of CD43 by tumours of B cell lineage was associated with the expression of CD5 (p < 0.001) although either antigen could occasionally be found in the absence of the other.

CONCLUSION

CD43 reagents can be used in conjunction with CD5 antibodies for the immunophenotypic discrimination of follicle centre cell lymphomas from non-follicle centre cell lymphomas.

Monoclonal antibody OPD4 detects neoplastic T cells but does not distinguish between CD4 and CD8 neoplastic T cells in paraffin tissue sections

Monoclonal antibody (MoAb) OPD4, reported to preferentially react with benign CD4 T cells in formalin-fixed tissue sections, was examined for its reactivity with 56 T-cell neoplasms after formalin or Bouin's fixation to determine if it also preferentially detects neoplastic CD4 T cells in paraffin tissue sections. Monoclonal antibody OPD4 did not preferentially detect neoplastic CD4 T cells, since it reacted with 22 of 38 (58%) CD4-positive compared with nine of 14 (64%) CD4-negative T-cell neoplasms. However, MoAb OPD4 appears to detect neoplastic T cells in Bouin's-fixed (11 of 20 cases [55%]) about as well as in formalin-fixed (20 of 32 cases [63%]) tissues. Since MoAb OPD4 does not preferentially react with neoplastic CD4 T cells, the utility of this MoAb as a pan-T-cell marker in routinely processed tissues was also explored and compared with that of Leu-22, UCHL-1, and CD3. All four antibodies reacted with approximately the same percentage of T-cell malignancies (51% to 57%). However, examination of different clinicopathologic groups and types of fixative highlighted differences. Monoclonal antibodies OPD4 and Leu-22 reacted with 62%, while CD3 detected only 41% of formalin-fixed, postthymic T-cell neoplasms. OPD4, UCHL-1, and CD3 each reacted with 55%, but Leu-22 recognized only 45% of Bouin's-fixed, postthymic T-cell malignancies. OPD4 reacted with none, but CD3 reacted with all four T-cell lymphoblastic lymphomas. Various antibody combinations were examined to determine an optimal panel for the recognition of T-cell neoplasms in paraffin sections. The combination of MoAbs OPD4 and Leu-22 detected 86% of postthymic T-cell neoplasms in formalin-fixed tissue sections. Furthermore, MoAb OPD4 appears to be relatively specific for T-cell neoplasms, detecting 31 of 56 (55%) T-cell malignancies, while only reacting with two of 39 (5%) B-cell neoplasms. Therefore, while not preferentially reactive with neoplastic CD4 T cells, MoAb OPD4 may be useful as a pan-T-cell marker of postthymic T-cell neoplasms in routinely processed, formalin-fixed tissues, especially when used in conjunction with MoAb Leu-22.

T-cell lymphoma in Singapore: pathology, clinical findings and association with HTLV-1 antibodies

Of 128 cases of malignant lymphomas studied in Singapore between 1986 and 1988, 28 were identified as peripheral T-cell lymphomas. Sera from two of the 128 cases were positive for HTLV-1 antibodies and both cases had the clinical and pathological features of adult T-cell leukaemia/lymphoma. The pathological and clinical features of the 28 cases of peripheral T-cell lymphoma are presented in detail. Survival data indicated no significant difference between the low grade and high grade histological types. Three of the patients had previous or concomitant malignancies. The percentage of T-cell lymphomas associated with HTLV-1 infection in Singapore is low compared to those areas in which HTLV-1 is endemic.

Frequent expression of haemopoietic and non-haemopoietic antigens by neoplastic plasma cells: an immunohistochemical study using formalin-fixed, paraffin-embedded tissue

There is increasing evidence that neoplastic plasma cells express various haemopoietic and non-haemopoietic antigens. Since this issue could raise problems in diagnostic histopathology, we have investigated 51 cases of multiple myeloma (plasmacytoma) systematically with a broad panel of antibodies applicable on paraffin-embedded and mildly decalcified tissue. In approximately 90% of the cases the neoplastic plasma cells reacted with at least one antibody detecting haemopoietic antigens: MB2 (75%), DF-T1/CD 43 (59%), UCHL1/CD 45RO (47%), Ki-B3 (41%), anti-LCA/CD 45 (40%), L26/CD 20 (26%), 4KB5/CD 45RA (18%), Ber H2/CD 30 (10%), anti-neutrophil elastase (4%), anti-Leu-7/CD 57 (8%), Dako-M1/CD 15 (2%), KP1/CD 68 (2%) and anti-glycoprotein IIIa (2%). In approximately 70% of the cases the cells reacted with antibodies against non-haemopoietic antigens: anti-epithelial membrane antigen (65%), BMA120 (53%), anti-vimentin (44%), anti-pan-cytokeratin/KL1 (8%), anti-carcino-embryonic antigen (6%) and HMB45 (6%). Lack of awareness of the frequent expression of both haemopoietic and non-haemopoietic antigens by neoplastic plasma cells could lead to mis-diagnosis of plasmacytomas as malignant lymphomas or even as carcinomas or sarcomas.

Immunohistochemistry on needle biopsies of childhood malignancies

Ultrasound-guided percutaneous needle biopsy proved to be a reliable and safe method to obtain material for histopathological and immunohistochemical diagnosis prior to treatment in childhood malignancies. A principal tumour identification could be obtained by a combined morphological and phenotypic examination of 38 small-sized tumour biopsy specimens using a fairly limited panel of immunological reagents, including antibodies to leucocyte common antigen (CD 45), certain B- and T-cell markers, various intermediate filaments (cytokeratin, desmin and vimentin), and neuroblastoma cells (UJ 167.11, A2B5, and UJ 13A; the latter recognizes NCAM). Five undifferentiated neuroblastomas were all positive with the neuroblastoma antibodies but negative for the other markers, including vimentin. The negative reactivity for desmin and vimentin was the major immunohistochemical distinction between neuroblastomas and rhabdomyosarcomas. In addition, limited reactivity with the neuroblastoma antibodies was seen in blastematous parts of Wilms' tumour, duct-like structures in a hepatoblastoma, and in tumour cells in a few undifferentiated myelo- and lympho-proliferative lesions. This study shows the importance of a combined evaluation of morphology and the pattern of immunoreactivity employing multiple markers.

Extranodal oral lymphomas: histologic subtypes and immunophenotypes (in routinely processed tissue)

Twenty-seven extranodal oral lymphomas were subclassified according to the National Institutes of Health International Working Formulation. Immunophenotypes were then determined by means of an ABC technique with newly generated antibodies that identify fixation-resistant antigens on lymphoid cells. Diffuse small and large cell lymphomas were the most frequently identified subtypes. B-cell-associated antibody, L26, stained a majority of tumor cells in all lymphomas. Although 4KB5 was a less consistent B-cell marker, it stained most lymphomas. Reactive T-cell infiltrates, identified with antibodies MT1, UCHL-1, anti-CD3, and OPD4, varied from slight to intense. MT1 occasionally showed cross-reactivity with neoplastic B cells. No "histiocytic" lymphomas were found, but reactive macrophage infiltrates were identified in many lymphomas with monoclonal antibody KP1. In view of the immunohistochemical results, all lymphomas were believed to be of B-cell origin. Although antibody panels of the type used in this study can be effective in subtyping routinely processed oral lymphomas, careful interpretation is required because of reactive T-cell infiltrates.

Phenotyping of T-cell lymphomas in paraffin sections--which antibodies?

Five antibodies, MT1 (CD43), UCHL1 (CD45RO), OPD4, poly-CD3 and beta F1, were assessed for their reactivity with 50 archival cases of T-cell lymphoma in formalin-fixed paraffin-embedded tissue. All cases had been previously characterized as T-cell lymphomas, and the histological types included 14 cases of small cerebriform lymphoma, six cases of angioimmunoblastic lymphadenopathy-like T-cell lymphoma, four cases of T-zone lymphoma, five cases of pleomorphic small cell lymphoma, 12 cases of pleomorphic medium and large cell lymphoma, four cases of anaplastic large cell lymphoma, two cases of T-lymphoblastic lymphoma and three cases of enteropathy-associated T-cell lymphoma. UCHL1 and MT1 showed reactivity with the highest percentage of cases (94 and 86% respectively) but lack absolute specificity for T-cells, especially in high-grade lymphomas. Poly-CD3 is highly specific for T-cells, and stained neoplastic cells in almost 80% of the cases. beta F1 stained the lowest percentage of cases (40%). UCHL1 and poly-CD3 together identified 98% of cases, and this combination is recommended for the diagnosis of T-cell lymphomas in paraffin sections.

Immunohistochemical evaluation of bone marrow lymphoid nodules in chronic myeloproliferative disorders

One hundred and seventy bone marrow biopsies from patients with chronic myeloproliferative disorders (CMPDs) were evaluated for the presence of lymphoid nodules (LNs) and were immunostained using a panel of monoclonal antibodies (UCHL1, 4KB5 and L26) recognizing different lymphocyte antigens. LNs were found in 35% of cases of idiopathic thrombocythaemia, 24.6% of myelofibrosis/osteomyelosclerosis, 18.2% of polycythaemia vera 12.1% of chronic myeloid leukaemia and 19.2% of borderline cases. Varying degrees of immunohistochemical positivity for the three antibodies tested were found. LNs were always made up of variable proportions of both T- and B-lymphocytes with a prevalence of T-cells. This latter observation suggests that bone marrow LNs in CMPDs could be an expression of reactivity.

Use of monoclonal antibodies for the typing of malignant lymphomas in routinely processed biopsy samples

Eight antibodies (UCHL1 (CD45RO), MT1 (CD43), MT2 (CD45R), 4KB5 (CD45R), MB1 (CD45R), MB2, L26 (CD20) and LN1 (CDw75)) have been examined for reactivity with routine specimens of normal and hyperplastic lymphoid organs (n = 6), non-Hodgkin's lymphomas (n = 62), Hodgkin's disease (n = 27) and non-lymphoid malignancies (n = 9). In normal and hyperplastic lymphoid organs, UCHL1 and MT1 stained predominantly T cells; 4KB5, MB1, MB2, L26 and LN1 stained predominantly B cells; and MT2 reacted with a subset of B and T cells. The lineage of the neoplastic cells was correctly identified in 24 of 28 (86%) peripheral T-cell lymphomas; and in 31 of 35 (88%) B-cell malignancies. In two cases of lymphocyte-predominant Hodgkin's disease, the Hodgkin's and Reed-Sternberg (H&RS) cells were 4KB5+, L26+ and/or LN1+. The H&Rs cells in nodular sclerosis and mixed cellularity Hodgkin's disease were positive with 4KB5 in 17 of 25 cases. Antibodies UCHL1, MT1, MB1, MB2, L26 and LN1 also labelled some H&RS cells, but in a much smaller proportion of the cases. In three of nine non-lymphoid neoplasms, UCHL1 and MB2 showed a staining of the neoplastic cells, but the staining was cytoplasmic rather than membrane-associated. The remaining antibodies were unreactive with the non-lymphoid malignancies. It is concluded that many non-Hodgkin's lymphomas can be typed in routine specimens, and that antibodies UCHL1, MT1, L26 and LN1 are especially useful in this respect. The antibodies do not provide a means of distinguishing between non-Hodgkin's lymphomas and Hodgkin's disease.

Non-Hodgkin's lymphoma involving the tonsil: an immunohistochemical study

Twenty-one patients with non-Hodgkin's lymphoma involving the palatine tonsil were studied in an attempt to relate pathological data to clinical outcome. Eleven tumours were classified as low-grade and ten as high-grade on morphological criteria. The results of immunohistochemical investigations are presented; all tumours but one were of B-cell origin. None of the pathological factors studied were found to be useful prognostic indicators.

Long-term survival in Ki-1 lymphoma

Three patients with histologic and immunologic features of Ki-1-positive large cell lymphoma, who experienced long-term survival, are presented. These three patients at 2, 28, and 49 years of age had adenopathy; all cases had been initially misdiagnosed as metastatic carcinoma or malignant histiocytosis. On subsequent review, they had sinusal and diffuse growth of large pleomorphic cells that were Ber-H2 (Ki-1; CD 30) positive. One case marked as a T-cell lymphoma with UCHL1, one case expressed T-cell and B-cell markers, and one case was negative for both T-cell and B-cell markers. All patients received chemotherapy, and two received local radiation. One patient was not treated until 9 years after initial diagnosis. Two patients had several recurrences, but there has been no evidence of lymphoma in any of the three patients for 63 to 301 months; overall survival time has ranged from 14 to 25 years. These cases are the longest reported survivors with Ki-1 lymphoma; 5 years was the longest survival time previously reported. It also is noteworthy that Ber-H2 and other lymphoid-associated antigens appear to be preserved in formalin-fixed, paraffin-embedded tissues for prolonged periods. This may allow retrospective studies to evaluate the natural history of Ki-1 lymphomas, as well as their spontaneous or treatment-induced regression.

CD30 expression in follicular lymphoma

The CD30 antigen is a characteristic phenotypic feature of Sternberg-Reed and Hodgkin cells and is also found in a subset of large cell non-Hodgkin's lymphomas. The finding of CD30 positive cells in some centroblastic/centrocytic (cb/cc) follicular lymphomas prompted us to characterize the presence and distribution of CD30 positive cells in this type of lymphoma, using the monoclonal antibody BerH2. CD30 positive cells were present in 17/19 of the cases studied, located mainly at the edge of the neoplastic follicles, but also in some cases in perinodular or T-cell areas. This distribution resembles that found in reactive tonsils and lymph nodes. The majority of these CD30 positive cells in cb/cc lymphoma seem to be B-cells, as suggested by their reactivity with B-cell markers demonstrated by double immunostaining. The nature of these CD30 positive cells is unclear, but they should be taken into consideration in the differential diagnosis of cb/cc lymphoma with lymphocyte predominance Hodgkin's disease.

Primary malignant lymphomas of the spleen. A morphologic and immunohistochemical analysis of 17 cases

Seventeen cases of primary malignant lymphoma of the spleen (PMLS) were identified among 500 splenectomy specimens showing involvement by Hodgkin's disease or non-Hodgkin's lymphoma. All PMLS represented non-Hodgkin's lymphoma and most of them were of B-cell origin. In two cases PMLS were associated with hamartomas of the spleen (splenomas). Histologic and immunohistochemical studies did not reveal any differences between PMLS and disseminated malignant lymphomas with splenic involvement with regard to morphologic features, immunophenotype, host cell infiltrates, or proliferation activity. The reasons for the infrequent occurrence of primary lymphomas in the spleen may not be sought in a special immunophenotype of PMLS, a vigorous host response in the spleen, or in a lower proliferation activity of splenic lymphomas.

Angiocentric immunoproliferative lesion/T-cell non-Hodgkin's lymphoma and the acquired immune deficiency syndrome: a case report and review of the literature

The lesions known as lymphocytic vasculitis, polymorphic reticulosis (midline malignant reticulosis, lethal midline granuloma), lymphomatoid granulomatosis, and angiocentric lymphoma form what have been collectively termed the angiocentric immunoproliferative lesions (AIL). Because of recent reports demonstrating clonal rearrangements of the T-cell receptor in these lesions, the AIL are now thought to represent a continuous spectrum of post-thymic T-cell non-Hodgkin's lymphoma (NHL). NHL associated with the acquired immune deficiency syndrome (AIDS) represents intermediate or high-grade B-cell malignancies in HIV-infected patients that may be etiologically related to the Epstein-Barr virus (EBV). There have been reports of EBV-associated T-cell NHL, AIL, and large granular lymphocyte (LGL) proliferations, as well as HIV-associated T-cell neoplasia, LGL/T-cell proliferations, and AIL. We describe a case of polymorphic reticulosis (lethal midline granuloma) arising in an HIV-infected individual, who later progressed to AIDS, and review the literature on HIV-associated and EBV-associated T-cell neoplasia, LGL/T-cell proliferations, and AIL. The etiology of this AIL/T-cell NHL, especially in relation to EBV and HIV, is discussed.

Primary lymphoma of the liver: clinical and pathological features of 10 patients

Nine out of 10 patients with primary lymphoma of the liver presented in a manner that did not suggest a tumour. The initial diagnoses were chronic active hepatitis in three cases and "granulomatous cholangitis", inflammatory pseudotumour, and anaplastic carcinoma in one case each. Moreover, extensive haemorrhagic necrosis in three cases initially suggested the Budd-Chiari syndrome. All the tumours were diffuse non-Hodgkin's lymphomas like the 50 cases reported previously, but they differed from most of these in that nine were of T cell phenotype. Five were pleomorphic small T cell, two T zone, and two T lymphoblastic lymphomas: only one was centrocytic and of B cell lineage. This report extends the range of clinical manifestations (diffuse hepatomegaly without a tumour), histological appearances (resemblance to chronic inflammatory or vascular liver diseases) and phenotype (of T cell lineage) of primary lymphoma of the liver: these features seemed to be related in this series. Recognition is important as prognosis remains favourable in appropriately treated cases. Although the appearances of the liver biopsy specimens may be difficult to interpret, the destructiveness of the infiltrate is an important clue to the diagnosis.

Peripheral T-cell lymphomas: a clinicopathologic study of 75 cases

Seventy-five peripheral T-cell lymphomas (PTLs) were classified according to the recently proposed "Updated Kiel Classification of Non-Hodgkin's Lymphomas" (mycosis fungoides and Sezary's syndrome excluded). Thirty-seven PTLs belonged to the low-grade category (T-cell chronic lymphocytic leukemia [T-CLL], 3; lymphoepithelioid, 4; angioimmunoblastic, 22; T-zone, 6; pleomorphic small cell, 2) and 38 belonged to the high-grade category (pleomorphic medium and large cell, 24; immunoblastic, 1; large-cell anaplastic Ki-1-positive, 13). Loss of pan-T antigens occurred exclusively in high-grade PTLs; on paraffin sections UCHL 1 was slightly more sensitive than MT 1. Sixty patients presented with lymphadenopathy and 15 patients (20%) presented with extranodal disease most frequently affecting the skin and upper aerodigestive tract. B-cell lymphoma symptoms were found in 43 cases (57%) and bone marrow involvement (T-CLL excluded) was found in 12 cases (17%). Staging (T-CLL excluded) revealed stage I in 13%, stage II in 15%, and stages III and IV in 72% of the cases. Among the intensively treated patients, 37% achieved complete remission and 15 are still in complete remission after 4 to 79 months (median: 24 months). The overall median survival (MS) rate was 23 months. Peripheral T-cell lymphoma of pleomorphic medium and large-cell type was the most aggressive lymphoma (MS: 8 months). B-cell lymphoma symptoms, bone marrow involvement, and Ki-67 positivity 60% or greater significantly shortened survival times, whereas age (under 60 versus over 60 years), stage (I and II versus III and IV), and grade had no significant influence. Ki-67 reactivity was found to be a prognostic factor which allows prediction of probable poor outcome, especially in cases with limited stage of disease.

Reticulin fibre content of bone marrow infiltrates of malignant non-Hodgkin's lymphomas (B-cell type, low malignancy)--a morphometric evaluation before and after therapy

A morphometric study was performed on bone marrow infiltrates of non-Hodgkin's lymphomas (B-cell type, low malignancy) to evaluate the content of argyrophilic (reticulin) fibres in the various subtypes before and after therapy. In congruence with the corresponding lymph node lesions, subtypes consisted of lymphocytic lymphoma--chronic lymphocytic leukaemia (CLL, n = 39), centroblastic-centrocytic lymphoma (CB-CC, n = 35), lymphoplasmacytoid immunocytoma (LPI, n = 22) and finally hairy cell leukaemia (HCL, n = 21). In comparison with control specimens, morphometric measurements on trephine biopsies (initial staging procedure) disclosed a borderline or minimal increase in reticulin in CLL and moderate fibrosis in CB-CC and LPI, whereas HCL had the greatest increase in fibres. The marrow surrounding focal or patchy lymphoma infiltrates of CLL and CB-CC displayed no relevant changes in fibre density with respect to the control samples. Following chemotherapy, repeated trephine biopsies (restaging procedure) were obtainable from 38 patients. There was no significant decrease in the fibre content of CLL, CB-CC and LPI infiltrates. In HCL an incomplete reduction was recorded after interferon treatment. So-called benign lymphoid lesions may be distinguished from focal-patchy infiltrates of CB-CC and LPI not only by showing a central localization, but also by the absence of significant amounts of reticulin. However, considering the density of the reticulin fibres, a clear-cut discrimination of these lymphoid aggregates from an early nodal-central growth pattern of CLL is not feasible in many cases.

Stereotactic biopsy diagnosis of primary non-Hodgkin's lymphoma of the central nervous system. A histological and immunohistochemical study

We report 29 cases of primary non-Hodgkin lymphomas (NHL) of the Central Nervous System (CNS), 26 of which were diagnosed by stereotactic biopsy and 3 by autopsy. In seven cases the patients were affected by AIDS. Histological examination of this series revealed 15 cases of immunoblastic lymphoma, 12 cases of centroblastic lymphoma, 1 case of lymphoplasmacytic immunocytoma and 1 case of unclassified high grade lymphoma. By immunohistochemistry the B-cell origin of lymphoma cells was demonstrated in 28/29 cases. Eight cases were assigned to the B-cell lineage by demonstration of monotypic surface or cytoplasmic immunoglobulin or of the B-cell phenotype CD22+, CD2-, CD3-, CD5-. In twenty cases the B-cell nature of lymphoma was identified by positivity with two or more anti-B monoclonal antibodies (LN1LN2MB2) and negativity by the anti-T monoclonal antibody UCHL1. The histologically unclassified case was a peripheral T-NHL (CD1-, CD2+, CD3-, CD5+, CD22-). We conclude that histological and immunohistological evaluation of stereotactic biopsy specimens provides sufficient information for diagnosis and phenotypic characterization of primary NHL of the CNS. These lymphomas exhibit important predominance of high-grade malignancy histological types and are nearly always B-cell derived. In addition, we provide further evidence that the panel of monoclonal antibodies LN1, LN2, MB2, and UCHL1 is useful for immunophenotypic characterization of brain lymphomas when only paraffin embedded stereotactic biopsy tissue is available.

Immunohistochemical differential diagnosis of granulocytic sarcomas and malignant lymphomas on formalin-fixed material

A panel of monoclonal antibodies (anti-CD45 [common leukocyte antigen], Ki-B3, L26, MT1, UCHL1, anti-CD15 [X-hapten], anti-neutrophil granule protein elastase [NP57]), anti-lysozyme, and the naphthol-ASD-chloroacetate reaction were applied to two cases of granulocytic sarcoma (GS) for evaluation of their utility in differentiating GS from malignant lymphoma. Lysozyme and naphthol-ASD-chloroacetate esterase were found to be the most reliable markers for detection of the myeloid nature of the tumour cells. GS infiltrated solely the mucosa of the nasal cavity in one case, while in the other it involved both the nasal cavity and maxillary sinus with simultaneous eruptions on the skin of the trunk. In both cases, peripheral blood and bone marrow findings were inconspicuous at the time of diagnosis of GS.

Variable expression of leucocyte-common (CD45) antigen in CD30 (Ki1)-positive anaplastic large-cell lymphoma: implications for the differential diagnosis between lymphoid and nonlymphoid malignancies

Monoclonal antibodies (mAbs) directed against the leucocyte common (CD45) antigen have been proposed as a useful tool for the differential diagnosis between malignant lymphomas (CD45+) and poorly differentiated nonhemopoietic tumors (CD45-). Thanks to the availability of mAbs directed against fixative-resistant epitopes of the CD45 molecule, this distinction can now easily be made even in routinely processed tissues. However, a small percentage of morphologically poorly defined neoplasms are difficult to diagnose even with the help of immunohistochemistry. The investigators report that 63 out of 165 anaplastic large-cell (ALC) lymphomas did not show any reactivity for the CD45 antigen in paraffin sections. In routine biopsies, the lymphomatous nature of these cases, most of which had been sent for consultation, could be always unequivocally established by demonstrating negativity for cytokeratins (mAb KL1) and clear dot-like and/or surface reactivity with the Ber-H2 mAb, which is directed against a fixative-resistant epitope of the lymphoid cell activation antigen CD30. Strikingly, 54% of the CD45-cases reacted with mAbs directed against fixative-resistant epitopes of the T cell-restricted CD45RO antigen (mAb UCHL1) or the B-restricted molecules CD45RA (mAb 4KB5) and L26 (unclustered). In order to avoid confusion of ALC lymphomas with anaplastic nonlymphoid tumors, pathologists must be aware of the existence of CD30+/CD45- ALC lymphomas, as they can mimic the above-mentioned malignancies both morphologically (due to the sinusoidal growth pattern) and phenotypically (due to the expression of EMA). The investigators conclude that the combined use of mAbs directed against fixative-resistant epitopes of the CD30, CD45RO, CD45RA, and L26 antigens and cytokeratins is essential for the correct diagnosis and treatment of these equivocal cases.

Malignant lymphoma of the lower urinary tract. A clinicopathological study with review of the literature

The clinical and histopathological findings are reported in 3 primary malignant lymphomas of the lower urinary tract. Two arose in the bladders of a 70-year-old man and a 67-year-old woman. The first was histologically low grade and the patient remains free of disease after more than 7 years. The second was an intermediate grade neoplasm and the patient died after 39 months. The third tumour was found in the urethra of a 76-year-old woman and it appears to represent only the third primary malignant lymphoma described at this site. The bladder is an uncommon primary site of extranodal lymphoma. Most patients present with haematuria and cystoscopy shows 1 or more solid, round, tumour-like masses. Histological grade, particularly follicle formation, appears to have predictive value.

Diagnosis of primary cerebral lymphoma with particular reference to CT-guided stereotactic biopsy

In establishing the histological diagnosis of primary cerebral lymphoma, stereotactic brain tumour biopsy is the method of choice as the mainstay of therapy is radiation and chemotherapy. This study describes the histopathology and diagnostic immunohistochemistry of 54 primary brain lymphomas in a mainly non-AIDS population. The stereotactic biopsies were performed using the Leksell CT stereotactic frame and a spiral needle which procured about 10-mm-long tissue cylinders. Usually, three successive biopsy cylinders were taken along the target trajectory. Histological examination revealed the prevalence of high-grade non-Hodgkin's lymphoma of the polymorphous centroblastic type. The series did not include any low-grade lymphomas or T-cell lymphomas. L-26 immunohistochemistry resulted in a positive staining of the blasts, thus confirming the B-cell origin of primary brain lymphomas. Small reactive T-lymphocytes and monohistiocytic cells were also found within and at the periphery of the lymphomas and in areas of degeneration. In the biopsies of nine patients, who had shown significant reduction of the lesions on the CT scans, after corticosteroid medication, regressive tissue changes were predominant and consisted of T-lymphocytes, macrophages, and occasionally bizarre reactive astrocytes.

B cell associated monoclonal antibody L26 may occasionally label T cell lymphomas

Monoclonal antibody L26 has been shown to be a very sensitive marker for B lymphocytes in formalin-fixed, paraffin-embedded tissue. Most studies have found that the antibody is also highly specific for B cells, although a few examples of L26-positive T cell lymphoma (TCL) have been reported. We have studied L26 reactivity in 50 TCLs (all previously extensively immunophenotyped on frozen sections) and found positive labelling in 4 cases (3 pleomorphic, medium and large cell type with surface membrane staining; 1 T-anaplastic large cell type with cytoplasmic staining). The finding that L26 may give surface labelling in occasional TCLs (particularly of the pleomorphic, medium and large cell type) indistinguishable from that seen in B cell lymphomas emphasises the importance of always using diagnostic MAbs in combination if the risk of misinterpretation of lymphoma cell lineage is to be minimised.

Diagnosis of T-cell lymphoma using beta F1, anti-T-cell receptor beta chain antibody

The reactivity of a new monoclonal antibody to the T-cell beta chain antigen receptor (beta F1) with routinely processed paraffin sections from patients with T-cell lymphoma is described. Staining of tumour cells was seen in 36/47 cases of T-cell lymphoma. No staining was seen in any cases of B-cell lymphoma (0/21 cases), nine of which had previously been shown to react with other T-cell antibodies (MT1/UCHL1). We conclude that beta F1 is a specific marker for demonstrating a T-cell histogenesis of lymphoma and with advantages over other currently available antibodies reactive with paraffin sections.

Immunophenotypic analysis of sinonasal non-Hodgkin's lymphomas

A panel of paraffin effective antibodies recognizing B cells and T cells (LN-2, MB1, L26, MT1, UCHL1, kappa, lambda) was used to characterize the immunophenotypes of 26 sinonasal non-Hodgkin's lymphomas. Seventeen tumors were stage I, five were stage II, one was stage III, and three were stage IV. Nine lymphomas were classified morphologically as large cell, six were large cell immunoblastic, six were small cleaved cell, two were mixed small and large cell, two were small noncleaved cell, and one was lymphoblastic. None were follicular. Twenty-two lymphomas had a B cell immunophenotype, three were T cell neoplasms, and one was immunoreactive only for MT1. This predominance of sinonasal lymphomas with a B cell immunophenotype in patients residing in the United States contrasts with the almost exclusive occurrence of T cell sinonasal lymphomas in Chinese patients living in Hong Kong and Japanese patients residing in regions of Japan that are nonendemic for human T cell leukemia virus-1.

Lymphoma phenotyping in formalin-fixed and paraffin wax-embedded tissues: II. Profiles of reactivity in the various tumour types

Recently, monoclonal antibodies capable of phenotyping malignant lymphomas in routinely fixed and processed tissue have become available. Some of these reagents identify lineage-restricted variants of the leucocyte common molecule, whereas others identify unique fixation-resistant epitopes on lymphoid cells, some of which are shared by non-lymphoid tissues. A new generation of antibodies recognizing 'classical' leucocyte antigens such as CD3 are also emerging. Refinements in antigen detection systems, especially for immunoglobulin recognition, combined with these new reagents promise to improve the accuracy of lymphoma diagnosis in routine histopathology. These new antibodies are reviewed, and their limitations, cross reactivities and profiles of staining in lymphoreticular disease are discussed. A strategy for their optimal use is proposed.

Extensive necrosis in malignant lymphoma with granulomatous reaction mimicking tuberculosis

Epithelioid cell granulomas occur in association with a wide range of neoplasms but necrotizing granulomas mimicking tuberculosis are less well recognized. Two cases of high-grade malignant lymphoma of Burkitt type are presented which were associated with such a response. In both cases this caused difficulty in interpretation and in one led to delayed diagnosis. Regional lymph nodes were not involved by lymphoma but contained epithelioid cell granulomas in both cases. Features that suggested that the granulomatous reaction was related to the tumour included a close spatial relation, the reticulin pattern in the areas of necrosis and the immunohistochemical demonstration of lymphoid antigens in the necrotic debris. A diligent search for mycobacteria and other micro-organisms failed to reveal any infective cause. We suggest that the local granulomatous response is a reaction to the presence of necrotic and poorly viable tumour and the granulomas in nearby lymph nodes may be a response to tumour derived debris.

Paraffin section immunohistochemistry. II. Hodgkin's disease and large cell anaplastic (Ki1) lymphoma

A panel of antibodies that recognize antigens that survive fixation and conventional processing have been applied to 43 cases of Hodgkin's disease and five cases of large cell anaplastic lymphoma. Reed-Sternberg cells in all five cases of nodular lymphocyte predominance Hodgkin's disease were positive with leucocyte common (CD45) and B-cell antibodies, and negative with LeuM1 (CD15) and BerH2 (CD30) antibodies. In other types of Hodgkin's disease, Reed-Sternberg cells were positive with BerH2 in all cases, positive with LeuM1 in 63% of cases (with enzymic predigestion), positive with at least one B-cell antibody in 29% of cases and positive for CD45 in 8% of cases. In 19% of all cases, Reed-Sternberg cells were positive for epithelial membrane antigen and in 93% they were positive with TAL1B5 (anti-class II MHC). No case showed immunoreactivity with anti-T-cell antibodies. The patterns of immunoreactivity of large cell anaplastic lymphoma were similar, except that none was positive with B-cell antibodies and three were positive with T-cell antibodies. All five were positive with BerH2 (CD30) and TAL1B5. Comparison of the results with those seen in other cases of non-Hodgkin's lymphoma indicates that, with the currently available reagents, this immunohistological profile cannot be used as the sole diagnostic discriminant of these conditions; this must still be based upon careful morphological assessment.