Midostaurin: a magic bullet that blocks mast cell expansion and activation.

Clinically relevant features in patients with systemic mastocytosis (SM) include the cosmetic burden of lesional skin, mediator-related symptoms, and organ damage resulting from mast cell (MC) infiltration in advanced forms of SM. Regardless of the SM variant, expansion of neoplastic MC in the skin and other organs is triggered by mutant forms of KIT, the most prevalent being D816V. Activation of MC with subsequent release of chemical mediators is often caused by IgE-dependent mechanisms in these patients. Midostaurin, also known as PKC412, blocks the kinase activity of wild-type KIT and KIT D816V, counteracts KIT-dependent growth of neoplastic MC, and inhibits IgE-dependent mediator secretion. Based on this activity-profile, the drug has been used for treatment of patients with advanced SM. Indeed, encouraging results have been obtained with the drug in a recent multi-center phase II trial in patients with advanced SM, with an overall response rate of 60% and a substantial decrease in the burden of neoplastic MC in various organs. Moreover, midostaurin improved the overall survival and relapse-free survival in patients with advanced SM compared with historical controls. In addition, midostaurin was found to improve mediator-related symptoms and quality of life, suggesting that the drug may also be useful in patients with indolent SM suffering from mediator-related symptoms resistant to conventional therapies or those with MC activation syndromes. Ongoing and future studies will determine the actual value of midostaurin-induced MC depletion and MC deactivation in these additional indications.

Refined diagnostic criteria and classification of mast cell leukemia (MCL) and myelomastocytic leukemia (MML): a consensus proposal.

Mast cell leukemia (MCL), the leukemic manifestation of systemic mastocytosis (SM), is characterized by leukemic expansion of immature mast cells (MCs) in the bone marrow (BM) and other internal organs; and a poor prognosis. In a subset of patients, circulating MCs are detectable. A major differential diagnosis to MCL is myelomastocytic leukemia (MML). Although criteria for both MCL and MML have been published, several questions remain concerning terminologies and subvariants. To discuss open issues, the EU/US-consensus group and the European Competence Network on Mastocytosis (ECNM) launched a series of meetings and workshops in 2011-2013. Resulting discussions and outcomes are provided in this article. The group recommends that MML be recognized as a distinct condition defined by mastocytic differentiation in advanced myeloid neoplasms without evidence of SM. The group also proposes that MCL be divided into acute MCL and chronic MCL, based on the presence or absence of C-Findings. In addition, a primary (de novo) form of MCL should be separated from secondary MCL that typically develops in the presence of a known antecedent MC neoplasm, usually aggressive SM (ASM) or MC sarcoma. For MCL, an imminent prephase is also proposed. This prephase represents ASM with rapid progression and 5%-19% MCs in BM smears, which is generally accepted to be of prognostic significance. We recommend that this condition be termed ASM in transformation to MCL (ASM-t). The refined classification of MCL fits within and extends the current WHO classification; and should improve prognostication and patient selection in practice as well as in clinical trials.

Predictors of clinical effectiveness of Hymenoptera venom immunotherapy.

BACKGROUND: Treatment failure during venom immunotherapy (VIT) may be associated with a variety of risk factors, of which the relative importance is unknown. OBJECTIVE: Our aim was to evaluate the association of baseline serum tryptase concentration (BTC), mastocytosis in the skin (MIS) and of other parameters with the frequency of objective systemic reactions during in-hospital sting challenge (SC). METHODS: In this observational retrospective study, we enrolled 1532 patients (1609 cases due to double SC) with established honeybee or vespid venom allergy who had undergone VIT and a subsequent SC. Data were collected on various putative risk factors. Adult-onset MIS and/or a BTC > 20.0 µg/L was defined as clinical indicators of systemic mastocytosis. Relative rates were calculated with logistic regression models. RESULTS: Ninety-eight patients (6.4%) presented with MIS and/or BTC > 20.0 µg/L. 104 cases (6.5%) developed objective generalized symptoms during SC. In the absence of MIS, a BTC ≤ 20 µg/L did not increase the risk for VIT failure. The most important factors associated with a worse outcome were ACE inhibitor medication (OR 5.24, 95% CI 1.83-13.00, P < 0.001), honeybee venom allergy (OR 5.09, 95% CI 3.17-8.15, P < 0.001), systemic allergic reaction during VIT (OR 3.07, 95% CI 1.79-5.14, P < 0.001), and a substantial likelihood to suffer from SM (OR 2.74, 95% CI 1.37-5.22, P = 0.003), whereas a double VIT (OR 0.51, 95% CI 0.27-0.90, P = 0.027) and a longer duration of therapy (OR 0.68 per treatment month, 95% CI 0.50-0.93, P = 0.017) reduced the failure rate. CONCLUSION: The magnitude of therapeutic success correlates with type of venom, duration of therapy, and venom dose. Adult-onset MIS and/or a BTC > 20 µg/L is a significant, albeit not the strongest determinant for VIT failure. According to its odds ratio, ACE inhibitor therapy appears to be associated with the highest risk for VIT failure.

Proposed diagnostic algorithm for patients with suspected mastocytosis: a proposal of the European Competence Network on Mastocytosis.

Mastocytosis is an emerging differential diagnosis in patients with more or less specific mediator-related symptoms. In some of these patients, typical skin lesions are found and the diagnosis of mastocytosis can be established. In other cases, however, skin lesions are absent, which represents a diagnostic challenge. In the light of this unmet need, we developed a diagnostic algorithm for patients with suspected mastocytosis. In adult patients with typical lesions of mastocytosis in the skin, a bone marrow (BM) biopsy should be considered, regardless of the basal serum tryptase concentration. In adults without skin lesions who suffer from mediator-related or other typical symptoms, the basal tryptase level is an important parameter. In those with a slightly increased tryptase level, additional investigations, including a sensitive KIT mutation analysis of blood leucocytes or measurement of urinary histamine metabolites, may be helpful. In adult patients in whom (i) KIT D816V is detected and/or (ii) the basal serum tryptase level is clearly increased (>25-30 ng/ml) and/or (iii) other clinical or laboratory features suggest the presence of 'occult' mastocytosis or another haematologic neoplasm, a BM investigation is recommended. In the absence of KIT D816V and other signs or symptoms of mastocytosis or another haematopoietic disease, no BM investigation is required, but the clinical course and tryptase levels are monitored in the follow-up. In paediatric patients, a BM investigation is usually not required, even if the tryptase level is increased. Although validation is required, it can be expected that the algorithm proposed herein will facilitate the management of patients with suspected mastocytosis and help avoid unnecessary referrals and investigations.

Prognostic impact of blast cell counts in dysplastic bone marrow disorders (MDS and CMML I) with concomitant fibrosis.

In a retrospective study, 43 patients with dysplastic neoplasms of the bone marrow (myelodysplastic syndromes and myelodysplastic/myeloproliferative-overlap neoplasms) associated with marked (grades 2-3) fibrosis were examined. Histopathologic and morphologic findings as well as cytogenetic and molecular results were correlated with clinical endpoints. Multilineage dysplasia (34 of 43 patients, 79 %) and hypercellular bone marrow (64 %) were found in most patients. In ten of 35 patients, poor risk karyotypes according to the International Prognostic Scoring System (IPSS) were recorded. The JAK2 V617F mutation was detected in four of 30 patients (13 %), and the KIT D816V mutation was found in two of 30 patients (6 %). Patients were mainly treated with palliative drugs and best supportive care. After an observation time of 1-41 (median 21) months, ten of 43 patients (23 %) had developed a secondary acute leukemia. The median survival of all 43 patients was 21.4 months (range 1.8-88.2 months). Of all prognostic parameters examined, the blast cell count at diagnosis was found to be a most reliable and most predictive marker concerning survival and leukemia progression. This confirms previous studies in dysplastic bone marrow neoplasms without fibrosis.

Evaluation of mast cell activation syndromes: impact of pathology and immunohistology.

Mast cell activation syndromes (MCAS) are clinically defined disease states with a largely unknown morphological background. Since mastocytosis may be associated with MCAS, it is crucial in every patient to document or exclude mastocytosis by appropriate histological, molecular, and serological investigations of tissues/organs that are commonly involved in mastocytosis like skin, mucosa of the gastrointestinal tract and bone marrow. Accordingly, histopathological investigation including immunohistological stains is crucial to reach the final diagnosis in such patients and to classify MCAS into primary MCAS, which can present with or without evidence of overt mastocytosis, or secondary MCAS, where an underlying disease with or without tissue inflammation is detected. Cases without evidence of mastocytosis, monoclonal mast cells, or any underlying disease should be termed idiopathic MCAS. When the activating point mutant KIT D816V is detectable but criteria for diagnosis of mastocytosis are not completely met, a so-called (mono)clonal MCAS as a subvariant of primary MCAS should be diagnosed.

[Mastocytosis and eosinophilic leukemia: diagnostics and classification]. / Mastozytosen und myeloische Neoplasien mit Eosinophilie: Diagnostik und Klassifikation.

Mastocytosis and myeloid eosinophilic neoplasms are rare diseases of the bone marrow and are often a diagnostic challenge for hematopathologists. In mastocytosis, compact mast cell infiltrates represent the main diagnostic criterion and for myeloid eosinophilic neoplasms, eosinophilic granulocytes dominate the histological picture. Both disease groups include phenotypically and prognostically very different entities which are each defined by WHO criteria. For systemic mastocytosis (SM), a differentiation between indolent and aggressive or even leukemic forms is of prognostic importance. In indolent variants of SM, a local and/or systemic, usually reactive increase in eosinophilic granulocytes (SM-eo) is often observed. In contrast, an increase in neoplastic eosinophils is often observed in advanced SM, predominantly in diseases designated SM with associated non-mastocytic hematological neoplasms (SM-AHNMD), e.g. in SM with chronic eosinophilic leukemia (SM-CEL). Apart from mastocytoses, immunophenotypically aberrant tissue mast cells are only observed in certain rare forms of myeloid neoplasms with eosinophilia, in particular in myeloproliferative neoplasms (MPN-eo) with cytogenic anomalies in the platelet-derived growth factor receptor (PDGFR). The World Health Organization (WHO) classification of eosinophilic leukemias, however, fulfils the morphological and clinical requirements in a limited way only and needs an update.

[HPV-associated squamous cell carcinogenesis]. / HPV-assoziierte Plattenepithelkarzinogenese.

About 7-8% of all human cancers are thought to be related to infections with high-risk (HR) human papilloma virus (HPV). Besides cervical cancer, especially squamous cell carcinomas of the anogenital and oropharyngeal regions are associated with HR-HPV. Transmission of HPV is due to sexual activity. Harald zur Hausen was awarded in 2008 with the Nobel price in medicine for the establishment of a causal link between certain HPV infections and cervical cancer. Meanwhile potent prophylactic vaccines are available to prevent infections with HPV-16 and HPV-18, the two most frequently observed HR HPV types worldwide. On molecular grounds a persistent HPV infection is the central risk factor for the development of HPV-associated neoplasias. Continued expression of the viral E6 and E7 oncogenes disrupts cell cycle control mechanisms in infected cells, thereby gaining limitless proliferative capacity and resistance against apoptotic signals. However acquisition of mutations and genomic instability might cause malignant transformation in these cells.

Differential diagnoses of systemic mastocytosis in routinely processed bone marrow biopsy specimens: a review.

Diagnosis of systemic mastocytosis (SM) is mainly based on the morphological demonstration of compact mast cell infiltrates in various tissue sites. In almost all patients such infiltrates are detected in the bone marrow. Reliable immunohistochemical markers for the diagnosis and grading of SM have been established, but various differential diagnoses including myeloproliferative neoplasms, basophilic and eosinophilic leukemias may be very difficult to delineate. Even more challenging is the recognition of hematological neoplasms with signs of mast cell differentiation but not fulfilling diagnostic criteria for SM, especially the rare myelomastocytic leukemia. It is also important to separate the reactive state of mast cell hyperplasia from indolent variants of SM, especially those with a very low degree of bone marrow infiltration and absence of compact mast cell infiltrates. When the lymphocytic component of the SM infiltrate is very prominent, SM may be confused with an indolent lymphoma, especially lymphoplasmacytic lymphoma which almost always shows a marked reactive increase in mast cells. In aggressive and leukemic variants of SM, mast cells may be very atypical and devoid of metachromatic granules. This hypogranulation can be regarded as cellular atypia and may lead to the misdiagnosis aspect of monocytic leukemia or histiocytic neoplasm. Regarding immunohistochemical anomalies, mast cells in aggressive and leukemic SM have been found to express CD30 (Ki1-antigen). Thus, anaplastic large cell lymphoma or Hodgkin's disease may first be considered rather than SM. There is increasing evidence that most patients with long-standing adult-type urticaria pigmentosa-like skin lesions have in fact indolent SM. Therefore, such skin lesions are an important clue to the correct diagnosis in these patients. However, in aggressive or leukemic SM skin lesions are usually absent and then the correct diagnosis relies on an appropriate investigation of bone marrow biopsy specimens using both SM-related immunohistochemical markers (tryptase, KIT, CD25, CD30) but also markers excluding potential differential diagnoses. Investigation for presence of the activating KIT point mutation D816V is very helpful to establish a correct diagnosis of SM in all the difficult cases exhibiting a low degree of bone marrow infiltration or puzzling morphological findings.

Microsatellite instability and HPV genotype in Polish women with cervical cancer.

INTRODUCTION: Human papillomaviruses (HPVs) are associated with anogenital cancer. Little is known about the prevalence of microsatellite instability (MSI) in cervical cancer. The aim of this study was to investigate the incidence of microsatellite instability in cervical cancer and to see whether there is a relation between MSI, HPV and clinicopathological characteristics in the study population. RESULTS: Using three assays (pU1M/2R, GP5+/6+ and E6-nested multiplex PCR) HPV was detected in 110 out of 113 patients with histologically confirmed cervical cancer. The presence of MSI was investigated in 95 of the 113 cases using seven microsatellite loci. In total, 12 out of the 95 patients (12.6%) showed MSI. None of clinicopathological parameters showed a significant difference between microsatellite stable and MSI cases. CONCLUSION: In this population of Polish cervical cancer patients, 12.6% showed microsatellite instability. There was no correlation between MSI positivity and clinicopathological parameters and/or survival.

[Human papillomavirus infection. Pathology and molecular pathology]. / Die Infektion mit humanen Papillomaviren. Pathologie und Molekularpathologie.

Cervical cancer is the second most frequent female malignoma worldwide and accounts for about 500,000 cases every year. The peak incidence lies between 35 and 55 years of age. Persistent infections with a group of 15 so-called high-risk human papillomaviruses (HR-HPV) are the cause of cervical carcinogenesis of squamous cell carcinomas and for most of the adenocarcinomas. The transforming potential of HR-HPVs is based on the interaction of viral oncogene products E6 and E7 with the cellular tumor suppressor proteins p53 and pRB. The resulting loss of cell cycle control sets the basis for additional, as yet only incompletely discovered, genetic and epigenetic changes, finally leading to invasive growth. Preneoplastic changes, cervical intraepithelial neoplasias, can be identified morphologically, thus allowing for therapeutic interventions. Since November 2007, the Ständige Impfkommission, the German standing committee on immunizations, has recommended the prophylactic use of vaccines against the two most frequent HR-HPV genotypes, HPV-16 and HPV-18, in women age 12-17 years before first sexual intercourse. In addition to cervical cancer, HPV infections are responsible for the development of genital warts (condyloma) and a number of vaginal, vulvar, and anal intraepithelial neoplasias. HPV infections are usually transmitted sexually.

Drug-induced inhibition of phosphorylation of STAT5 overrides drug resistance in neoplastic mast cells.

Systemic mastocytosis (SM) is a mast cell (MC) neoplasm with complex pathology and a variable clinical course. In aggressive SM (ASM) and MC leukemia (MCL), responses to conventional drugs are poor and the prognosis is dismal. R763 is a multi-kinase inhibitor that blocks the activity of Aurora-kinase-A/B, ABL1, AKT and FLT3. We examined the effects of R763 on proliferation and survival of neoplastic MC. R763 produced dose-dependent inhibition of proliferation in the human MC lines HMC-1.1 (IC50 5-50 nM), HMC-1.2 (IC50 1-10 nM), ROSAKIT WT (IC50 1-10 nM), ROSAKIT D816V (IC50 50-500 nM) and MCPV-1.1 (IC50 100-1000 nM). Moreover, R763 induced growth inhibition in primary neoplastic MC in patients with ASM and MCL. Growth-inhibitory effects of R763 were accompanied by signs of apoptosis and a G2/M cell cycle arrest. R763 also inhibited phosphorylation of KIT, BTK, AKT and STAT5 in neoplastic MC. The most sensitive target appeared to be STAT5. In fact, tyrosine phosphorylation of STAT5 was inhibited by R763 at 10 nM. At this low concentration, R763 produced synergistic growth-inhibitory effects on neoplastic MC when combined with midostaurin or dasatinib. Together, R763 is a novel promising multi-kinase inhibitor that blocks STAT5 activation and thereby overrides drug-resistance in neoplastic MC.

Management of late recurrence of a low-grade endometrial stromal sarcoma (LGESS): treatment with letrozole.

Low grade endometrial stromal sarcoma (LGESS) is a rare disease. LGESS usually expresses steroidal receptors and is regarded to be hormone-sensitive. Due to the rarity of the tumor, only few case series have been published so far. Here, we report the case of a 36-year-old woman who underwent an abdominal hysterectomy with bilateral salpingo-oophorectomy and adjuvant radiotherapy for a G1 LGESS in 1991. Twelve years later she presented to us with pelvic and peritoneal masses. The patient was treated with letrozole achieving a partial response which is lasting 39 months. Treatment is ongoing. Aromatase inhibitors represent an interesting treatment option for LGESS.

Increased translocator protein (TSPO) mRNA levels in colon but not in rectum carcinoma.

BACKGROUND: The peripheral-type benzodiazepine receptor or translocator protein (TSPO) is an 18-kDa protein involved in cell proliferation and apoptosis. TSPO was shown to be overexpressed in malignant tumors and cancer cell lines, correlating with enhanced malignant behavior. The present study analyzed the role of TSPO in patients with colorectal carcinomas. METHODS: Tumor tissues and corresponding normal mucosa from 55 patients who underwent resection for colorectal carcinomas were analyzed for TSPO expression in correlation to GAPDH expression(glyceraldehyde-3-phosphate dehydrogenase) using a multiplex RT-PCR assay. RESULTS: TSPO was overexpressed in 67% of the tumors in comparison to corresponding normal mucosa, and positivity as well as expression levels in colon carcinomas were significantly higher than in the rectum carcinomas. In contrast, TSPO expression was not different in intermediate versus high-grade tumors or in lymph node-positive versus -negative patients. CONCLUSION: The differences in TSPO expression between colon and rectum carcinoma may imply that these tumors are of different biological behavior.

[The interdisciplinary approach to improve treatment quality of prostate cancer. Optimized nerve sparing in radical prostatectomy]. / Interdisziplinäre Untersuchungen zur Verbesserung der Behandlungsqualität des Prostatakarzinoms. Optimierung des Nervenerhalts bei radikaler Prostatektomie.

BACKGROUND: After sufficient oncological treatment of prostate cancer the life quality becomes most important. A multi disciplinary research network aims to optimize the diagnostics and the resulting treatment of prostate cancer. METHODS: Main characteristics of the interdisciplinary cooperation are the interlocked individual projects. A major research field is investigation of the whole mounted prostate sections to study the peripheral nerves and the comparison of histological tumor locations with the MRI. Using serial sections of prostate specimens, three-dimensional computer-animated models are created illustrating the tumors histological and immunohistochemical distributions. For nodal staging, a new methodology is investigated to demonstrate single tumor cells in lymphatic tissue lysates. A retrospective evaluation of life quality including the functional outcome is performed by using questionnaire surveys. RESULTS: Anatomical studies gave new insights into the exact localizations of peripheral nerves which may lead to an improvement of the surgical approach in nerve-sparing radical prostatectomy. For the preoperative planning the MRI imaging might need a different interpretation in relation to the topographic location. Studies using molecular markers and their relation and distribution patterns gave new insights regarding interpretation of histological biopsy results concerning the tumor extension. Numerical quantification of tumor cells in each lymph node demonstrated micro metastases in histological negative nodes contributing to the nodal staging. A close connection of the nerve-sparing technique was demonstrated with quality of life aspects and functional results. CONCLUSION: An interdisciplinary approach is mandatory for translational prostate cancer research. As a result, individualized diagnostic and therapeutic approaches improve oncological results and at the same time provide the best quality of life in these patients.

Proposed diagnostic criteria and classification of basophilic leukemias and related disorders.

Basophils form a distinct cell lineage within the hematopoietic cell family. In various myeloid neoplasms, including chronic myeloid leukemia, basophilia is frequently seen. Acute and chronic basophilic leukemias, albeit rare, have also been described. However, no generally accepted criteria and classification of basophilic leukemias have been presented to date. To address this unmet need, a series of Working Conferences and other meetings were organized between March 2015 and March 2016. The current article provides a summary of consensus statements from these meetings, together with proposed criteria to delineate acute basophilic leukemia (ABL) from chronic basophilic leukemia (CBL) and primary forms of the disease where no preceding myeloid malignancy is detected, from the more common 'secondary' variants. Moreover, the term hyperbasophilia (HB) is proposed for cases with a persistent peripheral basophil count ⩾1000 per µl of blood. This condition, HB, is highly indicative of the presence of an underlying myeloid neoplasm. Therefore, HB is an important checkpoint in the diagnostic algorithm and requires a detailed hematologic investigation. In these patients, an underlying myeloid malignancy is often found and is then labeled with the appendix -baso, whereas primary cases of ABL or CBL are very rare. The criteria and classification proposed in this article should facilitate the diagnosis and management of patients with unexplained basophilia and basophil neoplasms in routine practice, and in clinical studies.

An unusual case of systemic mastocytosis associated with chronic lymphocytic leukaemia (SM-CLL).

AIMS: Whereas focal accumulations of reactive lymphocytes around mast cell (MC) infiltrates are often seen in indolent systemic mastocytosis (ISM) involving the bone marrow, an association of systemic mastocytosis (SM) with malignant lymphoma/lymphatic leukaemia is very rare. This report contributes to the differential diagnosis of ISM by demonstrating that such lymphocytic aggregates may be neoplastic. METHODS: Biopsy specimens (bone marrow and gastrointestinal mucosa) of a 69 year old woman with mild blood lymphocytosis and a history of urticaria pigmentosa-like skin lesions that had disappeared a few years earlier, were investigated immunohistochemically using antibodies against CD3, CD5, CD20, CD23, CD25, CD34, CD117, chymase, and tryptase. Rearrangements of the IgH and TCRy genes were studied by seminested PCR. Mutation analysis of c-kit was performed by melting point analysis of nested PCR using amplified DNA from pooled microdissected single cells (MC and B cells) of both sites. RESULTS: The histomorphological features of the bone marrow corresponded to that of ISM with multifocal accumulations of MC surrounded by clusters of lymphocytes of mature appearance. However, these lymphocytes revealed an aberrant immunophenotype with coexpression of CD5, CD20, and CD23, thus enabling the final diagnosis of SM with an associated clonal haematological non-MC lineage disease, in particular SM with associated B cell chronic lymphocytic leukaemia (SM-CLL). Monoclonality for both ISM and B-CLL could be confirmed by demonstrating the typical activating c-kit point mutation D816V in bone marrow MC, and a monoclonal IgH rearrangement in bone marrow B cells. CONCLUSIONS: Usually, focal accumulations of lymphocytes around MC infiltrates in the bone marrow of patients with SM are reactive in nature (lymphocytosis). However, a low grade malignant lymphoma should also be included in the differential diagnosis. We describe here the first case, to our knowledge, with synchronous diagnosis of SM and associated B-CLL. This diagnosis could only be established by application of appropriate immunohistochemical and molecular techniques, as the bone marrow histology on first investigation resembled that of typical ISM.

"Occult" mastocytosis with activating c-kit point mutation evolving into systemic mastocytosis associated with plasma cell myeloma and secondary amyloidosis.

A case of a 70-year-old man presenting with exsudative enteropathy due to light-chain-associated amyloidosis is reported. The diagnosis of systemic mastocytosis associated with IgG/lambda plasma cell myeloma and secondary generalised amyloidosis was carried out by morphological evaluation of bone marrow biopsy. The c-kit point mutation D816Y was detected by molecular analysis. Two years before, a cystadenolymphoma of the left parotid gland had been removed. A moderate increase of loosely scattered spindle-shaped mast cells, a subpopulation of them expressing CD25, an antigen that is not expressed by normal or reactive mast cells, was shown by retrospective analysis carried out on an intraparotideal lymph node. The c-kit mutation D816Y was shown by the molecular analysis of the lymph node. In summary, the notion that systemic mastocytosis may very rarely be associated with B cell neoplasms and that neoplastic mast cell infiltrates may be obscured because of only a minimal increase of atypical mast cells, which are outnumbered by other non-neoplastic cells in the same tissue, is supported by this case. This finding was preliminarily termed "occult" mastocytosis.

The tryptase positive compact round cell infiltrate of the bone marrow (TROCI-BM): a novel histopathological finding requiring the application of lineage specific markers.

AIMS: Compact tryptase-positive round cell infiltrates of the bone marrow (TROCI-BM) are very rare histopathological findings and may pose challenging problems with regard to the cell type involved (either mast cells or basophilic granulocytes) and the exact diagnosis. METHODS: A selected panel of immunohistochemical markers against mast cell and basophil related antigens, including CD25, CD34, CD117/Kit, and the 2D7 antigen (which is found only in basophilic granulocytes) on a total of 410 routinely processed bone marrow biopsy specimens (including 88 cases of systemic mastocytosis (SM), 20 cases of chronic myeloid leukaemia (CML), 92 cases of myeloid neoplasms other than CML, and 210 controls with normal/reactive bone marrows). RESULTS: In total, 17 cases with TROCI-BM could be identified: 11 SM (including two cases of well-differentiated SM and two mast cell leukaemias; MCL), 2 myelomastocytic leukaemia (MML), 2 CML with excess of basophils (secondary basophilic leukaemia (CMLba)), and 2 tryptase positive acute myeloid leukaemia (AML). Regarding the cell types involved, TROCI-BM cells were found to express CD117/Kit in all cases of SM and MCL. In MML and tryptase postitive AML, TROCI-BM cells were found to coexpress CD34 and Kit. The basophil specific antigen 2D7 was only detected in CD34/Kit negative TROCI-BM cells in two patients with CMLba. The activating point mutation D816V was detected in 8/11 patients with SM but not in any of the other haematological malignancies. CONCLUSIONS: In summary, a total of six rare myeloid neoplasms may present with a novel immunohistochemical phenomenon tentatively termed TROCI-BM.

Simplified detection of microsatellite instability in colorectal cancer without the need for corresponding germline DNA analysis.

A panel of five quasimonomorphic mononucleotide repeats that dispenses with the need to analyse corresponding germline DNA was proposed by Suraweera et al for the detection of high-frequency microsatellite instability (MSI) in colorectal cancer. Using this panel, a simplified and a more sensitive (compared with the original) algorithm (p<0.05) was developed to define the instability of each repeat by assessing the morphological shape of its plot and not its absolute length. 103 cases of colorectal tumours were investigated and the results compared with those obtained by the analysis of five consensus microsatellites (Bethesda reference panel). By the proposed method, a higher specificity, but no loss of sensitivity, was found. Thus, the use of the five mononucleotide repeats in combination with the modified assessment technique simplifies the assessment of MSI, while retaining the sensitivity of the Bethesda panel for the detection of high-frequency MSI.