Fine-needle aspiration biopsy diagnosis of gastrointestinal stromal tumors using morphology, immunocytochemistry, and mutational analysis of c-kit

FLT3 K663Q is a novel AML-associated oncogenic kinase: Determination of biochemical properties and sensitivity to Sunitinib (SU11248)

Somatic mutations of FLT3 resulting in constitutive kinase activation are the most common acquired genomic abnormality found in acute myeloid leukemia (AML). The majority of these mutations are internal tandem duplications (ITD) of the juxtamembrane region (JM). In addition, a minority of cases of AML are associated with mutation of the FLT3 activation loop (AL), typically involving codons D835 and/or I836. We hypothesized that other novel mutations of FLT3 could also contribute to leukemogenesis. We genotyped 109 cases of AML and identified two novel gain-of-function mutations. The first mutation, N841 H, is similar to previously described mutations involving amino-acid substitutions of codon 841. The other novel mutation, FLT3 K663Q, is the first AML-associated gain-of-function mutation located outside the JM and AL domains. Of note, this mutation was potently inhibited by Sunitinib (SU11248), a previously described FLT3 kinase inhibitor. Sunitinib reduced the proliferation and induced apoptosis of transformed Ba/F3 cells expressing FLT3 K663Q. The potency of Sunitinib against FLT3 K663Q was similar to its potency against FLT3 ITD mutations. We conclude that FLT3 mutations in AML can involve novel regions of the TK1. Future studies are needed to define the incidence and prognostic significance of FLT3 mutations outside the well-established JM and AL regions.

Imaging, morphologic, and immunohistochemical correlation in gastrointestinal stromal tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) recently have been distinguished morphologically, immunohistochemically, and genetically from other gastrointestinal-tract spindle cell neoplasms. The objective of this study was to correlate clinical and imaging findings with morphology and immunohistochemistry to diagnose GISTs and to differentiate them from other spindle cell lesions in the gastrointestinal tract.

METHODS

The authors reviewed 9 patients who had tumors that were diagnosed as GIST by image-guided and endosonographic-guided fine-needle aspiration (FNA) with or without core biopsy (7 stomach tumors and 2 intraabdominal tumors). The male:female ratio was 3:6, and the patients ranged in age from 38 years to 80 years. Onsite evaluation, preliminary cytologic evaluation, and immunohistochemistry were provided for 6 patients. Immunostains were performed, depending on sample size, on aspirates and/or core biopsies.

RESULTS

On imaging studies, most tumors were smooth and homogenous, consistent with GIST. Tumors ranged in size from 1.8 cm to 22 cm. The largest neoplasm showed solid/cystic and necrotic components. Aspirates consisted of spindle cell, neoplastic proliferation arranged in fascicles that exhibited focal, nuclear palisading; indistinct, cytoplasmic borders; and no significant atypia or mitosis. Focal epithelioid changes or cytologic atypia and mitoses were observed in 2 tumors. Immunostains revealed tumor expression of CD117 and/or CD34 in 5 of 6 tumors, expression of actin in 3 of 6 tumors, and expression of desmin in 1 of 6 tumors. All tumors were diagnosed as GIST (or consistent with GIST for tumors that lacked immunochemical analysis). Five patients underwent surgical excision, and the GIST diagnosis was confirmed in 3 patients, whereas 1 tumor proved to be neurofibroma, and another tumor was leiomyoma. No surgical follow-up was available for the remaining 4 patients, who had imaging and morphologic findings consistent with GIST.

CONCLUSIONS

In the setting of consistent clinical and radiologic findings, the combined use of cytomorphology and immunohistochemistry on FNA and/or core biopsy in most instances provides a reliable pathologic diagnosis of GIST. The need of sufficient material for performing ancillary studies and the usual impossibility of excluding malignancy are limitations of FNA cytology of GIST.

Review of endoscopic ultrasound-guided fine-needle aspiration cytology

This review, based on the Hennepin County Medical Center experience and review of the literature, vastly covers the up-to-date role of endoscopic ultrasonography (EUS) and EUS-guided fine-needle aspiration (FNA) in evaluating tumorous lesions of the gastrointestinal tract and adjacent organs. Emphasis is given to the tumoral and nodal staging of esophageal, pulmonary, and pancreatic cancer. This review also discusses technical, pathological, and gastroenterologic aspects and the role of the pathologist and endosonographer in the evaluation of these lesions, as well as the corresponding FNA cytology and differential diagnosis.

Gastrointestinal stromal tumor (GIST)

Gastrointestinal stromal tumors (GISTs), the most common nonepithelial neoplasms of the gastrointestinal (GI) tract, occur most commonly in the stomach. These neoplasms were previously classified as smooth muscle tumors, but it has become apparent that they represent distinct clinicopathologic entities. All GISTs should be considered as having malignant potential, although they display varying degrees of aggressiveness. Although usually asymptomatic, large GISTs may present with pain or bleeding. Definitive diagnosis is made by immunohistochemical staining of the tissue for CD117, also known as KIT protein, a cell membrane receptor with tyrosine kinase activity. Size and mitotic activity are predictive of malignant behavior. Primary treatment for GISTs with high malignant potential is surgical resection. Specific therapy targeting the KIT receptor with imatinib has resulted in improved outcomes for patients with unresectable, metastatic, and recurrent disease.

The utility of fine-needle aspiration in the diagnosis of gastrointestinal stromal tumors: a cytomorphologic and immunohistochemical analysis with emphasis on malignant tumors

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal neoplasms of the tubular gut and mesentery. Fine-needle aspiration biopsy (FNAB) currently is a useful tool in the diagnosis of GIST because of various mutations of the KIT protooncogene that are recognized as characteristic of these tumors. Despite such advances, the malignant potential of GIST remains variable, and few studies have reported their findings in patients with malignant GIST. Therefore, in the current study, the authors have reported their experience with FNAB as a diagnostic tool in one of the largest series of malignant GISTs and have analyzed the cytomorphologic features of the tumors relative to their clinical behavior to determine which, if any, cytologic features are indicators of malignancy.

METHODS

All patients with histologically confirmed GIST who were diagnosed by image-guided FNAB and confirmed with positive CD117 staining from 1998 to 2003 were included in the study. All tumors were reviewed for various cytomorphologic features. For study purposes, the patients were divided into two groups: Group A included all patients with malignant tumors, defined as those with metastatic disease or recurrent disease after adequate surgery with or without chemotherapy; Group B included all other patients.

RESULTS

In total, 26 tumors from 23 patients (8 males and 15 females) with a mean age of 60.9 years were available for review. There were 14 primary tumors, 7 metastases (to the liver), and 5 recurrences. Twenty-one tumors were unequivocally malignant and were placed into Group A; the remaining 5 tumors were placed into Group B. The tumors in both groups were characterized by spindled or epithelioid cells with minimal nuclear atypia or pleomorphism and a moderate amount of cytoplasm. None of the cytologic features that were evaluated could distinguish reliably between benign tumors and malignant tumors, as expected. However, on cytologic examination, all tumors that demonstrated mitoses (n = 7 tumors) and/or pretreatment necrosis (n = 3 tumors) were identified as malignant.

CONCLUSIONS

FNAB remains a reliable method for the diagnosis of GIST. Immunohistochemical staining of cytologic material with CD117 has been reliable in establishing this diagnosis by FNAB, provided adequate tissue is procured. In the current study, the presence of necrosis or mitoses in cytologic specimens was correlated with a diagnosis of malignant GIST.

Fine needle aspiration biopsy of gastrointestinal stromal tumor presenting as an umbilical mass (Sister Mary Joseph's Nodule)

The Sister Mary Joseph (SMJ) nodule is a clinical sign of metastatic cancer involving the umbilicus. The vast majority of these instances represent adenocarcinomas arising from ovarian or colorectal primaries. We present a patient who presented with ascites and the SMJ lesion that turned out to be a metastatic gastrointestinal stromal tumor after fine needle aspiration biopsy was performed. The lesion was subsequently histologically confirmed. Gastrointestinal stroma tumor involving the umbilicus is exceedingly uncommon and only rarely presents in this fashion. The cytomorphological features, differential diagnosis, and comparison with the tissue specimen are made.

Fine-needle aspiration of soft tissue leiomyosarcoma: An analysis of the most common cytologic findings and the value of ancillary techniques

This study aims to determine the diagnostic accuracy of fine-needle aspiration cytology (FNAC) of primary leiomyosarcoma (LMS) of soft tissue and to review diagnostic criteria and adjunctive methods, which can contribute to a confident diagnosis. We evaluated the preoperative FNAC in 89 patients with primary LMS for the following: cytomorphology and correspondence of FNA to histological features of excised tumors and clinical data. In addition, the utility of adjunctive techniques was analyzed and other spindle-cell lesions in the differential diagnoses were discussed. An unequivocal, malignant diagnosis was rendered by FNAC in 78 cases; 74 tumors were diagnosed as sarcoma, of which 31 as LMS or suspicion of LMS. In addition, three smears were labeled as malignant tumor, one as carcinoma metastasis, and three as neurilemmoma. Seven aspirates were inconclusive and one insufficient. On reevaluation, the diagnostic smears in most cases contained tumor cell fascicles with an admixture of dispersed cells or stripped nuclei. The most common cells were spindle cells with elongated, blunt-ended, segmented or fusiform nuclei, and round/polygonal cells, often with rounded or indented nuclei. In addition, 51 cases showed pleomorphic, often multinucleated cells. Osteoclasts, intranuclear vacuoles, and mitoses occurred in 14, 47, and 27 cases, respectively. Thus, most high-grade LMSs have cytologic features that allow diagnosis of sarcoma. Ancillary studies can confirm the diagnosis of LMS and help in the correct interpretation of predominant spindle-cell or epitheloid-cell smears resembling neurilemoma or carcinoma, respectively.

Gastrointestinal stromal tumours: an update

Recently, there has been intense interest in the study of gastrointestinal stromal tumour (GIST); one might call it a virtual GIST revolution. This is due largely to the realization that most GISTs express KIT and harbour activating c-KIT (KIT) or platelet-derived growth factor receptor-alpha (PDGFRA) receptor tyrosine kinase mutations that can be targeted by small molecule pharmacological inhibitors. Pathologists have benefited greatly from this revolution, mainly in the form of an improved ability to classify GISTs and, even more recently, in understanding the molecular underpinnings that underlie many fascinating clinical and pathological correlations. It is the purpose of this review to summarize recent developments in GIST classification and the molecular pathogenesis of GIST.

Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNAB): past, present, and future

Endoscopic ultrasound (EUS) is a combination of endoscopy and intraluminal ultrasonography. EUS also enables ultrasonographic images of high resolution to be obtained. However, whether a lesion is malignant or benign cannot be diagnosed solely from the findings of EUS. Endoscopic ultrasound-guided fine-needle aspiration biopsy (EUS-FNAB) was developed to enhance the diagnostic capabilities of EUS by providing additional pathological findings. Though more than 10 years have passed since EUS-FNAB was first used for pancreatic disease, EUS FNAB has not been widely accepted in Japan. This may be due to the technical difficulties, relatively low sensitivity for the detection of malignancies, and Japanese gastroenterologists' and surgeons' inherent conservative way of thinking. We describe here a short history of EUS-FNAB, with details of technical tips, current indications and contraindications, diagnostic accuracy, and complications. The clinical utility of EUS-FNAB has been gradually understood and EUS-FNAB procedures have been increasing in number in Japan. So in the near future, EUS followed by EUS-FNAB will be routinely performed in the same manner as gastrointestinal endoscopy, followed by biopsy under direct vision. Also, therapeutic EUS procedures, such as EUS-guided celiac plexus neurolysis, pancreatic tumor ablation, drainage of pancreatic pseudocysts, and the development of an anastomosis may become feasible as less invasive and safer techniques than those used at present.

Pathophysiology, diagnosis, and treatment of gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are the most common mesenchymal tumors of the gastrointestinal tract. Activating mutations of KIT or the platelet-derived growth factor receptor alpha gene (PDGFRA) have been identified in the vast majority of GISTs. The respective oncoproteins exhibit constitutive tyrosine kinase activity and promote cell growth. KIT and PDGFRA mutations are rarely found in GISTs in patients with neurofibromatosis type 1 (NF1) suggesting that the pathogenesis of GIST in NF1 patients is different from that in non-NF1 patients. Endoscopic diagnosis of GIST is usually difficult. Endoscopic ultrasonography (EUS)-guided fine-needle aspiration biopsy (EUS-FNAB) is a useful method for the diagnosis of GIST and for the detection of KIT or PDGFRA mutations. Imatinib mesylate, a tyrosine kinase inhibitor known to inhibit the activities of BCR-ABL, KIT, and PDGFR, is currently being used for the treatment of both chronic myeloid leukemia and metastatic GIST. The clinical response to imatinib therapy correlates with the types of mutations of KIT and PDGFRA, and the determination of KIT and PDGFRA mutations is useful for predicting the effect of imatinib. Resistance to imatinib after an initial response has been reported; secondary point mutations in KIT or PDGFRA that confer imatinib resistance are the most common mechanisms responsible for acquired resistance to imatinib. The continued development of target-specific therapies should increase the probability of cure in most patients with GISTs.

c-KIT mutation analysis for diagnosis of gastrointestinal stromal tumors in fine needle aspiration specimens

BACKGROUND

Gastrointestinal stromal tumors (GISTs) are a specific clinicopathologic entity characterized by activating mutations in the c-KIT gene. These mutations are associated with increased immunohistochemical staining for the c-KIT protein. Because many GISTs display a definitive response to the KIT inhibitor imatinib, accurate diagnosis of these neoplasms is of great clinical importance. GISTs are the most common mesenchymal neoplasms of the digestive tract and show lineage differentiation along the lines of the interstitial cells of Cajal. The cytomorphology of GISTs has been well described, but the cytologic features are not entirely specific and immunohistochemical staining is frequently used to confirm the diagnosis. However, KIT protein positivity established by immunohistochemistry (IHC) may be unreliable in some instances because of a small number of KIT-negative GISTs and immunohistochemical KIT positivity in some non-GIST spindle cell neoplasms of the gastrointestinal tract. Antigen retrieval may be the cause of this spurious positivity. Recently, the demonstration of KIT and PDGFRA mutations has been shown to be more reliable in establishing the diagnosis of GIST than IHC.

METHODS

High resolution amplicon melting analysis was performed in a series of eight gastrointestinal stromal tumors sampled by fine needle aspiration (FNA).

RESULTS

In five of eight cases, adequate material was obtained for mutational analysis. In four of these, mutations in the c-KIT gene were detected, and in the fifth case a mutation in the PDGFRA gene was detected.

CONCLUSIONS

It appears that high resolution amplicon melting analysis can be successfully performed on material obtained by FNA and will show either KIT for PDGFR mutations in the majority of GIST FNA specimens.

Submucosal lesions

Most of the submucosal lesions encountered on endoscopy are benign; however, the fact that some of them may be malignant considerably influences the attitude toward the whole group. This article reviews the current status of endosonography in the management of submucosal lesions and focuses on determining the risk of malignancy. The predictive value of various endoscopic ultrasonography (EUS) features and their combinations and the capabilities and limitations of EUS-guided fine needle biopsy are discussed. Other issues addressed include differentiation between extraluminal compressions and true submucosal lesions, EUS-assisted endoscopic removal of submucosal lesions, and the potential role of catheter-based endosonography in the setting of submucosal lesions. Problems related to the surveillance of patients with submucosal lesions who are not candidates for surgical treatment are outlined. An overview of the recent changes in the pathologic classification of gastrointestinal mesenchymal tumors and their impact on the role of EUS in the management of submucosal lesions is given.

Gastrointestinal stromal tumors (GISTs)

PURPOSE OF REVIEW

Gastrointestinal stromal tumors (GISTs) have recently been the subject of considerable clinical and experimental interest. This focus is based on the recognition that GISTs characteristically have uncontrolled activation of the KIT protein, a transmembrane tyrosine kinase receptor involved in cell survival, development, and proliferation. The clinical application of imatinib mesylate, a selective inhibitor of the KIT kinase activity, has provided a novel molecularly targeted therapy for these tumors. This review summarizes publications from the last year regarding these tumors.

RECENT FINDINGS

Recent studies have focused on imaging, the identification of prognostic factors and molecular events, and the role of systemic therapy in the treatment of these tumors. Emerging data suggest that the combination of endoscopic ultrasound and fine-needle aspiration analysis for KIT expression may be useful in separating these lesions from other submucosal lesions of the gastrointestinal tract. The benefits and limitations of computed tomography and positron emission tomography in identifying, staging, and evaluating the response to therapy of these lesions have been more clearly defined. Although tumor size and the number of mitoses remain the best prognostic markers, several studies reported provocative data using other markers such as Ki-67, p53, and alterations in p16. Mutational analysis of the KIT oncoprotein continues to be the subject of considerable interest in relation to both prognosis and resistance to therapy. Finally, a series of new studies have confirmed the benefits and better defined the results of therapy with imatinib mesylate. There is increasing interest in expanding the role of this agent into the adjuvant setting and in combining such therapy with reoperation for responsive disease.

SUMMARY

In the past year there have been significant developments in our understanding of GISTs and their response to therapy. Many questions remain unanswered and new issues have arisen as the benefits of imatinib mesylate therapy are revealed. There is considerable optimism that the targeted molecular approach being applied to the treatment of GISTs will serve as a model for the development of similar approaches to other more common tumors.

c-CBL is not required for leukemia induction by Bcr-Abl in mice

Bcr-Abl tyrosine kinase activity is essential for the pathogenesis of chronic myeloid leukemia (CML). A number of Bcr-Abl substrates have been identified, but it is not clear which of these substrates are required for Bcr-Abl to transform cells. The multifunctional protein c-Cbl is one of the most prominently tyrosine-phosphorylated proteins in Bcr-Abl-expressing cells. Using cell lines and mice with homozygous disruption of the c-CBL locus, we investigated the role of this protein for Bcr-Abl-driven transformation. We find that although c-Cbl(-/-) fibroblast cell lines show a deficit in Bcr-Abl transformation compared to wild-type (Wt) cells, this deficit was less pronounced in c-Cbl(-/-) B cells derived from murine bone marrow. Most importantly, in a transplantation model of CML, Bcr-Abl was capable of inducing fatal leukemia in mice in the absence of c-Cbl protein. Our results indicate that c-Cbl is dispensable for Bcr-Abl-induced leukemogenesis in mice.

Kinase mutations and imatinib response in patients with metastatic gastrointestinal stromal tumor

PURPOSE

Most gastrointestinal stromal tumors (GISTs) express constitutively activated mutant isoforms of KIT or kinase platelet-derived growth factor receptor alpha (PDGFRA) that are potential therapeutic targets for imatinib mesylate. The relationship between mutations in these kinases and clinical response to imatinib was examined in a group of patients with advanced GIST.

PATIENTS AND METHODS

GISTs from 127 patients enrolled onto a phase II clinical study of imatinib were examined for mutations of KIT or PDGFRA. Mutation types were correlated with clinical outcome.

RESULTS

Activating mutations of KIT or PDGFRA were found in 112 (88.2%) and six (4.7%) GISTs, respectively. Most KIT mutations involved exon 9 (n = 23) or exon 11 (n = 85). All KIT mutant isoforms, but only a subset of PDGFRA mutant isoforms, were sensitive to imatinib, in vitro. In patients with GISTs harboring exon 11 KIT mutations, the partial response rate (PR) was 83.5%, whereas patients with tumors containing an exon 9 KIT mutation or no detectable mutation of KIT or PDGFRA had PR rates of 47.8% (P =.0006) and 0.0% (P <.0001), respectively. Patients whose tumors contained exon 11 KIT mutations had a longer event-free and overall survival than those whose tumors expressed either exon 9 KIT mutations or had no detectable kinase mutation.

CONCLUSION

Activating mutations of KIT or PDGFRA are found in the vast majority of GISTs, and the mutational status of these oncoproteins is predictive of clinical response to imatinib. PDGFRA mutations can explain response and sensitivity to imatinib in some GISTs lacking KIT mutations.

Endoscopic ultrasonography-guided fine needle aspiration biopsy in follow-up patients with gastrointestinal stromal tumours

OBJECTIVES

Since all gastrointestinal stromal tumours (GISTs) are practically considered to be potentially malignant, they must be clinically differentiated from other submucosal tumours (SMTs). In this study, we carried out endoscopic ultrasonography-guided fine needle aspiration biopsy (EUS-FNAB) against follow-up SMTs to examine whether the method is sufficient for pathological diagnosis and analysis of c-kit mutation. The relationship between tumour growth and c-kit mutation was also examined.

METHODS

The tumour tissues were obtained by EUS-FNAB from 10 Japanese follow-up cases with SMT. Paraffin sections of tissues were used for haematoxylin and eosin staining, and for immunohistochemistry. Genomic DNA was extracted from the sections, and c-kit gene fragments of exons 9, 11, 13 and 17 were amplified by polymerase chain reaction and directly sequenced.

RESULTS

Nine SMTs were diagnosed as GIST and one was diagnosed as schwannoma by immunohistochemistry. Mutation at exon 11 was detected in six of nine GISTs, but no mutations were detected at exons 9, 13 and 17 in all GISTs. The case of schwannoma did not have any mutations at exons 9, 11, 13 and 17. Statistical significance was not observed between the average growth rate of six GISTs with the mutation and that of three GISTs without the mutation (P = 0.694).

CONCLUSIONS

EUS-FNAB against SMTs was useful for the differential diagnosis of SMT and the analysis of c-kit mutation. The c-kit mutation might not be one of the predictable markers for rapid tumour growth.

Gastrointestinal tract cytology: advancing horizons

Tide and ebb of interest in gastrointestinal tract cytology has followed technical advances in this field over the last 60 years. Cytologic samples can be obtained using gastric lavage, abrasive balloons, mucosal brushing, and fine needle aspiration (under percutaneous image guidance, endoscope and endoscopic ultrasound guidance). These advances now allow simultaneous performance of brushing the abnormal mucosa, obtaining fine needle aspirates and excising mucosal biopsy samples for evaluation. Use of endoscopic ultrasound guided fine needle aspirates now help to obtain diagnosis of submucosal lesions, preoperative staging of gastrointestinal tract malignancies and help determine further management of patients. Such advances have brought pathologists to the forefront of the patient management team for the treatment of gastrointestinal tract lesions. This manuscript reviews the advantages and limitations of each cytology associated technique as well as reviews the salient diagnostic features, differential diagnosis and diagnostic pitfalls of gastrointestinal tract lesions. Finally, it suggests the modalities best suited to obtain diagnosis for various gastrointestinal tract lesions.

Epithelioid variant of gastrointestinal stromal tumor: Diagnosis by fine-needle aspiration

Epithelioid gastrointestinal stromal tumors (GISTs) may cause significant diagnostic confusion on fine-needle aspiration (FNA) with carcinomas, neuroendocrine tumors, and melanoma, particularly when metastatic. This study characterizes the cytologic features of nine cases of epithelioid GISTs that were obtained by computerized tomographic guidance in five, by endoscopic ultrasound in three, and from an excised liver tumor in one. Six cases presented as liver masses, one as a perisplenic mass, one as an abdominal mass, and one as a gastric mass. The aspirates revealed mainly single or small clusters of epithelioid cells with a moderate amount of granular to clear cytoplasm, small uniform nuclei with mild to marked nuclear envelope irregularities. Binucleation and intranuclear inclusions were frequent findings. Collagenous stroma was seen in most cases. In three cases, a neuroendocrine tumor was the initial diagnosis. Immunocytochemical staining for c-kit (CD117) was performed on cellblocks in six cases and was positive in five cases. On the subsequent surgical specimen, CD117 was positive in the c-kit-negative cytology case. The diagnosis of GIST should be considered in aspirates of the gastrointestinal tract, liver, mesentery, or abdominal wall mass lesions when epithelioid cells are the predominant cell type. Ancillary studies such as immunohistochemical stains are usually helpful in making a definitive diagnosis.

A novel c-kit positive biphenotypic acute leukemia cell line, TMBL-1, carrying a p53 point mutation

We established and characterized a c-kit positive cell line from the bone marrow of a patient with biphenotypic acute leukemia (BAL). The cell line, designated TMBL-1, carried a His-175 mutant p53. The immunophenotype of the primary leukemia cells at diagnosis was cytoplasmic CD3+, CD7+, CD13+, CD33-, interleukin-7 (IL-7) receptor+ and c-kit -. However, leukemia cells in relapse and TMBL-1 cells were CD33+ and c-kit +. Immunophenotypically, TMBL-1 is a BAL cell line that coexpresses T-lymphoid and myeloid markers which fulfill the criteria of the European Group for the Immunological Characterization of Leukemia. Stem cell factor (SCF), a key regulator of hematopoiesis signaling through c-kit, enhanced the proliferation of TMBL-1 cells. Direct sequencing revealed the conversion at codon 175 of the p53 gene in the TMBL-1 cells. Primary leukemia cells in relapse also carried the same point mutation but not at diagnosis. Moreover, TMBL-1 cells are sensitive to paclitaxel, which could induce p53-independent apoptosis. The biphenotypic features and p53 mutation may be associated with progression to a more malignant type. This cell line may provide new information on the role of SCF in the overlapping area between early T-lymphoid/myeloid cells, and help in the design of new therapies targeted towards p53 mutations.

A comparison of EUS features between CD-117 positive GI stromal tumors and CD-117 negative GI spindle cell tumors

BACKGROUND

GI stromal tumors are spindle cell tumors that stain positive for immunohistochemical CD-117 (c-kit). Prognostic factors for malignancy include size (> or =4 cm), mitotic index (5 mitotic figures/50 high-powered fields), and ulcerated, cystic, or necrotic areas within the tumor. The purpose of this study was to compare these features in c-kit positive vs. c-kit negative tumors.

METHODS

All patients referred for EUS of submucosal lesions were identified, and histopathology, including immunohistochemical staining, was reviewed to determine all diagnoses of GI stromal tumors. Size, echo pattern, and presence of cystic spaces and ulceration were recorded as diagnosed by EUS. Histopathologic diagnoses were made by FNA or endoscopic submucosal-mucosal resection. If surgical resection followed, the surgical diagnosis, staining pattern, mitotic index, and presence of ulceration, necrosis, and nuclear atypia were recorded.

RESULTS

Forty patients (21 men, 19 women; 38 white, 2 African American; mean age 58 +/- 2.6 years) had 46 EUS procedures performed for evaluation of spindle cell tumors. Seventeen stained positive for c-kit (mean age, 59 +/- 3.6 years; range 19 to 80 years) and 12 negative (mean age, 57 +/- 3.8 years; range 31 to 76 years); 11 were not stained for c-kit (excluded from analysis). On EUS, 7 were ulcerated, 3 cystic, and 6 were larger than 4 cm. This group of findings was observed in 12 patients, 11 of whom had c-kit positive tumors (11/17 vs. 1/12; p = 0.006). Tumors positive for c-kit were larger (42.4 +/- 5.5 mm vs. 19.0 +/- 5.9 mm; p = 0.005). There were 13 c-kit positive tumors in the stomach, 2 in the duodenum, and 1 each in the esophagus and at the gastroesophageal junction. Of the 12 c-kit negative tumors, 8 were located in the esophagus and 1 at the gastroesophageal junction (9/12 vs. 2/17; p < 0.01). Surgical resection was performed on 13 patients, 12 of whom had c-kit positive tumors, and 3 of these 12 tumors had greater than 5 mitoses per 50 high-powered field.

CONCLUSIONS

If a GI stromal tumor is suspected, EUS-FNA with immunohistochemical staining should be performed for CD-117 (c-kit). C-kit tumors are more likely to have malignant features and should be resected or subjected to close clinical follow-up.

Fine-needle aspiration cytology and immunocytochemistry in the diagnosis of 24 gastrointestinal stromal tumors: a quick, reliable diagnostic method

The diagnosis of gastrointestinal stromal tumors (GISTs) is generally established on histopathologic examination of surgical specimens. Fine-needle aspiration (FNA), performed under the guidance of ultrasound or computed tomography, is being used with increasing frequency in an attempt to diagnose primary and/or metastatic GISTs before surgery. The present study was undertaken to characterize the cytological appearance of these tumors and to assess the role of cytology, together with immunocytochemistry (ICC), in the diagnosis of GISTs. Twenty-four GISTs diagnosed by FNA cytology at our institution have been reviewed. Immunocytochemical studies with c-kit and CD34 were performed in all cases on current or archival Papanicolaou-stained smears. All cases stained with c-kit, and 19 reacted with CD34. Cytomorphology and immunocytochemical characteristics are discussed. Our results confirm the utility of FNA together with ICC in the diagnosis of primary and/or metastatic GISTs.

Fine-needle aspiration cytology diagnosis of metastatic gastrointestinal stromal tumor in the liver: a report of three cases

Gastrointestinal stromal tumor (GIST) is the designation for a major subset of gastrointestinal mesenchymal tumors that histologically, immunocytochemically, and genetically differ from leiomyomas, leiomyosarcomas, and schwannomas. GISTs derive from the interstitial cells of Cajal and, in addition to variable expression of smooth muscle and neural markers, they characteristically express CD34 and CD117. The cytological appearance, including immunocytochemical and mutational analysis of c-kit gene in primary GIST has been well described. To our knowledge, only two cases of metastatic GIST diagnosed by fine-needle aspiration (FNA) have been reported. We illustrate three cases of metastatic GIST in the liver. Two cases had no prior history of gastrointestinal tumor and the third case had a 4-yr previous history of duodenal tumor. Consistent immunocytochemistry and ultrastructual studies supported the diagnosis of GIST. We emphasize that in the appropriate clinical and radiological setting, a confident diagnosis of GIST can be established by FNA of metastatic lesions.

SU5416 and SU5614 inhibit kinase activity of wild-type and mutant FLT3 receptor tyrosine kinase

Internal tandem duplication (ITD) in the juxtamembrane portion of Fms-like tyrosine kinase 3 (FLT3), a type III receptor tyrosine kinase (RTK), is the most common molecular defect associated with acute myeloid leukemia (AML). The high prevalence of this activating mutation makes it a potential target for molecularly based therapy. Indolinone tyrosine kinase inhibitors have known activity against KIT, another member of the type III RTK family. Given the conserved homology between members of this family, we postulated that the activity of some KIT inhibitors would extend to FLT3. We used various leukemic cell lines (BaF3, MV 4-11, RS 4;11) to test the activity of indolinone compounds against the FLT3 kinase activity of both wild-type (WT) and ITD isoforms. Both SU5416 and SU5614 were capable of inhibiting autophosphorylation of ITD and WT FLT3 (SU5416 concentration that inhibits 50% [IC(50)], 100 nM; and SU5614 IC(50) 10 nM). FLT3-dependent activation of the downstream signaling proteins mitogen-activated protein kinase (MAPK) and signal transducer and activator of transcription 5 (STAT5) was also inhibited by treatment in the same concentration ranges. FLT3 inhibition by SU5416 and SU5614 resulted in reduced proliferation (IC(50), 250 nM and 100 nM, respectively) and induction of apoptosis of FLT3 ITD-positive leukemic cell lines. Treatment of these cells with an alternative growth factor (granulocyte-macrophage colony-stimulating factor [GM-CSF]) restored MAPK signaling and cellular proliferation, demonstrating specificity of the observed inhibitory effects. We conclude that SU5416 and SU5614 are potent inhibitors of FLT3. Our finding that inhibition of FLT3 induces apoptosis of leukemic cells supports the feasibility of targeting FLT3 as a novel treatment strategy for AML.

A case of solitary fibrous tumor of the parotid gland: review of the literatures

We report a rare case of solitary fibrous tumor of the parotid gland. A 47-year-old woman presented with a 3-year-history of left-sided subauricular swelling. Computed tomographic scans and magnetic resonance images revealed a well-defined and dumbbell-shaped mass, measuring about 30 mm in its greatest dimension, in the left parotid gland. Because the tumor occupied both superficial and deep lobes of the gland, she underwent total parotidectomy with preservation of the facial nerve. The microscopic finding showed short-spindle and ovoid cells arranged in a haphazard pattern with interspersed thin collagen fibrils. Immunohistochemically, the tumor cells were strongly positive for CD34, bcl-2 and vimentin, whereas stains for S-100, cytokeratin, smooth muscle actin, collagen type IV and CD117 (KIT) were negative. On the basis of these findings, the tumor was diagnosed as solitary fibrous tumor. Her post-operative course was uneventful, and she is currently free from disease 14 months after surgery. Diagnosis, clinical behavior and treatment of solitary fibrous tumor are reviewed from perusal of the literature.

Initial experience with EUS-guided trucut needle biopsies of perigastric organs

BACKGROUND

The aims of this study were to determine the feasibility, safety, and yield of a 19-gauge EUS-guided-trucut needle for obtaining biopsy specimens of perigastric organs.

METHODS

The study was performed in swine under general anesthesia. EUS-guided trucut needle biopsy specimens were obtained from the spleen, liver, pancreas body, and left kidney. Biopsy specimens were assessed for size, fragmentation, and representation of the target organ.

OBSERVATIONS

Twenty-eight biopsy specimens were obtained from the 4 target organs with two needles. Median biopsy length was 6 mm (spleen), 4 mm (liver), 6 mm (left kidney), and 2 mm (pancreas body). Of all the specimens, 75% to 100% had tissue representative of the target organ. EUS visualization of the needle was excellent and no complications were identified.

CONCLUSIONS

Use of the trucut needle under EUS guidance to obtain biopsy specimens of perigastric organs appears safe and yields specimens that are representative of the target organ sampled. Further study of the utility and safety of this needle in humans is warranted.

The co-expression of CD117 (c-kit) and osteocalcin in activated bone marrow stem cells in different diseases

It is still difficult to identify a potential stem cell in the bone marrow which can give rise to haematopoiesis and mesenchymal cells. In the past, the stem cells for both tissues were considered to be from different stem cell pools, but it has been shown recently in vitro and in vivo that there is an unexpected plasticity at least among early haemopoietic progenitors which can give rise also to mesenchymal tissue. In an attempt to identify stem cells in the bone marrow, which are common precursors to both lineages, we observed that fibroblast-like periosteal cells changed their morphology towards an osteoblastic differentiation with a more cuboidal or triangular morphology especially close to metastatic infiltrates. As a marker for haemopoietic progenitors, we used an antibody against the tyrosine kinase receptor c-kit (CD117) and an anti-osteocalcin antibody to stain mesenchymal cells with a osteoblastic potential. Normal bone marrow specimens only showed a discrete expression pattern of CD117 and osteocalcin, but periosteal stem cells, which strongly co-express the applied haemopoietic and mesenchymal markers, were found particularly in the bone marrow of patients with infiltrates of malignant lymphoma or metastasis from prostate or breast cancer. The evaluation of bone marrow specimens from patients with an aplastic syndrome or myelodysplastic syndrome showed a more heterogenous expression pattern. Our results show that a stem cell candidate common to haematopoiesis and mesenchymal progeny can be detected in bone marrow specimens after activation, as demonstrated by the co-expression of CD117 and osteocalcin, which also seems to be associated with haematological diseases or metastatic infiltration in the bone marrow.

KIT mutations are common in incidental gastrointestinal stromal tumors one centimeter or less in size

Gastrointestinal stromal tumors (GISTs) are mesenchymal neoplasms of the gut wall that express the receptor tyrosine kinase KIT. Somatic mutations that result in constitutive activation of KIT kinase have been identified in a number of studies of GISTs, although the reported frequency of these mutations has varied over a wide range (20 to 92%). Several reports have suggested that KIT gene mutations are more common in malignant GISTs than in benign lesions, and it has been proposed that mutations in exon 11 of KIT are a negative prognostic factor. To maximize sensitivity for KIT mutations we have adapted denaturing high-pressure liquid chromatography as a method for screening polymerase chain reaction amplimers of exons 9, 11, 13, and 17 from GIST genomic DNA. This approach was used to assess the frequency of KIT mutations in 13 morphologically benign, incidentally discovered, GISTs identified at autopsy, endoscopy, or laparotomy for unrelated disease. Representing the smallest pathologically recognizable GISTs, these lesions ranged in size from 4 to 10 mm in diameter and were all immunohistochemically positive for KIT. Eleven of the 13 tumors had sequence-confirmed mutations in KIT, including 10 mutations in exon 11 (77%) and one mutation in exon 9 (7.7%). The remaining two tumors were wild type for exons 9, 11, and 17; one of these was also analyzed for exon 13 and was wild type in this exon as well. The mutations found in the incidental GISTs were identical to those that have been documented in larger GISTs. In addition, the overall frequency of mutations in the incidental tumors (85%) did not differ significantly from that we previously reported in a series of 72 advanced/metastatic GISTs (86%), strongly supporting the view that activating mutations in KIT are acquired very early in the development of most GISTs. The findings suggest that KIT mutations per se are of little prognostic importance in GISTs.