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To classify as breast cancer with neuroendocrine differentiation a growth pattern as encountered in well differentiated (G1, G2) neuroendocrine tumors (NET) of the gastrointestinal tract and the lung must be present in addition to the immunohistochemical expression of neuroendocrine markers (chromogranin, synaptophysin). The majority of breast cancers fulfilling these criteria show hormone receptor positivity and with regard to prognosis resemble luminal type of breast cancer from which they are not fundamentally different. Despite lacking clinical relevance the up-coming WHO classification of breast cancer will nevertheless introduce the new category of NET luminal type. Immunohistochemical detection of neuroendocrine marker alone cannot be considered as sufficient for classification because it can frequently be encountered in other types of breast cancer (e.g. mucinous, solid papillary). From low grade NET with good differentiation those with poor differentiation and most frequently small cell appearance have to be differentiated. Poorly differentiated NET can primarily originate in the breast, which may be indicated by intraductal growth and co-expression of GATA3 but in these cases metastasis of extra mammary cancers has to be considered and correlation with the clinical findings is required for correct classification.

Ectopic breast tissue may represent the complete breast (accessory breast), glandular tissue without areola or nipple (aberrant breast tissue), or exclusively the nipple (polythelia). Localization is along the embryonic milk ridge extending from the axilla to the vulva. Only rarely, is ectopic tissue found outside of the milk ridge. Most frequently affected are the axilla, the breast itself, and its close neighbourhood. Ectopic breast tissue may rarely give rise to tumours such as fibroadenoma or carcinoma.

Congenital syphilis is a rare disease in central Europe. Placental changes may be non-specific but a typical finding is necrotizing funisitis of the umbilical cord. In a case report we describe how the histopathological incidental finding of B lymphocyte-rich, necrotizing funisitis led to the diagnosis of a previously unknown Treponema pallidum infection in parents and their newborn child. The pathological suspicion of congenital syphilis, although rare, has implications for the clinical management (serological evaluation of parents and child as well as the social environment, evaluation of viral coinfection and treatment decision) and is a notifiable disease.

Valid HER2 testing is essential for the optimal care of patients with HER2-positive gastric cancer and the correct use of first-line treatment. Although all cases of breast cancer are routinely tested for the HER2 status, HER2 testing in gastric cancer has still not become part of the routine and is usually only done upon request by the therapist. An interdisciplinary group of German experts has taken on the challenges of HER2 testing in gastric cancer as an opportunity to address essential aspects and questions on the practical use of HER2 testing in this indication from the perspective of pathologists and therapists. The recommendations made in this article reflect the consensus of all participants and correspond to their opinions and long-term experience.

Whereas in many fields of surgical pathology examination of cytological smears and analysis of histological tissue sections provide alternative methods which are chosen according to the clinical requirements, in hematopathology both types of morphological investigation are routinely applied in parallel and simultaneously. This procedure improves the diagnostic precision and safety. Unlike other European countries in Germany both procedures are performed by different specialties. Cytology is the responsibility of hematologists whereas histology is carried out by pathologists, which interferes with an integrative diagnostic approach unless intense communication takes place. Ideally, in the diagnosis of hematological disorders histology of bone marrow trephines should be studied in conjunction with smears of peripheral blood and bone marrow. In many instances, further complementary investigations, such as flow cytometry, cytogenetics and increasingly molecular pathological studies are necessary to guarantee an adequate modern state of diagnostics in hematopathology.

Gene expression profiling has demonstrated the prognostic relevance of genes associated with proliferation in breast cancer. The immunohistochemical marker Ki-67 enables routine assessment of proliferation activity in pathology. In a number of retrospective but only few prospective studies the prognostic relevance of Ki-67 in breast cancer could be shown. Although there is no standardized approach with regard to which area of a histological section and how many cells should be counted in a quantitative or semiquantitative fashion as well as to the threshold, Ki-67 is broadly applied in breast pathology. This can be explained by the good reproducibility of the degree of proliferation assessed by Ki-67, at least in the low and high ranges, the possibility to substantiate grading and better practicability in core biopsies in comparison to mitotic counting. In neoadjuvant therapy of hormone receptor positive breast cancer, Ki-67 can probably predict the efficacy of pure hormone receptor blockade without chemotherapy.

Intrauterine death is a multifactorial major complication during pregnancy. In this retrospective analysis the pathological anatomical findings of fetuses and placentas as well as maternal factors were evaluated.A retrospective screening of post-mortem examinations, corresponding placental examinations and clinical data on maternal status (1998-2008) was carried out. A classification of all findings was made with the ReCoDe system and induced abortions and cases with incomplete data were excluded from the study.A total of 84 pregnancies involving 87 fetuses (9 siblings) were evaluated. The median gestation age was 20 weeks (range 12-41). The evaluation based on the ReCoDe system revealed that intrauterine death was mainly associated with placental diseases (n = 63) and to a lesser extent with fetal malformations (n = 15) or maternal diseases (n = 4). Idiopathic cases were rare (n = 2).Placental examination is important for explaining intrauterine death because in most cases an association with placental diseases can be found but fetal malformation and maternal diseases must be taken into account.

In breast cancer, tumor biological markers are gaining impact and have become equal to traditional markers of pathology. Molecular expression profiling has led to new categories, which by receiving translation into immunohistochemical terms have entered routine pathology use. Besides the triple negative (basal) type, there are hormone receptor positive luminal A and B types and the HER2 type. The distinction between luminal A and B type is not yet clear cut and the proliferation marker Ki-67 as well as diverse RNA expression profiles are used for distinction in order to decide which patients might benefit from pure endocrine and which from combined chemo-endocrine therapy. Prospective studies are necessary to answer these questions. Study data are further awaited to clarify the heterogeneity of triple negative cases which include most of the BRCA1 associated cancers and to elucidate whether within the HER2 category, polysome or pseudopolysome cancer will respond to therapy.

Myelodysplastic syndromes (MDS) and myeloproliferative neoplasms (MPN) represent neoplastic proliferations of hematopoietic stem cells, which may progress to loss of differentiation and acute myeloid leukemia (AML). Transitions between MDSs and MPNs as well as combinations between both disorders occur and MPNs may acquire dysplastic features combined with cytopenia. Myelodysplastic/myeloproliferative neoplasms show dysplastic and myeloproliferative properties and have in common genetic aberrations at the stem cell level (TET2, ASXL 1, CBL, IDH 1, IDH 2, EZH2, p53, Runx1), which may be found in one cell or may affect different hematopoietic stem cells, expanding in parallel. Progress to AML follows a linear clonal evolution only in a subset of cases. Alternatively AML derives from secondary clones, devoid of any marker mutation or originates from a common aberrant progenitor cell which shares other but not the JAK2 ( V617F ) mutation.

The number of patients suffering from innate, acquired or iatrogenic immunodeficiency is constantly rising. Thus the number of clinically relevant infections caused by rare or unusual pathogens is also increasing. Histopathological investigations allow the identification of difficult to culture infectious agents as well as the differentiation of tissue invasive infections from superficial colonization. In this review morphological reaction patterns and their differential diagnoses of the most common bacterial, viral and mycotic infections in the lungs of immunocompromised patients are discussed.

Classic rabies is a progressive and lethal infectious disease of animals, which may be transmitted to humans. Inter-human infections are extremely rare. The present case describes transmittal of rabies virus by lung transplantation from an infected donor. Histologically, a lymphocytic encephalomyelitis with neuronal cytoplasmic inclusion bodies was found. Immunohistochemically, rabies virus antigen was detected in the central, autonomous and peripheral nervous system. By means of electron microscopy, virions were demonstrated in the brain. A central task of health care in transplantations is the detection of uncommon infectious agents and the prevention of their transmittal.

Based on data from a large multicenter phase III trial (ToGA study) trastuzumab has very recently been approved by the EMEA for metastatic gastric cancer and adenocarcinoma of the gastro-esophageal junction. Only patients with tumors which over express Her2 as defined by IHC2+ and a confirmatory FISH+ result, or IHC 3+, determined by an accurate and validated assay are eligible for trastuzumab therapy. However, testing of Her2 status by immunohistochemistry (IHC) differs from breast cancer in core aspects: 1. IHC2+/3+ is scored even though membranous staining is incomplete if membrane staining is clearly detectable even at low magnification (2.5x/5x, 3+) or medium magnification (10x/20x, 2+). 2. Additionally, membrane staining at the appropriate intensity found in at least 10% of tumor cells is restricted to resection specimens. Evaluation of Her2 in situ hybridization (ISH) is similar to breast cancer with ratio values ofor =2.0 indicating Her2 gene amplification. Taking these modifications into account and defining the HER2 positive subgroup as IHC 3+ and IHC2+/FISH+, approximately 16% of gastric cancers are considered Her2 positive, affecting mainly tumor regions with intestinal (gland forming) type carcinoma. In contrast to breast cancer, up to one-third of gastric cancers show a heterogeneous Her2 status both at IHC and ISH levels which favors bright field ISH over FISH.

Tumor biological parameters for the prediction and prognosis of invasive breast cancer are gaining in importance compared to traditional pathological categories. The immunohistochemically determined steroid hormone receptor status is not only the decisive factor influencing whether endocrine therapy (which is indicated in cases of even slight expression) is given or not, but also whether chemotherapy is considered. The Her2 status is of similar importance and needs to be analysed in every case of invasive carcinoma, whereby reproducibility, which requires greater efforts than with steroid hormone receptors, has to be assured. Probably only a small portion of breast cancers will benefit from chemotherapy. Since traditional pathological categories are not sufficient for the identification of this subgroup, there has been an intense search for alternative prognostic parameters, whereby gene expression profiling has emerged as the most promising tool. Despite minimal concordance with regard to single genes, the various profiles available converge in the identification of the proliferative signature as the prognostically most relevant. Whether histopathological grading and immunohistochemical determination of the growth fraction with Ki-67 or genetic profiling will be more reliable in the identification of the aggressive subtype has yet to be clarified in clinical studies which encompass central pathological review.

Breast cancers with a genetic BRCA1-/BRCA2 background differ from each other and sporadic cases. A specific pathological surrogate marker, however, does not exist. In this study the results of a German reference centre are reported. BRCA1 associated cancers are predominantly high grade (G3), triple negative, highly proliferative (median Ki-67 55%) and only exceptionally accompanied by lobular intraepithelial neoplasia. Cancers with a BRCA2 germ line mutation are less frequent and resemble sporadic cases with a comparably higher proliferative activity and a lack of Her2 overexpression.

As a measure of quality assurance in mammography screening in Germany, obligatory double reading of histopathological specimens is currently a subject of debate. Concordance rates of more than 6000 cases gathered from several reference centres were evaluated. In accordance with several international studies, overall agreement in single and double readings in German mammography screening was approximately 95%. Concordance rates were even higher for malignancies (99%). Variations are more common in the case of lesions, the biological significance of which remains unclear (flat atypia, lobular neoplasm, papilloma). This is the result of a currently unresolvable methodological rather classification problem, as seen from studies from countries with many years of experience in training and diagnostic test series. Thus, the evidence base is currently insufficient to mandate double reading of slides.

In the age of personalized medicine, and in addition to typing and grading, breast cancer pathologists are now also involved in determining biomarkers such as steroid hormone receptors and Her-2, which are of the utmost importance in adjuvant therapy. In order to assure quality of these biomarker assays, external proficiency testing has been implemented in Germany. Since 2002 trials have been conducted annually, with up to 180 participating laboratories. More than 85% of all participants achieved good results in clearly negative and positive cases seen in daily practice. If at all, discordant results were observed in the rarer low steroid-hormone receptor expressing tumors and Her-2 borderline cases (2+). Regular participation in interlaboratory testing leads to significantly improved immunohistochemical results, particularly in these problematic cases. Tissue microarrays (TMA) with 20-24 different breast cancer samples including cell lines meant that a huge number of pathologists were challenged with identical samples, providing the prerequisite for comparability. Participation is recommended for pathology departments involved in the service for breast units. The organizational frame work of the trials is described here. The confidence of cooperating disciplines in breast cancer biomarkers assessed by pathologists will be fostered by external proficiency testing as presented here.

Medullary carcinoma of the breast has a relatively favorable prognosis despite its malignant histopathological appearance, providing a challenge for the pathologically based diagnosis of breast cancer. Macroscopic and microscopic findings combined provide diagnostic criteria. The importance of the immunophenotype of medullary carcinoma is not well defined. Because the reproducibility of morphological criteria is limited, we conducted an immunohistochemical study in search of markers that could facilitate histopathological classification. We examined 32 medullary carcinomas in comparison with 30 high grade ductal invasive carcinomas with similar morphology using 23 different immunohistochemical markers. The results showed an overlap with the so called basal like subtype of invasive breast cancer (negativity for steroid hormone receptor, positivity for basal cytokeratins). None of the immunohistochemical markers enabled a specific discrimination between the two groups. Medullary carcinomas overexpress EGF-R more frequently (P0.004). In combining the characteristic morphological criteria and the immunohistochemical detection of the basal like phenotype and EGFR, a higher diagnostic accuracy can be achieved. The immunophenotype alone does not allow a definite classification of medullary carcinoma.

Neoadjuvant chemotherapy has been extended to earlier stages of breast carcinoma in order to increase the rate of breast conservation by downstaging. Tumour regression can be observed in up to 80% of the cases and the chemosensitivity of the individual tumour can be studied in vivo. Moreover therapy induced regression has been established as an independent prognostic parameter. Characteristic effects of chemotherapy include reduction in cell number, fibrosis, vacuolization of cytoplasm and increased nuclear pleomorphism. Grading, typing and immunohistochemical properties of the carcinomas remain unchanged in the majority of cases. Predictive for the chemosensitivity of tumours are a high nuclear grade, overexpression of Her-2-neu, lack of estrogen receptor expression and lymph node metastases.

Early in 2000 an interlaboratory trial on immunohistochemistry was held in Germany in which 172 pathologists took part. Each pathologist received one HE stained and five unstained slides of five different tumors to reach a diagnosis based on immunohistochemical stains. Additionally, the diagnosis-independent staining quality was assessed by using a multi-tissue block. Altogether, 828 diagnoses were made, among which 57% (468) were correct. The individual steps of immunohistochemistry (tentative morphological diagnosis, choice of primary antibodies, technical staining quality, conclusions from the diagnosis and rendering a final diagnosis) were assessed independently. Although each of these steps was correlated to the correct final diagnosis, in the multivariate analysis only the tentative diagnosis, choice of primary antibodies and the conclusions drawn from individual stains were independent factors to reach the correct final diagnosis. In the diagnostic part of the interlaboratory trial, the technical quality of the immunostaining was not an independent variable to reach a correct diagnosis. In contrast, the results of the multi-tissue block proved that the immunohistochemical staining quality has to be standardized to reach reproducible results in defining the estrogen receptor expression as a basis for therapeutic decisions.

The diagnosis of chronic eosinophilic leukemia (CEL) is based on the evidence of an autonomous, clonal proliferation of eosinophilic precursors and the exclusion of other myeloid neoplasms with eosinophilia. Histopathological evaluations of bone marrow are rare, and reliable data on the frequency of CEL do not yet exist. A total of 100 cases characterized by eosinophilia/=1.5x10(9)/l blood for more than 6 months were evaluated. In 87 cases, the eosinophilia turned out to be secondary and a reactive genesis was likely, but not proven in 3 further cases. Idiopathic hypereosinophilic syndrome was diagnosed in three cases. The diagnosis CEL was considered in four out of a total of seven cases with a myeloid neoplasia and all four disorders showed an abnormal karyotype. However, only one of them could be classified as CEL. We conclude that CEL is a rare disease concerning only a minority of cases with chronic eosinophilia.

Although modern imaging can predict the diagnosis of the vast majority of liver neoplasms, liver biopsy remains the safest, most accurate and most economical diagnostic gold standard for therapeutic implications. Refined preparation techniques using fine-needle biopsy lead to the correct diagnosis by conventional staining in most cases. Metastases and rare mesenchymal liver tumors that mimic primary hepatocellular tumors morphologically can be distinguished by use of a panel of antibodies in immunohistochemistry. Precursors of hepatocellular carcinoma (HCC) remain difficult to categorize in small biopsy specimens. Differentiation of HCC from regenerative nodules and liver cell adenomas can be achieved by molecular techniques applicable to formalin-fixed and paraffin-embedded tissue (FISH or ISH). The grading and staging of resected malignant liver neoplasms according the pTNM system still have the most important prognostic impact, but screening of changes in the cell cycle by immunohistochemistry and application of molecular techniques may prove to have prognostic value in the near future.