Small cell carcinoma of the cervix in liquid-based Pap test: utilization of split-sample immunocytochemical and molecular analysis.

Small cell (neuroendocrine) carcinoma of the uterine cervix (SMCC) is a rare, highly aggressive malignant neoplasm. Both conventional and liquid-based cytology (LBC) cervical smears have low sensitivity in diagnosing SMCC, requiring immunocytochemical (ICH) confirmation. We present the first series of SMCC primarily diagnosed in cytology specimens, and ICH studies performed on the residual LBC specimens with subsequent confirmation of the diagnosis on surgical pathology specimens. Immunocytochemical stains for keratin, p16INK4, and neuroendocrine markers (synaptophysin, chromogranin, CD56) were performed on additional ThinPrep slides. HPV test used chromogenic in situ hybridization high risk HPV DNA probe. The Pap smears in all three specimens were highly cellular with a mixture of squamous cells and numerous well-preserved single or small cohesive clusters of malignant epithelial cells. Tumor cells were small, monomorphic with minimal cytoplasm and high nuclear/cytoplasmic ratio. There was significant nuclear overlap, but no nuclear molding, or smudging of nuclear chromatin. The chromatin pattern was stippled. A background tumor diathesis was prominent. Atypical squamous cells of undetermined significance (ASCUS) were noted in one case, and markedly abnormal squamous cells were seen in another case. The main cytology differential diagnoses included high-grade squamous intraepithelial lesion and an endometrial adenocarcinoma. Immunocytochemical positivity for the neuroendocrine markers supported the diagnoses of SMCC in all three cases. The morphologic features of the concurrent surgical pathology specimens were typical of SMCC. The tissue diagnoses were also confirmed by immunohistochemistry. Our study allows us to conclude that SMCC can be primarily diagnosed in LBC specimens using a panel of immunocytochemical stains.

Sarcomatoid mesothelioma and its histological mimics: a comparative immunohistochemical study.

AIMS: Differentiating sarcomatoid mesothelioma from other pleural-based spindle cell tumours by light microscopy can be challenging, especially in a biopsy. The role of immunohistochemistry in this differential diagnosis is not as well defined as it is for distinguishing epithelioid mesothelioma from adenocarcinoma. In this study, we investigate the utility of diagnostic immunohistochemistry for distinguishing sarcomatoid mesothelioma from its histological mimics, high-grade sarcoma and pulmonary sarcomatoid carcinoma. METHODS: We stained 20 mesotheliomas with sarcomatoid components (10 biphasic and 10 sarcomatoid mesotheliomas) for pan-cytokeratin, cytokeratin 5/6, calretinin, WT-1, thrombomodulin, and smooth muscle actin. Intensity and distribution of staining were assessed using a semiquantitative scale. Only tumours with unequivocal staining were considered positive for tabulation. We compared the immunophenotypic profiles of these tumours with 24 high-grade sarcomas, 10 pulmonary sarcomatoid carcinomas, and 16 epithelioid mesotheliomas. The sarcomatoid carcinomas were also stained for thyroid transcription factor-1 (TTF-1). RESULTS: Pan-cytokeratin stained 70% of sarcomatoid mesotheliomas, 17% of sarcomas, 90% of sarcomatoid carcinomas, and 100% of epithelioid mesotheliomas. Cytokeratin 5/6 and WT-1 stained most epithelioid mesotheliomas, but rarely stained sarcomas, sarcomatoid carcinomas, or the sarcomatoid components of mesothelioma. Calretinin and thrombomodulin each stained 70% of sarcomatoid mesotheliomas. However, calretinin was also positive in 17% of sarcomas and in 60% of sarcomatoid carcinomas, while thrombomodulin was positive in 38% of sarcomas and in 40% of sarcomatoid carcinomas. Smooth muscle actin was expressed in 60% of sarcomatoid mesotheliomas and in 58% of sarcomas, but in only 10% of sarcomatoid carcinomas. All 10 sarcomatoid carcinomas were negative for TTF-1. CONCLUSIONS: Mesothelioma shows decreased expression of epithelial and mesothelial epitopes in its sarcomatoid components. A wide immunophenotypic overlap exists among sarcomatoid mesotheliomas, sarcoma, and sarcomatoid carcinomas. Cytokeratin and calretinin have the most value in differentiating sarcomatoid mesothelioma from sarcoma. However, because sarcomatoid mesothelioma can occasionally be cytokeratin-negative, the distinction between it and sarcoma may become arbitrary. With the exception of smooth muscle actin, all the markers studied showed similar distributions in sarcomatoid mesothelioma and sarcomatoid carcinoma, including frequent calretinin and thrombomodulin expression in both tumours. Thus, immunohistochemistry plays a more limited role in the differential diagnosis of sarcomatoid tumours compared with epithelioid tumours. For sarcomatoid tumours involving the pleural lining, clinicopathological data, especially information about the gross appearance of the tumour (i.e. localized versus diffuse pleural-based mass), should be noted and carefully correlated with microscopic and immunohistochemical findings.

Ewing sarcoma vs lymphoblastic lymphoma. A comparative immunohistochemical study.

To develop a practical immunohistochemistry panel for distinguishing lymphoblastic lymphoma from Ewing sarcoma (ES), we evaluated 17 ES and 27 lymphoblastic lymphoma and leukemia cases with antibodies to CD99, terminal deoxynucleotidyl transferase (TdT), leukocyte common antigen (LCA), CD43, CD79a, CD20, CD3, vimentin, and neuron-specific enolase (NSE). Three cases were bone lymphomas, 2 initially misdiagnosed as ES. All cases were CD99+. All lymphomas and leukemias were TdT+ compared to none of the ESs. None of the ESs expressed other lymphocytic markers, which were inconsistently expressed in the lymphomas and leukemias: CD43, 33%; LCA, 30%; CD79a, 19%; CD3, 19%; and CD20, 7%. Of the ESs, 88% were vimentin positive compared with 23% of lymphomas and leukemias. Vimentin was stronger and more diffuse in ES. NSE did not reliably stain any cases. When faced with the differential diagnosis of ES vs lymphoblastic lymphoma, an immunohistochemical panel that includes antibodies to CD99 and TdT is useful. Both epitopes are well preserved in fixed and decalcified tissue. A panel composed of antibodies to CD99 and TdT, in conjunction with other lymphocytic markers and vimentin, is highly sensitive and specific.

Value of Ki67 immunostain in identification of malignancy in serous effusions.

The distinction between malignant and benign serous effusions continues to be a challenging and a frequent problem to cytopathologists. Recently, immunostains employing various antibodies have improved the diagnostic accuracy of malignant effusions. We investigated the usefulness of Ki67 (MIB1) antigen immunostaining in the evaluation and diagnosis of malignant serous effusions. Cell block sections from a total of 54 cases of serous effusions cytologically diagnosed as malignant (28), suspicious (6), and benign (20) were immunostained with MIB1 monoclonal antibody to the Ki67 nuclear proliferation antigen according to the avidin-biotin immunoperoxidase method. The patients were 30 women and 24 men with an average age of 58 yr. Ki67 (MIB1) immunostain labeling index (LI) values were higher than 20% in 23 of 28 (82%) cytologically malignant, in 3 of 6 (50%) suspicious, and in 1 of 20 (5%) benign/reactive. Further investigation revealed histologic, radiologic, and/or clinical evidence of malignancy in the 3 suspicious (but not in the benign/reactive) cases with Ki67 LI values higher than 20%. Correlation between Ki67 LI (> 20%) and cytologic effusion type (benign, suspicious, or malignant) was statistically significant (P < 0.0001). Ki67 immunostaining has value as an adjunct testing to cytomorphology and other immunostains in distinguishing benign from malignant effusions. The addition of Ki67 immunostaining to conventional cytology appears more sensitive than cytomorphology alone and may assist in arriving at accurate diagnoses in suspicious cases with inconclusive cytomorphologic features.

Improved detection of adenocarcinoma of serous fluids with p53 immunocytochemistry.

OBJECTIVE: To investigate the potential value of p53 protein immunostaining in identifying malignant cells in serous fluids. STUDY DESIGN: We applied p53 immunostaining to 26 cytologically malignant, 8 suspicious and 34 benign specimens of serous fluids from 68 patients. For comparison, staining for carcinoembryonic antigen (CEA) was also done on all the specimens. RESULTS: CEA was positive in 23 of 26 (88%) cytomorphologically malignant, 3 of 8 (38%) suspicious and 1 of 34 benign cases. p53 Nuclear immunostaining was positive in 12/26 (46%) malignant, 2/8 (26%) suspicious and no benign cases. Correlation between p53 staining and serous fluid type (benign, suspicious or malignant) was significant. The P based on Fisher's exact test was < .0001. Two cases that were reported cytomorphologically as suspicious stained positively with p53; further investigation in those cases confirmed the diagnosis of metastatic adenocarcinoma. CONCLUSION: p53 Immunostaining of serous fluids seems to be of value in identifying carcinoma cells, especially in those cases that show inconclusive or bland cytologic features. Combining p53 with CEA immunostains in clinically or cytologically suspicious cases may assist in recognition of carcinoma cells and in pursuing an appropriate therapeutic approach.

P53 protein immunohistochemical expression in colonic adenomas with and without associated carcinoma.

OBJECTIVES: P53 protein immunohistochemical (IHC) expression was investigated in a series of colonic adenomas and carcinomas to determine the p53 immunohistochemical expression of adenomas in general compared with carcinomas, the difference in staining pattern between adenomas with associated carcinoma and those without associated carcinoma, and the difference in p53 staining in the usual adenomas (low-grade dysplasia) compared with those harboring high-grade dysplasia. METHODS: The study involved a series of 20 adenomas without concurrent carcinoma (group 1 adenoma), 29 adenomas with concurrent carcinoma (group 2 adenoma), and 20 carcinomas. Sections of the paraffin-embedded tissues were stained with DO-7 p53 monoclonal antibody after microwave antigen-retrieval method. Cases with nuclear staining in > or = 20% of the tumor cells were considered positive. RESULTS: Analysis of results showed that 65% of carcinomas and 37% of all adenomas were reactive with p53 IHC staining (p = 0.03). With respect to the adenomas, 30% of group 1 and 41% of group 2 adenomas were reactive for p53 protein (p = 0.42). CONCLUSIONS: Our data demonstrate a statistically significant higher p53 expression rate in colonic carcinomas than in adenomas, and that adenomas with concurrent carcinomas are more frequently p53 positive than those without concurrent carcinoma, but this was not statistically significant. Also, p53 expression is more frequent and intense in adenomas with high-grade dysplasia (10/20, 50%) than in ordinary adenomas with low-grade dysplasia (8/29, 28%), which suggests a strong correlation between the degree of dysplasia in colonic neoplasia and p53 expression pattern.

Histopathologic and flow-cytometric analysis of neoplastic and benign "background" tissue in breast carcinoma resections.

Two-color, multiparametric synthesis phase fraction (SPF) analysis of cytokeratin-labeled epithelial cells was flow cytometrically performed on both benign (SPFb) and malignant tissue samples (if available, SPFt) from 132 mastectomy/lumpectomy specimens. These data were then correlated with clinicopathologic features, including (1) tumor differentiation, (2) the proportion of tumor comprised of duct carcinoma-in situ (DCIS), and (3) the histology of accompanying benign breast tissue, classified by predominant microscopic pattern as intact, normal terminal duct lobular units (NTDLU, 34% of cases), atrophic (AT, 33% of cases), proliferative fibrocystic (PFC, 26% of cases), and non-proliferative fibrocystic (NPFC, 7% of cases). SPFt was inversely correlated with extent of DCIS (DCIS = 0-20% tumor volume - 12.7% mean SPFt, vs. DCIS >20% tumor volume - 6.4% mean SPFt, p = 0.001). SPFt also correlated with the histology of background benign breast tissue (NTDLU - 14.8% mean SPFt vs. AT - 6.9% mean SPFt vs. PFC - 12.7% mean SPFt, p = 0.05) but it did not correlate with patient age or SPFb (overall mean = 0.73%). SPFb was correlated with patient age (>56 yr - 0.59% mean SPFb vs. <56 yr - 0.84% mean SPFb, p = 0.02), with background histology (NTDLU - 1.1% mean SPFb vs. AT - 0.43% mean SPFb vs. PFC - 0.70% mean SPFb, p < 0.02) and with the grade of the neoplasm (well/moderate - 0.58% mean vs. poorly differentiated - 0.85% mean, p = 0.04). Patients having a background of PFC were significantly older than patients with a background of NTDLU (45.2 yr vs. 60.2 yr, p = 0.01). We conclude: (1) breast carcinomas arising from a background of more actively cycling pre-involutional or proliferative fibrocystic epithelium have a greater proliferative fraction than tumors arising from atrophic epithelium, implying that the differentiation status of target cells may impact the effect(s) of tumorigenic events; (2) PFC may represent delayed, abnormal or interrupted involution rather than a hyperproliferative state relative to NTDLU, suggesting that it facilitates neoplasia by extending the period of exposure to promoter agents such as endogenous hormones, and (3) lower SPFt in breast neoplasia with more abundant "residual" DCIS may reflect a lengthier pre-invasive disease interval due to intrinsically less aggressive phenotype.

Clinicopathologic analysis of k-ras, p53, and ERBB-2 gene alterations in pulmonary adenocarcinoma.

We compared PCR-SSCP detected mutations of k-ras (codon 12) and p53 (exons 5-8) to ERBB-2 immunostaining and clinicopathologic features in 31 pulmonary adenocarcinomas. There were nine tumors (29%) with mutations of ras, 13 tumors (42%) with mutations of p53, and three tumors (10%) with mutations of both. Neither k-ras nor p53 mutation alone was significantly correlated with stage, grade, or survival. However, tumors with k-ras mutation were more frequently associated with an invasive growth pattern, defined as > 30% tumor volume composed of infiltrative nests of cells within desmoplastic, scar-like stroma [< 30% volume invasive--1/13 (8%) with k-ras mutation vs. > 30% volume invasive--8/18 (44%) with k-ras mutation, p = 0.02]. Accordingly, k-ras mutations were observed in only 1/9 (15%) predominantly bronchoalveolar or papillary tumors versus 6/22 (28%) acinar or scar carcinoma tumors. All three patients with combined k-ras/p53 mutation had advanced stage (III/IV) at presentation and died of the disease. In contrast to k-ras, staining for ERBB-2 was more frequently observed in tumors exhibiting < 30% invasive growth pattern (12/13, 92%) than in tumors with > 30% invasive growth pattern (10/18, 56%, p = 0.03). ERBB-2 immunoreactivity was more frequent in Stage I (14/15, 93%) versus Stage II-IV (8/16, 50%) cases, but it did not correlate with survival. There was a reciprocal relationship between k-ras mutation and ERBB-2 staining; only 4/9 (44%) k-ras mutated cases were ERBB-2 positive versus 18/22 (82%) cases without k-ras mutation (p = 0.005). In contrast, 8/13 cases with p53 mutation were ERBB-2 positive. We conclude that well-differentiated and less invasive papillary and bronchoalveolar tumors are more often ERBB-2 positive/k-ras negative (i.e. at codon 12), whereas less well differentiated acinar or scar carcinomas are more often ERBB-2 negative/k-ras mutated at codon 12. These findings imply that the divergent histogenesis of pulmonary adenocarcinoma may reflect specific differences in genetic pathology.

Cell cycle analysis of normal, atrophic, and hyperplastic breast epithelium using two-color multiparametric flow cytometry.

We performed two-color flow cytometric synthesis phase fraction (SPF) determinations on cytokeratin-labeled benign epithelial populations from 142 breast specimens (41 mastectomy, 70 diagnostic biopsy, 31 reduction mammoplasty). There was wide variability of SPF, ranging from 0.1 to 3.5%, with a frequency distribution skewed to higher values (mean 0.75%, median 0.5%). The mean SPE for women less than 29 years was 0.91%, vs. 0.89% for 30-42 years, 0.66% for 43-49 years, and 0.56% for > or = 50 years (P = 0.05). Histologically atrophic tissue samples exhibited a mean SPF approximately half that of morphologically normal tissue from premenopausal age women (0.79% vs. 0.36%, P = 0.02). Tissues showing histologically proliferative fibrocystic features had a greater mean SPF than non-proliferative fibrocystic tissues (0.59% vs. 0.92%); however, due to the wide spread of values within each of these categories, this difference was not statistically significant and neither group was significantly different from 'normal' tissue samples. Patients with histologically normal breast tissue, though, were significantly younger (mean = 34.6 years) than those with fibrocystic changes (non-proliferative mean = 53.4 years vs. proliferative mean = 42.8 years, P = 0.005). Synchronous right- and left-sided specimens obtained from reduction mammoplasty demonstrated significantly correlated SPF determinations (R = 0.77). We conclude that selective analysis of epithelial populations using two-color flow cytometry provides cell cycle information in benign breast tissue which is analogous to that obtained by labor-intensive nucleotide labeling studies. This study also confirms the biologic variability and age-dependence of breast epithelial proliferation. Finally, the data imply that derangements of cell proliferation in fibrocystic conditions are heterogeneous, complex and incompletely correlated with histologic parameters such as hyperplasia.

Clinicopathologic analysis of bcl-2 immunostaining in breast carcinoma.

Tissue sections of 81 breast carcinomas and 19 benign breast tissues were immunostained with a monoclonal antibody to the bcl-2 gene product, a cytoplasmic protein that regulates apoptosis. The degree of immunoreactivity was then compared with clinicopathologic parameters and to immunostaining for mutated p53 gene product. Immunoreactivity for bcl-2 was present consistently in lymphocyte populations and in residual benign lobules. Apocrine metaplasia (n = 6) and lactating breast (n = 1) exhibited minimal bcl-2 expression, whereas duct hyperplasia (n = 10) showed staining of cells primarily at the periphery of the involved structure and adenosis (n = 7) displayed staining in a majority of cells. Neoplastic epithelial bcl-2 immunoreactivity was negative or minimally positive (staining in 1-5% of cells) in 42% of cases, heterogeneous (staining in 6-30% of cells) in 27% of cases, and diffuse (> 30% of cells) in 31% of cases. Immunostaining for bcl-2 correlated with the presence of estrogen receptor (bcl-2 negative, 16% estrogen receptor positive versus bcl-2 positive, 88% estrogen receptor-positive; P < 0.001), with differentiation (bcl-2 negative, 62% poorly differentiated versus bcl-2 positive, 8% poorly differentiated; P < 0.001) and with better disease-free survival (bcl-2 negative, 82% recurrence versus bcl-2 positive, 28% recurrence; P = 0.0001; 52-mo mean follow-up). Immunostaining for p53 in greater than 5% of tumor cells was observed in 39% of cases and was more frequent in bcl-2-negative tumors (18/35, 51%) as opposed to bcl-2-positive tumors (14/46, 30%); P = NS. Disease recurrence correlated with p53 staining, which was observed in 51% of tumors that relapsed versus only 22% of tumors that did not recur. We conclude that bcl-2 is expressed in benign breast tissues that retain proliferative capacity and partial differentiation. Moreover, in neoplastic breast tissue, it is better correlated with a differentiated, "hormonally responsive," prognostically favorable phenotype than with disabled p53 gene function.

Clinicopathologic analysis of macrophage infiltrates in breast carcinoma.

We compared macrophage density, assessed by enumeration of peritumoral mononuclear cell immunoreactivity for HAM 56, to clinicopathologic features and to immunostaining for two "invasion-associated" proteases (Cathepsin D and Urokinase plasminogen activator) in 80 breast carcinomas. Diffuse (2+) infiltrates of HAM 56- positive mononuclear cells were present in 27 cases (34%) and 43 (54%) exhibited focal (1+) infiltrates. Presence of 2+ macrophage infiltrates correlated significantly with poor differentiation. None of the seven well-differentiated cases exhibited 2+ infiltrates, whereas 9/43 (21%) moderately differentiated and 18/30 (60%) poorly differentiated tumors were diffusely infiltrated (p = .001). Wide-spread macrophage infiltrates were also more frequent in cases with advanced stage (23% of node negative vs 40% of node positive cases, p = NS). Forty-four percent of the cases with diffuse macrophage infiltrates were cathepsin D positive (i.e. in host derived cells) vs only 18% with focal macrophage infiltrates (p = .002). A similar relationship was observed between staining for HAM 56 and urokinase-type plasminogen activator (p = .02). Disease recurrences (50 months median follow-up) were more frequent in patients with 2+ (17/27, 63%) as opposed to 0+ (1/10, 10%) macrophage infiltrates (p = .01). We conclude that the density of stromal macrophage infiltrates is associated with clinical aggressiveness in breast carcinomas. Further, this relationship may reflect contribution of host derived macrophages to invasion and metastasis through elaboration of proteases which putatively mediate degradation and remodeling of extracellular matrix.

A method for measuring lymphocyte proliferation in mixed lymphocyte cultures using a nuclear proliferation antigen, Ki-67, and flow cytometry.

The mixed lymphocyte culture procedure using tritiated thymidine (3H-TdR) incorporation is time consuming and labor intensive, therefore costly. With the use of a fluorescent antibody to a human nuclear proliferation antigen, Ki-67, and flow cytometry, mixed lymphocyte cultures on 20 families of renal and bone marrow transplant patients and normal controls were performed. In this method for measuring lymphocytic proliferation, previously developed by the authors, the entire culture and staining procedures are performed in microculture plates. Finally, the cell suspensions are aspirated with a microsampler to be analyzed by a flow cytometer. Excellent correlation of the percentage of Ki-67-positive cells and the counts per minute (CPM) of 3H-TdR incorporated into the DNA was obtained. This method eliminates the use of radioactive labels, is less time consuming, and yields results two to three days earlier than the radioactive method. In addition, the authors dual-labeled the lymphocyte nuclei with Ki-67 and propidium iodide (Ki-67/PI). This permitted the comparison of the appearance of nuclear antigen with the various phases of the cell cycle.

B lymphocytic lymphoma (large cell) of possible splenic marginal zone origin presenting with prominent splenomegaly and unusual cordal red pulp distribution.

Two cases of large cell lymphoma, B-cell type, primarily involving the red pulp of the spleen rather than the white pulp are described. A number of unusual features suggest that this may be a lymphoma originating from a distinct splenic B-cell lymphocyte whose origin may be the marginal zone of the spleen or the splenic cords. The patients presented with splenomegaly, cytopenias, and no peripheral lymphadenopathy. The gross appearance of the spleens was beefy red without tumor nodules. The tumor cells were primarily in the splenic cords and surrounding residual normal white pulp. There was a minimal hemic phase. The tumor cells had abundant cytoplasm, surface IgM, IgD, kappa, and FC receptors, tartrate-resistant acid phosphatase, but no alkaline phosphatase or interleukin-2 receptors. They had a similar DNA aneuploidy. The most unusual feature was that tumor cells in both cases had phagocytic properties. These lymphomas may be clinically more indolent than their follicular center counterparts.

A flow cytometric method for measuring lymphocyte proliferation directly from tissue culture plates using Ki-67 and propidium iodide.

A new method for measuring lymphocyte proliferation in response to mitogens and allogeneic cells without using radiolabelling is described. It utilizes flow cytometry and the monoclonal antibody, Ki-67, which detects a nuclear proliferation antigen. The entire test is performed in standard, 96-well tissue culture plates. Stable, clean nuclear suspensions rather than whole cells were used to avoid non-specific staining. The nuclei were stained by the indirect fluorescent method. Simultaneous measurements of DNA content were possible by dual staining with propidium iodide (PI). The percentage of Ki-67-positive nuclei correlated well with [3H]thymidine uptake and morphologic quantitation of blasts. This method avoids use of radioactive material and is less time consuming.

Storage and transportation of lymphoid tissue for immunophenotyping.

Immunoperoxidase staining of frozen sections is a cost-effective technic for immunophenotyping cells of lymphoid tissue. Because this procedure is not performed in many institutions, a simple method to transport fresh tissue to centers performing these studies is required. Tissues in saline at refrigerator temperature may be successfully transported. In addition, in order to minimize laboratory expenses, lymphoid tissue can be kept refrigerated in saline until permanent sections are examined and immunodiagnostic procedures become necessary. In this study reproducible immunophenotyping of 12 samples of lymphoid tissue stored up to seven days was achieved.

Comparison of morphologic features and mitotic rate to cytometrically determined DNA content of poorly differentiated lymphocytic lymphomas.

A direct correlation between the percentage of cells in S phase of the cell cycle and the clinical behavior of lymphocytic lymphomas of low, intermediate, and high grade malignancy has been described. The histopathologist has used the mitotic rate and other morphologic criteria such as size of cells and nuclear characteristics as predictors/indicators of the aggressiveness of a tumor. We compared the S phase values of 22 cases of poorly differentiated lymphocytic lymphoma (PDL) of the B cell type, using flow cytometric measurement of DNA content, to morphologic features and mitotic rate (MR). The 22 cases were divided into 3 histologic groups: nodular PDL composed of small, cleaved lymphocytes (11 cases); follicular mantle zone lymphoma and those of intermediate differentiation (6 cases); and "blastic" PDL (5 cases). In Group 1 there was excellent correlation of MR, percentage of cells in S phase, and proportion of large cells (transformed lymphocytes) per high power field (HPF). In Group 2, this correlation was not found between MR and percentage of cells in S phase in five of the six cases. The high S phase in this group did correlate with the large proportion of large cells found primarily in pseudofollicular proliferation centers and in remnants of true follicular centers. These cells may have a prolonged S phase and thus fewer mitoses were seen. In Group 3, although both MR and S phases were high, a direct correlation between them as noted in the Group 1 cases was not seen, but an excellent correlation of the high S phase and the number of blasts was present. The fact that three of the five patients in this group died rapidly (within less than 2 years of presentation) and the two survivors were experiencing rapid progression of disease, supports the concept that this group represents a clearly different, more aggressive subclass of PDL.

B-cell lymphomas morphologically resembling T-cell lymphomas.

Seven cases of B-cell lymphoma that morphologically resembled T-cell lymphoma are described. These cases are of four morphologic types: atypical poorly differentiated lymphocytic lymphoma (PDLL) with convoluted nuclei, "Lennert's" lymphoma, mixed lymphocytic-"histiocytic" lymphoma with large variation in size of abnormal cells, and "histiocytic" lymphoma with large multilobed nuclei. These cases add further support to the belief that morphologic criteria alone are not sufficient for accurate immunologic classification of the malignant lymphomas since they may represent a distinct clinicopathologic entity.

In vitro neutrophil-erythrocyte rosette formation mediated by a serum factor (IgG).

In vitro neutrophil-erythrocyte rosette (NER) formation occurred in the peripheral blood of an elderly man. This caused problems in cross-matching for blood transfusion initially but was resolved by performing crossmatches at 37 degrees C because this phenomenon was temperature-dependent. NER formation was independent of complement and of the type of anticoagulant used. NERs were induced using normal control cells with the patient's plasma, serum, and the IgG fraction of serum. The rosetting factor was adsorbed by heterologous group-specific erythrocytes, but not by leukocytes. No neutrophil antibodies were identified.

True histiocytic lymphoma. A report of four cases.

Clinical, morphologic, cytochemical, immunologic, and ultrastructural features of four cases of true histiocytic lymphoma are described. The neoplastic cells were large, ranging from 20 to 45 mu in diameter with round, folded, or convoluted nuclei, and abundant eosinophilic cytoplasm. They exhibited diffuse nonspecific esterase activity. Diffuse acid phosphatase activity was present in two cases so tested. Muramidase activity was present in half of the cases. Finely granular PAS-positive material was seen in the cytoplasm. Methyl green-pyronin positivity was variable. An occasional neoplastic cell showed erythropagocytosis in one case. Malignant cells either contained no cytoplasmic immunoglobulins (three cases) or had immunoglobulins of multiple classes (one case). Surface markers were studied in two cases; they were absent in one case, and were of multiple classes in another case. Ultrastructurally the neoplastic cells had lysosomal granules in three cases so examined, and phagolysosomes, phagocytized material and residual bodies in one of three cases so studied. Patients ranged in age from 28 to 60 years. Two patients had extralymphatic tumors. Survival of more than 5 years was seen in one patient.