Carcinoma masquerading as a pancreatic pseudocyst on ultrasound

Ultrasound has proven invaluable in detecting and evaluating pancreatic pseudocysts, and it is now a standard test to rule out complications of pancreatitis. In reviewing the authors' experience with 122 patients treated surgically for a pancreatic pseudocyst, five patients were identified in whom an ultrasound demonstrated a pseudocyst that was associated with an unexpected cancer at the time of operation. A sixth patient, with a pseudocyst documented by ultrasound, died prior to surgery and was found at autopsy to have metastatic common bile duct carcinoma. There was little difference in presenting symptoms, age, frequency of alcoholism, or physical findings compared with patients with pseudocysts secondary to pancreatitis. In two patients, pseudocysts were found in the tail of the pancreas at operation, in addition to carcinoma. In the other three patients, no pseudocyst was found; however, a subcapsular splenic hematoma was present in one. Five patients had metastatic disease, three from pancreatic adenocarcinoma, one from islet cell carcinoma, and one from a common bile duct carcinoma. One patient with a pancreatic adenocarcinoma confined to the head underwent a Whipple procedure and has no evidence of disease 6 months later. Malignancy may cause or coexist with pancreatic pseudocysts. Ultrasound is often not helpful in distinguishing pseudocysts associated with malignancy from those associated with pancreatitis. Biopsy should be performed to rule out malignancy when operating for pancreatic pseudocysts.

Genotypic and phenotypic evolution of a murine tumor during its progression in vivo toward metastasis

To follow the cellular progeny of the multiple-drug-marked benign murine tumor cell line MDW4 during its progression in vivo toward metastatic spread in DBA/2 mice, the following parameters were analyzed: retention of the drug-resistant markers ouabain resistance (OuaR) and thioguanine resistance (ThgR), lectin-resistance pattern (WGAR), and the karyotype of cell populations (and clones derived from these cells) removed at intervals from the solid tumor growing at the site of inoculation, as well as distant metastatic nodules. It was determined that the initially homogeneous inoculum composed of OuaR, ThgR, and WGAR hypotetraploid cells (mode: 68 +/- 2 chromosomes) was gradually overgrown and replaced by a new population of cells that were either OuaR or ouabain-sensitive but that became thioguanine-and lectin-sensitive and hyperploid (mode: 95 +/- 5). Regardless of the composition of the individual drug marker combinations, only cells with high chromosome contents were found to be able to disseminate to distant visceral organs and to rapidly produce metastases upon sc or iv reinjection. The presence of the same number of metacentric chromosomes in metastatic cells as in MDW4 and the coextinction of two recessive drug-resistant markers (WGAR and ThgR) suggested that cells endowed with invasive-metastatic potential represent the product of spontaneous somatic hybridization between the original nonmetastatic MDW4 cells and normal host cells of unknown origin. Such a fusion was followed by more or less extensive chromosome segregation that accounts for the karyotype mosaicism and the occasional drug marker heterogeneity identified in cell populations of metastatic nodules.

Spontaneous fusion in vivo between normal host and tumor cells: possible contribution to tumor progression and metastasis studied with a lectin-resistant mutant tumor

Previous studies demonstrated that growth in DBA/2 mice of MDW4, a wheat germ agglutinin-resistant (WGAr) mutant of the highly metastatic MDAY-D2 DBA/2 mouse tumor, led to the emergence of WGA-sensitive (WGAs) revertants having higher ploidy levels at the site of inoculation as well as at distant visceral metastases. The results implied that MDW4 was nonmetastatic but progressed to become metastatic in vivo only after a cellular change took place which was accompanied by extinction of the WGAr phenotype and acquisition of a higher number of chromosomes. Results presented here provide strong and direct evidence for the underlying mechanism being spontaneous cell fusion in vivo between the MDW4 (WGAr) tumor cells and normal host cells, at least some of which are of bone marrow origin. Thus, growth of the H-2d MDW4 tumor cells in (C3H X DBA/2)F1 (H-2k X H-2d) or (C57BL/6 X DBA/2)F1 (H-2b X H-2d) mice led to the appearance of WGAs revertants bearing the H-2k or H-2b major histocompatibility complex antigens associated with the C3H or C57BL/6 parental strains, respectively. Similarly, WGAs revertants of MDW4 were found to express H-2k antigens after growth in CBA/HT6T6 (H-2k) leads to DBA/2 bone marrow radiation chimeras. Attempts to mimic the in vivo hybridization process were successful in that in vitro somatic cell fusion between an ouabain-resistant (OuaR), 6-thioguanine-resistant (Thgr) derivative of the MDW4 mutant and either normal bone marrow or spleen cells resulted in loss of the WGAr phenotype in the hybrids (thus showing its recessive character) and increased malignant properties in vivo. An analysis of spontaneous frequencies of re-expression of various drug resistance genetic markers in several hybrid metastatic cells was also consistent with chromosome segregation of the sensitive alleles. The results show that tumor progression and the emergence of metastatic cell variants could arise as a consequence of tumor X host cell fusion followed by chromosome segregation. We also discuss the possibility that this type of event may normally be a very rare one during the growth of tumors, the frequency of which can be artificially amplified by the use of certain classes of lectin-resistant mutants carrying particular cell surface alterations.

Comparative analysis of cell surface markers on murine NK cells and CTL target-effector conjugates

The rosetting of sheep erythrocytes (SRBC) coated with non-haemagglutinating monoclonal antibodies rather than conventional haemagglutinating antisera revealed readily detectable FcR on most splenic natural killer (NK) cells since 76% of splenic lymphocytes forming conjugates with YAC also rosetted with SRBC coated with high concentrations of monoclonal anti-SRBC antibody of the IgG2b subclass and since Ficoll depletion or enrichment of splenic lymphocytes rosetting with IgG2b-coated SRBC resulted in a corresponding 4-fold decrease or increase in conjugate-forming cells and a 10-fold decrease or increase in NK cytolytic activity. NK cells bound much less readily to monoclonal IgG2a and not at all to monoclonal IgG1 or IgM, but the degree of binding was directly proportional to the amount of antibody on the erythrocytes and was not isotope-restricted. In addition, immunofluorescent studies revealed that YAC-1-conjugated lymphocytes were Lyt-1-, Lyt-2-, partially Thy-1+ (60%), asialo(GM1+ (80%). Qa-4+ (77%), Qa-5+ (79%), and Ly-5+ (94%). In comparison, a proportion (39%) of alloimmune peritoneal exudate cells which conjugated with P815-2 also stained by immunofluorescence with anti-asialo GM1 antisera. Most (greater than 90%) P815-conjugated cells were Thy-1+, Lyt-2%, and a subpopulation of Lyt-1+2+ conjugates was observed (25%). Qa-5 and Ly-5 were also expressed on most (two-thirds) cytolytic T lymphocytes (CTL) conjugates, whereas Qa-4 and FcR for IgG2b were not detected. The best phenotype distinctions between NK cells and CTL were therefore based on the presence or absence of Lyt-2, Qa-4, and FcR for IgG2b on most effector cells. Anti-asialo-GM1 or monoclonal anti-Qa-4 and complement treatment greatly diminished both the frequency of NK conjugates and the percentage of conjugates with detectable IgG2b FcR or asialo-GM1. These results confirm that NK cells co-express asialo-GM1 and Fc receptors, at the single-cell level, and provide a simple method for greatly enriching NK populations at least 10-fold.

Tumor progression in metastasis: an experimental approach using lectin resistant tumor variants

A novel model of tumor progression in metastatic cancer is described which grew out of attempts to derive stable non-metastatic variants from a highly metastatic mouse tumor called MDAY-D2. The variants were obtained by selection of so-called lectin-resistant (LecR) membrane mutants using toxic concentrations of wheat germ agglutinin (WGA) as the selective agent, after mutagenesis. Cloned WGAR variants almost all appeared to be highly tumorigenic and metastatic, but displayed altered growth properties which were highly suggestive of major cellular phenotypic alterations occurring prior to metastasis. This were confirmed with the discovery that spontaneous visceral metastases always consisted of WGA-sensitive (WGAS) 'revertant' tumor cells. Such revertants also arose at the site of the subcutaneous inoculation and, with time, comprised an increasing proportion of the tumor cells at that location. The WGAS/high metastatic phenotype was stable in vitro or in vivo, implying the WGAR leads to WGAS shift had an underlying genetic basis. Thus, it appeared that the WGAR tumor cells could not metastasize, because of either an intrinsic cellular defect or a host imposed barrier, but that this block could be circumvented through a genetic change in the WGAR tumor cells which was accompanied by reversion of the WGAR phenotype. Non-tumorigenic (tum-) WGAR variants were also obtained, but in these cases the mutagenesis treatment itself appeared responsible for development of the tum- phenotype. The reduced tumorigenicity had an underlying immunological basis, a finding which could be exploited to immunotherapeutically treat established visceral metastases of poorly immunogenic tumors. Throughout these studies, emphasis was placed on the considerable potential of using tumor cell populations having various stable drug-resistant genetic markers to monitor aspects of tumorigenesis, tumor progression, and metastasis.

EA rosettes using IgG monoclonal antibody-coated erythrocytes: degree of rosette formation correlates with the amount of antibody on the erythrocytes

The EA (Fc receptor) rosetting assay, which utilizes sheep erythrocytes (SRBC) coated with anti-SRBC antibodies as indicator cells (EA) is a rapid and convenient method for the detection of Fc-receptor-positive cells. To prevent haemagglutination of the EA indicator cells, it has been necessary to dilute conventional SRBC antisera. Owing to this technical restriction, it has not been possible to determine accurately the contribution of antibody density on the EA indicator cells to the level of Fc-receptor-positive cells measured in the EA rosetting assay. However, the availability of high-titred non-haemagglutinating monoclonal anti-SRBC antibodies has provided a means of examining this problem. Four non-haemagglutinating monoclonal anti-SRBC IgG preparations-two of the IgG2a subclass, an IgG2b subclass-specific and an IgG1 subclass-specific antiserum-were used to coat SRBC at antisera dilutions ranging from 1/20 to 1/2000. The amount of antibody bound to the SRBC was determined by an indirect radioimmunoassay utilizing 125I-labelled protein A. The four monoclonal anti-SRBC antibodies were shown to have unique affinities for the erythrocytes, and each was specific for antigens present in differing amounts on the SRBC. The number of Fc-receptor-positive cells detected in a spleen cell suspension or in a homogeneous Fc-receptor-positive tumour cell population by the EA (Fc) rosetting assay was found to be directly proportional to the amount of monoclonal antibody (regardless of the IgG subclass) bound to the EA indicator cells.

Membrane-associated alterations detected in poorly tumorigenic lectin-resistant variant sublines of a highly malignant and metastatic murine tumor

A number of wheat germ agglutinin-resistant (WGAR) variants of a highly malignant and metastatic mouse tumor (called MDAY-D2) were selected. Two of these, MDW1 and MDW3, were poorly tumorigenic in the normal DBA/2 host but grew well in highly immunosuppressed recipients. In contrast, MDAY-D2, MDW4, and MDW5 were all highly tumorigenic in both normal and immunosuppressed hosts. Analysis of the WGAR variants by cytotoxic T-cell testing did not reveal any evidence for the acquisition of new tumor antigens by the MDW1 or MDW3 variant sublines, although they provoked a significantly stronger T killer cell response than did MDAY-D2, MDW4, or MDW5. Further studies indicated that the rate of tumor cell surface shedding in vitro correlated strongly with relative tumorigenicity and, furthermore, that changes in the cytoskeletal structure of MDW1 and MDW3 may have contributed to their reduced rate of shedding.

The relationship between peak inspiratory pressure and positive end expiratory pressure on the volume of air lost through a bronchopleural fistula

A bronchopleural fistula (BPF) may complicate the management of patients with major pulmonary disease or thoracic surgery. Neonates with idiopathic respiratory distress syndrome and requiring ventilation are especially susceptible to pulmonary barotrauma, which may result in a BPF. Morbidity and mortality are consistently high. In ventilating patients with BPF, the effects of peak inspiratory pressure (PIP) and positive and expiratory pressure (PEEP) on air leak have not been documented. These relationships were studied in rabbits prepared by thoracotomy and creation of a standardized BPF. Randomized trials of various levels of PIP and PEEP were applied, and the percent of inspired tidal volume lost through the BPF calculated. The percent of inspired volume lost does not increase significantly from 10 to 30 cm H2O PIP (p greater than 0.05). Percent leak does increase significantly when increasing PEEP frm 0 to 16 cm H2O (p less than 0.001). Any PEEP greater than 6 cm H2O results in more air loss through the BPF than any level of PIP (p less than 0.01). Linear regressions through a common origin were calculated to illustrate the relationship of PIP versus leak and PEEP versus leak. The slopes of these lines (0.572 and 3.97, respectively) are significantly different (p less than 0.001). When using equal increments of PIP and PEEP, PEEP will have over a sixfold greater effect on air leak than doses PIP. These data suggests that PIP should be increased preferentially when ventilating patients with BPF in order to minimize air leak. PEEP less than 6 cm H2O can be used without any significant increase in the volume of air lost.