[Update on collaborative autopsy-based research in German pathology, neuropathology, and forensic medicine]

BACKGROUND

Autopsies are a valuable tool for understanding disease, including COVID-19.

MATERIALS AND METHODS

The German Registry of COVID-19 Autopsies (DeRegCOVID), established in April 2020, serves as the electronic backbone of the National Autopsy Network (NATON), launched in early 2022 following DEFEAT PANDEMIcs.

RESULTS

The NATON consortium's interconnected, collaborative autopsy research is enabled by an unprecedented collaboration of 138 individuals at more than 35 German university and non-university autopsy centers through which pathology, neuropathology, and forensic medicine autopsy data including data on biomaterials are collected in DeRegCOVID and tissue-based research and methods development are conducted. More than 145 publications have now emerged from participating autopsy centers, highlighting various basic science and clinical aspects of COVID-19, such as thromboembolic events, organ tropism, SARS-CoV‑2 detection methods, and infectivity of SARS-CoV-2 at autopsy.

CONCLUSIONS

Participating centers have demonstrated the high value of autopsy and autopsy-derived data and biomaterials to modern medicine. The planned long-term continuation and further development of the registry and network, as well as the open and participatory design, will allow the involvement of all interested partners.

[Neurofibroma in Children hand - Case Report and Literature Review]

Neurofibromas rarely occur before the age of 7 in children. They are a rarity on the hand, especially if they are accompanied by sensory disturbances and impairment of the gripping function. We report on a 9-year-old girl with symptomatic neurofibroma of the third and fourth ray of the right palm.

Only strongly enhanced residual FDG uptake in early response PET (Deauville 5 or qPET ≥ 2) is prognostic in pediatric Hodgkin lymphoma: Results of the GPOH-HD2002 trial

PURPOSE

In 2014, we published the qPET method to quantify fluorodeoxyglucose positron emission tomography (FDG-PET) responses. Analysis of the distribution of the quantified signals suggested that a clearly abnormal FDG-PET response corresponds to a visual Deauville score (vDS) of 5 and high qPET values ≥ 2. Evaluation in long-term outcome data is still pending. Therefore, we analyzed progression-free survival (PFS) by early FDG-PET response in a subset of the GPOH-HD2002 trial for pediatric Hodgkin lymphoma (PHL).

PATIENTS/METHODS

Pairwise FDG-PET scans for initial staging and early response assessment after two cycles of chemotherapy were available in 93 PHL patients. vDS and qPET measurement were performed and related to PFS.

RESULTS

Patients with a qPET value ≥ 2.0 or vDS of 5 had 5-year PFS rates of 44%, respectively 50%. Those with qPET values < 2.0 or vDS 1 to 4 had 5-year PFS rates of 90%, respectively 80%. The positive predictive value of FDG-PET response assessment increased from 18% (9%; 33%) using a qPET threshold of 0.95 (vDS ≤ 3) to 30% (13%; 54%) for a qPET threshold of 1.3 (vDS ≤ 4) and to 56% (23%; 85%) when the qPET threshold was ≥ 2.0 (vDS 5). The negative predictive values remained stable at ≥92% (CI: 82%; 98%).

CONCLUSION

Only strongly enhanced residual FDG uptake in early response PET (vDS 5 or qPET ≥ 2, respectively) seems to be markedly prognostic in PHL when treatment according to the GPOH-HD-2002 protocol is given.

[The innate immune system in oropharyngeal squamous cell carcinoma : Immune modulation by HPV]

Based on clinical and experimental data, oropharyngeal squamous cell carcinomas (OPSCC) associated with human papillomavirus (HPV) have been recognized as a distinct entity of head and neck cancers. However, outside of clinical trials, HPV status currently has no impact on treatment. The natural replication cycle of HPV takes place in epithelial cells, and is thus spatially separated from cytotoxic immune cells in the epidermis. Dendritic cells (Langerhans cells, LC), however, are frequent in this upper dermal layer. The ability of LC to process antigens, migrate, and, ultimately activate T cells is inhibited by the activity of the viral oncoproteins (E5-E7). Downregulation of functional human leukocyte antigen I (HLA-I) epithelial cell surface expression contributes to LC inhibition. However, due to their absence in upper skin layers, corresponding activation of natural killer (NK) cells via missing-self recognition is not relevant. Genome-wide analyses have revealed specific expression signatures for HPV-associated OPSCC that are distinct from HPV-negative cancers. Interestingly, aberrations in HLA-I genes were common in HPV-associated OPSCC. Our own findings indicate more frequent infiltration of HPV-associated OPSCC by CD56-positive (CD56⁺) NK cells, which might be related to HLA-I downregulation during HPV-associated carcinogenesis. In patients with OPSCC, CD56 positivity correlates with improved prognosis after conventional therapy. This could be evidence for HPV-associated OPSCC being especially eligible for novel immune-based therapies and an indication that immunological data should be included in the design of clinical trials.

[Disseminated osteolytic lesions in a 28-year-old refugee]

A 28-year-old Syrian refugee presented with right-sided knee pain and progressive deterioration of the general condition over the past months. Laboratory diagnostics revealed severe hypercalcemia due to primary hyperparathyroidism, and computed tomography (CT) scanning demonstrated disseminated osteolytic lesions throughout the skeleton. Histologically, these lesions were characterized by multinuclear giant cells (defining these lesions as so-called brown tumors). Finally, surgical removal of a jugular mass allowed the histopathologic diagnosis of a sporadic parathyroid carcinoma. In the patient, this condition was associated with a mutation in the HPRT2 gene locus.

Unusual gastric mucosal infiltration by a medullary thyroid carcinoma: a case report

Background

Medullary thyroid carcinoma accounts for approximately 1 to 2 % of all thyroid carcinoma cases. The most common route of dissemination is to locoregional lymph nodes. Distant metastases commonly affect bones, lungs, and liver. We present a case of a white woman with a 25-year history of medullary thyroid carcinoma on multiple medications including tyrosine kinase inhibitor therapy for the last 11 months, who exhibited unusual diffuse infiltration of advanced stage medullary thyroid carcinoma to her gastric mucosa.

Case presentation

A 53-year-old white woman presented with increasing fatigue, loss of appetite, and severe epigastric pain radiating to her back. She had a history of medullary thyroid carcinoma (pT2pN1b), diagnosed 25 years ago and treated by complete thyroidectomy and repeated bilateral cervical lymph node dissection. Medical therapy included octreotide 20 mg every 4 weeks, which was switched to the tyrosine kinase inhibitor vandetanib 300 mg/day 11 months ago when computed tomography scanning revealed progressive mediastinal lymph node and diffuse and symptomatic pulmonary metastases. Of note, she demonstrated macroscopically stable pulmonary and mediastinal lymph node metastases; however, her calcitonin serum levels dramatically increased. Computed tomography scanning revealed a single new intrahepatic lesion (4 mm) as well as multiple (>10) new supraclavicular lesions suggestive of medullary thyroid carcinoma progress. As proven by gastric biopsy and immunohistochemical evaluation, her epigastric pain was explained by a diffuse infiltration of her gastric mucosa by metastatic medullary thyroid carcinoma. Subsequently, she rapidly deteriorated and died.

Conclusions

The current case report shows for the first time an unusual metastatic infiltration of the gastric mucosa by medullary thyroid carcinoma. When treating these patients, it is important to include this differential diagnosis during follow-up.

Electronic supplementary material

The online version of this article (doi:10.1186/s13256-016-0981-9) contains supplementary material, which is available to authorized users.

Lévy Flights due to Anisotropic Disorder in Graphene

We study transport properties of graphene with anisotropically distributed on-site impurities (adatoms) that are randomly placed on every third line drawn along carbon bonds. We show that stripe states characterized by strongly suppressed backscattering are formed in this model in the direction of the lines. The system reveals Lévy-flight transport in the stripe direction such that the corresponding conductivity increases as the square root of the system length. Thus, adding this type of disorder to clean graphene near the Dirac point strongly enhances the conductivity, which is in stark contrast with a fully random distribution of on-site impurities, which leads to Anderson localization. The effect is demonstrated both by numerical simulations using the Kwant code and by an analytical theory based on the self-consistent T-matrix approximation.

[Fractal geometry in the objective grading of prostate carcinoma]

BACKGROUND

A possible approach to objectively classify complex patterns in tumor tissue is a mathematical and statistical investigation of the distribution of cell nuclei as a geometric representation of cancer cells by fractal dimensions. Both the existence and changes in the fractal structure of tumor tissue have important consequences for the objective system of tumor grading. In addition, the complexity of growth in different carcinomas or their intercellular interactions can be compared to each other.

RESULTS

We present a theoretical introduction into fractal geometry as well as in the computer algorithms based upon the Rényi family of fractal dimensions. Finally, a geometric model of prostate cancer is introduced and the relationship between geometric patterns of prostate tumor and the fractal dimensions of the Rényi family are explained.

[Objective grading of prostate carcinoma based on fractal dimensions: Gleason 3 + 4= 7a ≠ Gleason 4 + 3 =7b]

BACKGROUND

Significant intra- and interobserver variability ranging between 40 and 80% is observed in tumor grading of prostate carcinoma. By combining geometric and statistical methods, an objective system of grading can be designed.

MATERIAL AND METHODS

The distributions of cell nuclei in two-dimensional patterns of prostate cancer classified subjectively as Gleason score 3+3, 3+4, 4+3, 4+4, 4+5, 5+4, and 5+5 were analyzed with algorithms measuring the global fractal dimensions of the Rényi family and with the algorithm for the local connected fractal dimension (LCFD).

RESULTS

The dimensions for global fractal capacity, information, and correlation (standard deviation) were 1.470 (045), 1.528 (046), and 1.582 (099) for homogenous Gleason grade 3 (n = 16), 1.642 (034), 1.678 (041), and 1.673 (084) for homogenous Gleason grade 4 (n=18), and 1.797 (042), 1.791 (026), and 1.854 (031) for homogenous Gleason grade 5 (n=12), respectively. The LCFD algorithm can be used to distinguish both qualitatively and quantitatively between mixed and heterogeneous patterns, such as Gleason score 3+4=7a (intermediate risk cancer) and Gleason score 4+3=7b (high-risk cancer). Sensitivity of the method is 89.3%, and specificity 84.3%.

CONCLUSION

The method of fractal geometry enables both an objective and quantitative grading of prostate cancer.

Quantum Hall criticality and localization in graphene with short-range impurities at the Dirac point

We explore the longitudinal conductivity of graphene at the Dirac point in a strong magnetic field with two types of short-range scatterers: adatoms that mix the valleys and "scalar" impurities that do not mix them. A scattering theory for the Dirac equation is employed to express the conductance of a graphene sample as a function of impurity coordinates; an averaging over impurity positions is then performed numerically. The conductivity σ is equal to the ballistic value 4e2/πh for each disorder realization, provided the number of flux quanta considerably exceeds the number of impurities. For weaker fields, the conductivity in the presence of scalar impurities scales to the quantum-Hall critical point with σ≃4×0.4e2/h at half filling or to zero away from half filling due to the onset of Anderson localization. For adatoms, the localization behavior is also obtained at half filling due to splitting of the critical energy by intervalley scattering. Our results reveal a complex scaling flow governed by fixed points of different symmetry classes: remarkably, all key manifestations of Anderson localization and criticality in two dimensions are observed numerically in a single setup.

[A 75-year-old female patient with pleural effusion and gastric metastases of a poorly differentiated carcinoma]

A 75-year-old woman was found to have left-sided pleural effusion and endoscopy revealed the rare entity of adenoid cystic carcinoma metastases in the gastric mucosa. Approximately 20% of patients with this carcinoma suffer from distant metastases. For the initial staging detection of adenoid cystic carcinoma metastasis with positron emission tomography (PET) or PET computed tomography (CT) is recommended. The recurrent t(6;9)(q22-23;p23-24) translocation that results in a fusion of the two transcription factor genes MYB and NFIB is detectable in half of the cases. As in our case molecular pathology can confirm the correct diagnosis and identification of the localization of the primary tumor.

[Splenomegaly with multiple unclear parenchymal lesions. Splenomegaly]

A 53-year-old female patient presented with splenomegaly, uncertain lesions of the spleen, pancytopenia and suspected aortitis. Reduced strength and muscular pain but no B symptoms were also present. Alterations of the spleen had been known for a long time. Blood examination, laboratory tests and magnetic resonance imaging (MRI) confirmed an aortitis. Concerning the splenic changes neither ultrasound nor MRI could provide conclusive or even pathognomonic findings. Because of an existing pancytopenia and diagnostic obscurity, the patient underwent splenectomy. The histological diagnosis was finally concluded as multifocal littoral cell angioma.

[Tumor microenvironment in gastrointestinal tumors]

The growing potential of modern molecular analysis tools has led to a sharp increase in the understanding of the molecular dimension of pathological processes and, consequently, to a growing influence of pathological diagnoses on the selection of therapeutic approaches. Molecular analysis tools have also led to the understanding that groups of tumors hitherto considered to belong to a single, homogeneous disease entity should rather be divided into subgroups with specific molecular attributes, growth behavior patterns and, consequently, different prognostic characteristics and therapeutic needs. A major factor contributing to the differentiation of these subgroups is the composition of the tumor microenvironment (ME), a compartment that is involved in the control of critical carcinogenetic processes such as angiogenesis and invasive growth. Consequently, the investigation of the ME promises to be a most auspicious field of research for pathologists and there is hope that the increased understanding of the interaction between neoplastic cells and the ME will lead to improved diagnostic tools and novel therapeutic approaches for the treatment of cancer patients.

Absence of Epstein-Barr virus in the brain and CSF of patients with multiple sclerosis

OBJECTIVE

Epstein-Barr virus (EBV) is a ubiquitous human herpesvirus that becomes latent in B-lymphocytes and has been implicated in the pathogenesis of multiple sclerosis (MS). We searched for latent and active EBV infection in MS brain and CSF.

METHODS

Nested and non-nested real-time PCR were used to detect cell-specific and EBV-specific transcripts in 15 fresh-frozen and 5 formalin-fixed paraffin-embedded MS plaques and in single MS CSF B-lymphocytes and plasma cells. Intrathecal anti-EBV antibody synthesis was measured by ELISA. Immunocytochemistry was used to detect binding of MS CSF and recombinant antibodies (rAbs) generated from clonally expanded plasma cells in MS CSF to EBV-infected cells.

RESULTS

No EBV RNA was found in MS CSF B-lymphocytes or plasma cells. In active MS plaques, EBV-encoded RNA (EBER)-1 was the only and rarely detected transcript. The frequency of detected intrathecal anti-EBV antibody synthesis in patients with MS did not differ from that in non-MS inflammatory CNS disease control patients. Anti-EBV antibodies were detected in the CSF of patients with MS, but MS rAbs did not react with EBV.

CONCLUSIONS

Application of real-time PCR to multiple sclerosis brain and single B-lymphocytes in CSF did not reveal any evidence of active Epstein-Barr virus infection.

A human recombinant autoantibody-based immunotoxin specific for the fetal acetylcholine receptor inhibits rhabdomyosarcoma growth in vitro and in a murine transplantation model

Rhabdomyosarcoma (RMS) is the most common malignant soft tissue tumor in children and is highly resistant to all forms of treatment currently available once metastasis or relapse has commenced. As it has recently been determined that the acetylcholine receptor (AChR) gamma-subunit, which defines the fetal AChR (fAChR) isoform, is almost exclusively expressed in RMS post partum, we recombinantly fused a single chain variable fragment (scFv) derived from a fully human anti-fAChR Fab-fragment to Pseudomonas exotoxin A to generate an anti-fAChR immunotoxin (scFv35-ETA). While scFv35-ETA had no damaging effect on fAChR-negative control cell lines, it killed human embryonic and alveolar RMS cell lines in vitro and delayed RMS development in a murine transplantation model. These results indicate that scFv35-ETA may be a valuable new therapeutic tool as well as a relevant step towards the development of a fully human immunotoxin directed against RMS. Moreover, as approximately 20% of metastatic malignant melanomas (MMs) display rhabdoid features including the expression of fAChR, the immunotoxin we developed may also prove to be of significant use in the treatment of these more common and most often fatal neoplasms.

Neurosurgical aspects of childhood hypophosphatasia

OBJECTIVE

Hypophosphatasia (HPP; MIM241510) is a rare inborn error of bone metabolism of recessive inheritance. It is caused by mutations in the gene encoding the tissue-nonspecific alkaline phosphatase. Apart from problems in bone mineralization, growth failure, and premature loss of decidual teeth, the infantile and the childhood types of HPP are associated with premature fusion of cranial sutures.

PATIENTS

We report on seven children affected with infantile and childhood HPP who presented with craniosynostosis.

RESULTS

Neurosurgical intervention was necessary in four of them because of intracranial hypertension. In one of these, severe dural calcification posed an unexpected problem during surgery. Secondary ectopia of the cerebellar tonsils were detected in five of the seven patients and caused hydrosyringomyelia in one of them.

CONCLUSIONS

Since cranial sutures are frequently involved in infantile and childhood HPP, a multidisciplinary approach for the clinical care is necessary, including long-term neurosurgical surveillance.

Cutaneous dissemination of nasal NK/T-cell lymphoma in a young girl

In Europe and the USA, the incidence of primary nasal natural killer (NK)/T-cell lymphoma is rare. The skin is one of the predilection sites for dissemination. Cutaneous dissemination is a poor prognostic sign and is consistently fatal. We describe the case of a 17-year-old white German girl with a primary nasal NK/T-cell lymphoma and cutaneous dissemination. She presented with multiple maculopapular patches involving the trunk and thighs, and a 4-week history of headache, fever and fatigue. Biopsies of the skin and the nasal mucosa were taken. Pathological examination of both specimens revealed a NK/T-cell lymphoma. Epstein-Barr virus RNA was detected in the lymphoma cells by in situ hybridization. Unfortunately, the patient died of disease within 1 week.

[Tumor-type specific translocations methods and indications for routine molecular pathology]

Chromosomal abnormalities like translocations and their corresponding gene fusions were first suggested to be causal factors in the development of cancer by Boveri in 1914. At present more than 350 gene fusions involving 337 different genes have been identified and in particular in malignant hematological diseases and sarcomas an increasing number of chromosomal aberrations are being recognized as important diagnostic and prognostic parameters. By contrast this type of gene rearrangement has been until recently only rarely described in the common carcinomas. However, with new powerful techniques, that enable the detection of cytogenetically cryptic rearrangement, this number is likely to increase substantially and carcinomas characterized by fusions oncogenes indicate that the pathogenetic mechaisms involved in epithelial carcinogenesis may be similar to those known to operate in hematological and soft-tissue malignancies.

Maligne hämatopoetische Systemerkrankungen

The moleculargenetic detection of specific genetic abnormalities within malignant hematopoietic disorders is an important diagnostic tool with relevance for the differential diagnosis, therapy and prognosis.According to a modified and optimized RT-PCR based technique native bone marrow aspirates and peripheral blood samples of 183 patients were investigated for the presence of specific genetic abnormalities. The histological diagnosis of all CMLs t(9;22) and variants of AMLs M3 t(15;17) and t(11;17) were moleculargenetically confirmed. Additionally one t(5;12) positive chronic myelomonozytic leukemia, one t(8;21) positive AML M1, one t(9;22) positive B-ALL and in each case one t(6;9) and one t(3;21) positive myelodysplastic syndrome were detected. The hereby described method is a simple, specific and reliable technique for the rapid moleculargenetic detection of specific genetic abnormalities within malignant hematopoietic disorders with implication for the diagnosis/differential diagnosis, prognosis and therapy.

[Rhabdomyosarcoma lysis by T cells expressing a human autoantibody based chimeric receptor targeting the fetal acetylcholine receptors]

Rhabdomyosarcomas (RMSs) are the most frequent malignant soft tissue tumors of childhood. Since even aggressive multimodality treatments including autologous stem cell rescue have failed to improve the < 20 % overall survival rate of children with metastatic RMS, novel treatment approaches are urgently needed. Looking for potential targets for immunotherapies, we identified the gamma subunit of the fetal acetylcholine receptor (fAChR) as a specific and overexpressed membrane antigen in RMS. Additionally we established a duplex RT-PCR with simultaneous amplification of alpha and gamma subunit message of the fAChR and the quantification of both transcripts resulting in alpha/gammaAChR ratio > 1 was 100% sensitive in alveolar and embryonal rhabdomyosarcoma. Since the fAChR was the first extracellular tumor marker that can distinguish rhabdomyosarcomas from nonrhabdomyomatous tumors and from normal muscle and therefore implies, that the fAChR may be a target for immunotherapeutic strategies, we synthesized a scFv antibody fragment directed against the fAChR and enigineered both a Pseudomonas exotoxin A based immunotoxin as well as a chimeric T cell receptor composed of the antigen-binding domain of the scFv fragment joined to the signaling domain of the T cell receptor zeta chain. The interaction of fAChzeta-transduced T cells with several RMS cell lines but not with fAChR-negative controls induced strong T cell activation, characterized by secretion of high amounts of interferon-gamma. Moreover after co-incubations with RMS cell lines fAChRzeta-transduced T cells as well fAChR specific immunotoxin induced specific receptor-concentration dependent tumor cell lysis. Therefore, fAChRzeta-transduced T cells and the fAChR specific immunotoxin respectively are promising new tools for the immunotherapy of rhabdomyosarcomas and may provide an effective complementary approach to eradicate residual or metastatic RMS cells in patients, since 1. RMS-direceted chemotherapies increase the expression of fAChR on residual RMS cells in vivo and 2. the fully human fAChR autoantibody fragment with low immunizing potential allows prolonged/permanent application of fAChRzeta-transduced T cells/immunotoxin.

[Gastrointestinal stromal tumor of the abdominal wall. An unusual localization of a rare tumor]

Gastrointestinal stromal tumors (GIST) are the most common mesenchymal tumors of the gastrointestinal tract. We describe here for the first time a patient with a huge GIST of the abdominal wall without any relation to the gastrointestinal tract, omentum, or mesentery. With regard to the size of 24 cm and a low mitotic index, this GIST is considered an intermediate risk for metastasis. Radical surgical resection was performed with negative pathologic resection margins. The classic immunohistochemical phenotype of the tumor described facilitates the differential diagnosis to exclude abdominal desmoid tumor and solitary fibrous tumor (SFT). In the case of metastasis, therapeutic nihilism no longer seems justified with the availability of imatinib, a tyrosine kinase inhibitor, which shows encouraging results in the therapy of metastatic GIST.

Transcription of the nude gene (WHN) in human normal organs and mediastinal and pulmonary tumors

Mutations in the winged-helix-nude (WHN) gene in the nude mouse and rat phenotypes lead to loss of hair and athymia. The human nude gene has recently been identified, but to date, its distribution in normal human tissues and thymus tumors has not yet been investigated. We used the RT-PCR technique for the detection of WHN transcripts in normal human organs and various mediastinal tumors, including various subtypes of thymic epithelial tumors. We could show that WHN is highly transcribed in the normal thymus and skin. Unexpectedly, few transcripts were also found in the normal kidney and thyroid gland. WHN mRNA could be detected in all thymoma subtypes (n = 14) and epidermoid thymic carcinomas as well as in all squamous cell carcinomas of the lung (n = 5) investigated, but was totally absent in all other mediastinal tumors (n = 11) lacking an epidermoid differentiation. We conclude that transcription of the human WHN is not strictly specific for human thymus and skin, but is also expressed, though at very low levels, in the normal human kidney and thyroid gland. In addition, WHN gene expression may identify not only thymomas but also epidermoid differentiation in mediastinal and pulmonary tumors.

Reversible monoclonal lymphadenopathy in autoimmune lymphoproliferative syndrome with functional FAS (CD95/APO-1) deficiency

The FAS (CD95/APO-1) receptor and its ligand play an important role in the initiation of apoptosis under many physiologic conditions. Loss of function mutations of the FAS gene have been described in lpr mice and in humans with autoimmune phenomena, recurrent lymphadenopathies, and hepatosplenomegaly. This syndrome is now called autoimmune lymphoproliferative syndrome type I (ALPS I). Recently, patients with similar clinical symptoms due to a functional FAS deficiency without FAS gene mutations have been distinguished. This disease has been termed autoimmune lymphoproliferative syndrome type II (ALPS II) or autoimmune lymphoproliferative disease (ALD). This report is the first description of the lymph node pathology and immunohistochemistry in a patient with ALPS II. After recurrent bacterial infections, a 4-year-old child developed cervical giant lymphadenopathy suggesting lymphoma. Lymph node histology resembled the findings in Epstein Barr virus-associated posttransplant atypical lymphoproliferations. Confluent sheets of immunoblasts, however, showed a monoclonal expression of IgG/lambda and a monoclonal rearrangement of the JH chain. The same clone was also present in the peripheral blood. Although high-grade lymphoma could not be excluded, the patient's parents insisted on the patient's leaving the hospital with only antibiotic treatment. Surprisingly, the giant lymphadenopathy completely resolved within 7 weeks, and the clone was no longer detectable in the peripheral blood. Twelve months later the patient was still free from lymphoma and was doing well. Retrospectively, transient monoclonal B-cell populations could be identified in an archival frozen blood sample taken when the patient was 3 years old. Increased FAS-independent spontaneous apoptosis was a feature of the patient's lymphocytes and could be the molecular basis for self-elimination of B-cell clones. We conclude that the diagnosis of a FAS-FAS-L deficiency should be considered in children with an otherwise unexplained atypical lymphoproliferation and that a diagnosis of lymphoma in patients with functional FAS deficiency should be made with considerable reservation.

[Comparison of the transcription of the fetal type acetylcholine receptor and myogenin in rhabdomyosarcoma]

Myogenin and the fetal type acetylcholine receptor (AChR) subunits are specific immunohistochemical markers for the diagnosis of rhabdomyosarcomas. In spite of light microscopy and immunohistochemistry, the diagnosis of doubtful cases and small biopsies of rhabdomyosarcomas remains a challenge. Therefore, a PCR-based highly sensitive approach, would be a valuable diagnostic adjunct and should be free from the risk of contamination of the tumor sample with normal tissue. We studied the transcription of myogenin and fetal type AChR in rhabdomyosarcomas, other childhood and adult tumors and normal tissues. In all embryonal and alveolar rahbdomyosarcomas transcripts of both myogenin and fetal type AChR could be detected. The detection of myogenin mRNA however was not specific for rhabdomyosarcomas but occurred in normal muscle and the majority of other normal tissues and childhood tumors. In contrast the transcription of fetal type AChR, which is defined by an alpha subunit AChR/gamma subunit AChR ratio < 1 was encountered only in rhabdomyosarcomas and denervated muscle. Therefore we suggest, that mRNA of the fetal type AChR but not myogenin is a highly specific and sensitive target for the PCR-based diagnosis of rhabdomyosarcomas.

Polymerase chain reaction-based diagnosis of rhabdomyosarcomas: comparison of fetal type acetylcholine receptor subunits and myogenin

The diagnosis of rhabdomyosarcoma (RMS) is usually straight-forward when light microscopy and immunohistochemistry are used. However, tumors that exhibit a low degree of differentiation and small biopsies can lead to confusion. In such patients and for the detection of minimal (residual) disease, a polymerase chain reaction (PCR)-based approach would be a valuable diagnostic adjunct. This type of approach would be highly sensitive and should be free from the risk for contamination of the tumor sample with normal tissue. Because myogenin and the alpha and gamma subunit of the fetal type acetylcholine receptor (AChR) are specific immunohistochemical markers for RMS, their expression on the mRNA level in RMS, other childhood and adult tumors, and normal tissues was studied. Although the sensitivity of both approaches was 100% in embryonal and alveolar RMS, detection of myogenin mRNA was not specific for RMS but occurred in normal muscle and the majority of the other normal tissues and childhood tumors. Conversely, detection of fetal AChR mRNA as defined by an alpha/tau ratio of < 1 was encountered only in RMS and denervated muscle. The authors conclude that mRNA of the fetal type AChR but not myogenin is a highly specific and sensitive target for the PCR-based diagnosis of RMS.

Pathogenesis of myasthenia gravis

Various studies over the last 25 years in Man and animal models have revealed many steps in the pathogenesis of myasthenia gravis (MG) which is now considered the classical organ specific, autoantibody mediated and T cell dependent human autoimmune disease. Though not a disease entity, MG is associated with pathological alterations of the thymus in about 80% of cases. These are described here with reference to distinct models of autoimmunization against the acetylcholine receptor (AChR). In MG with thymitis, intrathymic production of AChR-specific autoantibodies is the result of a classical antigen-driven immune reaction that occurs completely inside the thymus and probably involves AChR on myoid cells as the triggering (myasthenogenic) antigen. Genetic factors contribute essentially to the pathogenesis of this form of MG. In thymoma-associated MG genetic factors are probably of marginal significance. Neither intratumour autoantibody production nor T cell activation seem to occur and the AChR is not the myasthenogenic antigen. Instead, abnormal neurofilaments that share epitopes with the AChR and other auto-antigen targets in paraneoplastic MG are expressed in thymomas and may trigger autoantigen-specific, non-tolerogenic T cell selection by molecular mimicry. These data support the hypothesis that initial steps in the pathogenesis of most MG cases take place within abnormal thymic microenvironments, be they inflammatory or neoplastic. Where these initial steps occur in MG cases without thymic pathology is not known. Likewise, the factors involved in the initial triggering of MG remain enigmatic in all MG subtypes.

[Absence of herpesvirus saimiri STPC oncogene in salivary gland tumors and epithelial thymus tumors]

AIM AND METHODS

The oncoprotein STP-C-488 induces salivary gland and thymic epithelial tumours when expressed as a transgene in mice (MURPHY et al. 1994). Given the enigmatic tumorigenesis of corresponding tumours in humans, we now investigated genomic DNA and RNA from 11 thymomas, 5 pleomorphic adenomas and control autopsy material (n = 8) for the occurrence of the STP-C-488 sequences by Southern-blotting, Northern-blotting and PCR.

RESULTS

All tumor samples and control tissues were negative for the STP-C-488 in Southern-blot and Northern-blot-hybridization. PCR analyses did not reveal amplification products of the length expected for STP-C-488. However, a PCR fragment of a different size was found in 50% of the thymomas and pleomorphic adenomas, but in only one of 8 controls. The sequence of this PCR product revealed local homologies with various herpesviruses.

CONCLUSION

The oncoprotein STP-C-488 is not involved in the tumorigenesis of human thymomas and salivary gland tumours. Whether the novel sequences amplified preferentially from these tumours play a role in pathogenesis needs further investigation.