MIC2 Expression Research Articles

Primitive neuroectodermal tumor of the kidney: an experience of three cases

BackgroundPrimitive neuroectodermal tumors (PNET) are highly aggressive tumors belonging to the Ewing’s sarcoma family. Primitive neuroectodermal tumor is a group of bone and soft tissue tumor arising from neuroectodermal tissues. They are characterized by the expression of MIC2 and neural markers like neuron-specific enolase, synaptophysin, S-100, vimentin, Leu-7, and the presence of the EWS-FLI1 translocation. It is a rare malignancy with only about 150 cases being published worldwide. The tumor usually presents with non-specific symptoms such as abdomen pain and hematuria. Inferior vena cava (IVC) involvement by renal PNET is extremely rare with only a handful cases reported in the literature and is a clinically challenging scenario. There is a dearth of data on the management of this disease; further, the management of this disease in current scenarios is not well reported. We report our experience with three cases over 11 years which spans all three spectrums of the disease: localized, locally advance and metastasis. Case presentationCase 1: 37-year-old gentleman presenting with hematuria found to have right renal tumor with IVC invasion which was found to be unresectable intraoperatively. Patient was started on chemotherapy but deteriorated and died 3 months later. Case 2: 38-year-old gentleman presenting with abdominal pain found to have locally advanced left renal tumor. Patient developed local recurrence and metastasis 15 months after resection but had stable disease for nearly 4 years before developing acute myeloid leukemia and withdrawing consent for treatment. Case 3: 13-year-old girl who presented with right abdominal mass and subsequently found to have localized disease. After aggressive chemotherapy, patient is now recurrence-free after nearly 11 years.ConclusionsOur study aims to show the spectrum of renal primitive neuroectodermal tumors with outcomes in all three clinical scenarios, with the aim of reinforcing that high index of suspicion for this disease is required in young patients presenting with aggressive disease, and immunohistochemistry should be used when in doubt, as outcomes are greatly improved with adjuvant chemotherapy.

S2027 Ewing's Sarcoma: A Difficult Diagnosis to Swallow

INTRODUCTION: Ewing sarcoma family of tumors (EFT) compromises of a spectrum of similar histological undifferentiated cells. EFT includes Ewings Sarcoma (ES) and Primitive Neuroectodermal Tumor (PNET). These tumors are rare and aggressive with a tendency of early metastatic spread. Peak incidence are between ages of 10-15 years of age; however, 30% can occur in adults over the age of 20. EFT affect mainly Caucasians and are extremely uncommon in other races. Most common origin occurs from the bone of the extremities and axial skeleton. These tumors are not commonly found in the gastrointestinal tract. Our case demonstrates a rare presentation of metastatic Ewing Sarcoma found during evaluation for dysphagia. CASE DESCRIPTION/METHODS: 69 year old female who is a daily smoker with history of large cell lymphoma (previously treated with Adriamycin) and Barrett's esophagus presented with dysphagia. Labs were relevant for iron deficiency anemia. EGD revealed a fungating mass in an area of Barretts esophagus. The mass was not bleeding, non obstructing and partially circumferential. Biopsies from the mass revealed Ewing sarcoma (ES) based on histological stains. Microscopically the cells were arranged in cords suggestive of a neuroectodermal tumor. Fluorescent in situ hybridization (FISH) testing was negative for EWSR fusion protein. Cells were strongly positive for CD-99 and weakly positive for FLI1 also highly suggestive of ES. Further imaging revealed metastatic disease to the liver. Liver lesions were also biopsied confirming diagnosis of extra-skeletal Ewings Sarcoma. DISCUSSION: Soft tissue Ewing Sarcoma patients are older and more likely to be female. These tumors do express high levels of cell surface glycoproteins such as CD99, MIC2, and p30. MIC2 expression is a sensitive diagnostic marker for ES however it lacks specificity. Typically ES can be diagnosed with immunohistochemical stains for CD99 in the right clinical setting. However, if the presentation is atypical, such as in our case, further confirmatory testing with Next Generation Sequencing to detect translocation or point mutations are needed. Because of the vast differentials molecular genetics plays a large role in diagnosis. Translocations in EWSR1 gene on chromosome 22q12 are found in 85% of cases and can be detected using FISH analysis. This case illustrates the importance of timely establishment of type of esophageal cancer in order to obtain prompt molecular genetic assessments in order to confirm histological diagnosis.Figure 1.: Lower esophageal fungating, non obstructing, partially circumferential mass found on EGD.Figure 2.: The cells are small to medium sized, and are arranged in cords, interspersed with smooth muscle fibers suggestive of a neuroectodermal tumor.Figure 3.: Immunohistochemical stain positive for CD99 (cell surface glycoprotein) found in Ewings Sarcoma.

A Rare, yet Aggressive, Intra-Abdominal Malignancy: Ewing Sarcoma of the Pancreas

Introduction: Ewing sarcoma (ES) is a malignant bone tumor of long-bones, which typically occurs in children. Extraskeletal Ewing sarcoma (EES) is a poorly differentiated soft tissue sarcoma within morphologic category of ‘small-round-cell’ tumors and accounts for less than 1% of soft tissue sarcomas. Only 24 cases have been reported in the literature. Herein, we present an interesting case of EES of pancreas. Case Description: 34-year-old male presented to clinic secondary to insidious onset, generalized abdominal pain for past 1-month. Physical exam revealed non-tender, moderately distended abdomen with a palpable mass above the umbilicus. Initial lab workup showed mild elevation of AST 91 (0-50 U/L) and alkaline-phosphatase 337 (38-126 U/L). CT abdomen showed lobulated heterogeneous mass with necrotic transformation in body and tail of pancreas, with multiple liver lesions. Resultantly, a working diagnosis of adenocarcinoma of pancreas with metastasis to liver was made. A CT-guided biopsy of pancreatic and hepatic mass showed small, blue, round cells with scant cytoplasm. Hence, the previous diagnosis of pancreatic adenocarcinoma was disregarded, and other differential diagnoses including EES, neuroblastoma, non-Hodgkin's lymphoma vs desmoplastic small blue round cell tumor were considered. Further testing with immunohistochemistry confirmed the diagnosis of EES. Subsequently, patient was started on chemotherapy with doxorubicin, cyclophosphamide and vincristine. After one round of chemotherapy, patient developed neutropenic fever and died after 1-month from a complicated hospital course. Discussion: This case highlights an extremely rare type of soft tissue sarcoma (EES) at an unusual location. The diagnosis of ESS is confirmed by immunohistochemistry as imaging modalities often remain nonspecific. Histologically, ES and EES are described as small, blue, round cells with hyperchromatic nuclei and scant cytoplasm, with molecular expression of MIC2, CD99 and antibody against FLI1 centered in nucleus. Though 85% of the ES cases are associated with chromosomal translocation t(11;22) and q(24;12), it remains non-specific. EES is an aggressive and malignant tumor with a 5-year survival rate of around 50%. Surgical excision, plus chemotherapy and radiotherapy is the main modality of treatment. Though EES is rare, physicians should be acquainted with and consider it in the differential diagnosis, as early recognition and intervention is very critical.1397_A.tif Figure 1: Necrotic mass (14.8cm x 5.6cm x 6.7cm) again visualized in the pancreas along with multiple hypo-attenuated liver lesions.1397_B.tif Figure 2: Small, blue, round cells with high NC ratio, dark chromatin pattern with scant cytoplasm. Tumor cells positive for vimentin; negative for CD45, CD117, chromogranin, synaptophysin, pan cytokeratin, smooth muscle actin, desmin, HMB-45, S-100 and CD138. Pattern is highly consistent with high grade soft tissue sarcoma- EES.

Unusual Presentation of Ewing Sarcoma in the Adrenal Gland: A Secondary Malignancy from a Survivor of Burkitt Lymphoma

The occurrence of Ewing sarcoma as a secondary malignancy is an extremely rare event in long-term cancer survivors. In addition, the occurrence of Ewing sarcoma in the adrenal gland is highly unusual. In this case report, we treated a 20-year-old male patient with cyclophosphamide, doxorubicin, vincristine, dexamethasone, and methotrexate and cytarabine chemotherapy following a diagnosis of Stage IV Burkitt lymphoma. Following complete remission, he had been maintained for 2 years without evidence of disease. However, a regular follow-up computed tomography scan found a left adrenal gland mass and a biopsy revealed positive membrane-localized mic-2 expression (CD99) and the presence of the translocation of the EWSR1 gene. To our knowledge, this is the first case report of Ewing sarcoma occurring in the adrenal gland of a patient who was treated with cyclophosphamide, doxorubicin, vincristine, dexamethasone/methotrexate and cytarabine chemotherapy for Burkitt lymphoma.

Primitive neuroectodermal tumor of the kidney

We report a 21-year-old man with a primitive neuroectodermal tumor (PNET) of the kidney that was difficult to distinguish from other small round cell tumors, e.g., small cell carcinoma, malignant lymphoma, and Wilms' tumor. Pathologically, a primitive rosette-like pattern was shown by H&E staining; expression of MIC-2 was indicated by an immunohistochemical test; rather primitive organelles were observed by an ultrastructural method; and translocation of chromosome 22 was confirmed by FISH. We therefore diagnosed the current case as PNET. The patient had undergone a right radical nephrectomy more than 1.5 years earlier. After neither metastases nor recurrences for 0.5 year, imaging examinations revealed masses in his liver. He received chemotherapy and underwent surgery again, but the masses were not composed of viable tumor cells. PNET of the kidney is extremely rare; fewer than 30 cases have been reported in the English literature, and there are few data on the expression of p53, ki67, and bcl2. We investigated the relationships between these markers in the current case using immunohistochemical tests and observed strong expression of p53, Ki-67, and bcl-2. Such results generally indicate poor prognosis, and the patient eventually had some masses in his liver, but no viable tumor cells were found. The prognostic significance of these various markers in PNET of the kidney still remains unclear, but p53, ki-67, and bcl-2 might not be so important as indicators of prognosis in the kidneys as they are in other organs. Further studies are needed to investigate this, and we hope that the patient recovers completely.

Primitive neuroectodermal tumor: Rare, highly aggressive differential diagnosis in urologic malignancies

Objectives Peripheral primitive neuroectodermal tumor (PNET) is a highly aggressive neoplasm belonging to the Ewing family of tumors. It is characterized by the expression of MIC2 and neural markers (eg, neuron-specific enolase, synaptophysin, S-100, vimentin, Leu-7), and the presence of the EWS-FLI1 translocation. Methods We performed a MEDLINE search for PNET in urologic malignancies. Additionally, we report on 2 cases of renal and 1 case of bladder PNET. The data obtained by reviewing patients with renal PNET were analyzed using Kaplan-Meier analysis. Results Renal PNET is diagnosed in young adults (median age 24 years). In contrast, the incidence of bladder PNET seems to be dependent on a defective immune mechanism. Patients often present with pain (84%), palpable tumor (60%), and hematuria (38%). The radiologic findings are uncharacteristic; therefore, the diagnosis should be based on the histologic and immunohistochemistry findings. Renal and bladder PNET are both often diagnosed at an advanced stage and, therefore, the prognosis is poor, despite aggressive multimodal treatment (surgery, polychemotherapy, radiotherapy). We identified palpable tumor masses (log-rank test, P = 0.0027) and synaptophysin expression (log-rank test, P = 0.0422) as prognostic unfavorable markers for renal PNET. Conclusions Renal PNET should be considered in young patients who present with the classic triad of renal cancer, hematuria, and pain and palpable tumor. Once PNET is diagnosed, multimodal treatment (radical surgery, multidrug chemotherapy, radiotherapy) must be initiated. Despite this, the prognosis is poor if distant metastases are present. Furthermore, palpable tumor masses and synaptophysin expression are associated with a shorter cancer-specific survival.

Toxoplasma MIC2 Is a Major Determinant of Invasion and Virulence

Like its apicomplexan kin, the obligate intracellular protozoan Toxoplasma gondii actively invades mammalian cells and uses a unique form of gliding motility. The recent identification of several transmembrane adhesive complexes, potentially capable of gripping external receptors and the sub-membrane actinomyosin motor, suggests that the parasite has multiple options for host-cell recognition and invasion. To test whether the transmembrane adhesin MIC2, together with its partner protein M2AP, participates in a major invasion pathway, we utilized a conditional expression system to introduce an anhydrotetracycline-responsive mic2 construct, allowing us to then knockout the endogenous mic2 gene. Conditional suppression of MIC2 provided the first opportunity to directly determine the role of this protein in infection. Reduced MIC2 expression resulted in mistrafficking of M2AP, markedly defective host-cell attachment and invasion, the loss of helical gliding motility, and the inability to support lethal infection in a murine model of acute toxoplasmosis. Survival of mice infected with MIC2-deficient parasites correlated with lower parasite burden in infected tissues, an attenuated inflammatory immune response, and induction of long-term protective immunity. Our findings demonstrate that the MIC2 protein complex is a major virulence determinant for Toxoplasma infection and that MIC2-deficient parasites constitute an effective live-attenuated vaccine for experimental toxoplasmosis.

Primitiver neuroektodermaler Tumor der Niere

Primitive neuroectodermal Tumor (PNET) is a rare malignant tumor of young adult. Patients often present with the classical trias of renal cancer (pain, haematuria, palpable tumor). Specific radiological signs are missing, and therefore a PNET is often diagnosed postoperatively. It is characterized by the expression of MIC2, neural markers (Vimentin, S-100, Synaptophysin) and EWS/FLI1-translocation. The tumor is often diagnosed in advanced stage, and prognosis is poor despite of multimodal treatment including radical nephrectomy, polychemotherapy (vincristine, adriamycin, cyclophosphamid, etoposide, ifosfamide) and radiation in case of metastases or incomplete resection of primary tumor. We represent two cases of metastatic renal PNET in a 28- and 39-year-old patient. Due to the multimodal treatment a partial and a complete remission was achieved, respectively.

Immunoreactivity of MIC2 (CD99) and Terminal Deoxynucleotidyl Transferase in Bone Marrow Clot and Core Specimens of Acute Myeloid Leukemias and Myelodysplastic Syndromes

MIC2 ("thymus leukemia") antigen has been shown to be expressed by T cells and monocytes, as well as B cells and granulocyte-lineage cells. It is most intensely expressed by the most immature thymus T-lineage cells and is more intensely expressed by CD34-positive/CD33-positive myeloid cells (compared to more mature myeloid cells) and the earliest CD34-positive/CD10-positive B-cell precursor cells (compared to cells of later B-cell precursor stages). CD99 (MIC2) is characteristically expressed in precursor B- and T-cell lymphoblastic lymphomas/leukemias, as well as in Ewing sarcoma/primitive neuroectodermal tumors (ES/PNET). It has also been shown to be expressed in a few terminal deoxynucleotidyl transferase (TdT)-positive myeloid processes, but has been uniformly negative in TdT-negative myeloid processes. A more recent study showed that 43% of acute myeloid leukemias (AMLs) and 55% of chloromas express CD99, concluding that CD99 is commonly expressed in AML and rarely seen in myeloproliferative disorders, myelodysplastic syndromes, or normal bone marrow. Although this study speculated that MIC2 expression was probably not limited to TdT-positive AML, there was no comparison with TdT reactivity in this study. Since AML and high-grade myelodysplastic syndrome may occasionally be difficult to distinguish morphologically from acute lymphoblastic leukemia and ES/ PNET, we undertook a study to analyze MIC2 expression in conjunction with TdT reactivity in distinguishing AML or high-grade myelodysplastic syndrome from acute lymphoblastic leukemia and ES/PNET. We studied bone marrow core and clot paraffin specimens from AML (classified according to criteria of the World Health Organization; n = 49), myelodysplastic syndromes (n = 4), precursor B-cell acute lymphoblastic leukemia (n = 4), ES/PNET (n = 1), and normal bone marrow (n = 3) with MIC2 (CD99) and TdT immunohistochemistry. Overall, CD99 was expressed in 24 (49%) of 49 AML cases, including all (11/11) TdT-positive cases. CD99 was expressed in all subtypes of AML except M5. Myelodysplastic syndromes and normal bone marrow specimens were uniformly CD99 negative. Expression of TdT was limited to a subset of AML-M0, -M1, -M2, and -M4, and AML with multilineage dysplasia. In contrast to a previous study, CD99 expression was not restricted to TdT-positive hematologic proliferations. In particular, the CD99-positive M3 and M7 AMLs were TdT negative. An M5 AML may likely be excluded based on a uniform TdT-negative/CD99-negative immunophenotype. In addition, in our experience, CD99 should be routinely evaluated on bone marrow clots, owing to decreased reactivity or loss of reactivity in rapid decalcifying (RDO) solution-decalcified specimens.

Preparing for an invasion: charting the pathway of adhesion proteins to Toxoplasma micronemes

Toxoplasma gondii is an apicomplexan parasite capable of infecting a broad host range including humans. The tachyzoite lytic cycle begins with active invasion of host cells involving the release of adhesive proteins from apical secretory organelles called micronemes. A protein complex consisting of the transmembrane adhesin MIC2 and a tightly associated partner, M2AP, is abundantly released from the micronemes. Similar to many proteins in a regulated secretory pathway, T. gondii proteins destined for micronemes and rhoptries (another secretory organelle associated with invasion) undergo proteolytic maturation. M2AP contains a propeptide that is removed in a post-Golgi compartment. By expressing an M2AP propeptide deletion mutant in the M2AP knockout background, we show that the propeptide is required for the MIC2-M2AP complex to exit from the early endosome. Although a cleavage-resistant M2AP mutant was able to efficiently reach the micronemes, it was unable to rapidly mobilize from the micronemes to the parasite surface. Strikingly, both mutants were unable to support normal parasite invasion and were partially attenuated in virulence to a degree that is indistinguishable from M2AP knockout parasites. Conditional expression of MIC2 showed that it is also required for correct M2AP sorting to the micronemes. These parasites were severely impaired in invasion efficiency. They switched almost exclusively to a non-productive circular gliding motility and were incapable of establishing an infection in mice when inoculated at a normally lethal dose. These findings underscore the importance of correct trafficking of invasion-related proteins. Our results also serve as a basis for future studies aimed at defining the branch points of protein sorting in T. gondii and at a deeper understanding of the precise roles of M2AP propeptide and MIC2 targeting motifs in MIC protein trafficking.

Rapid invasion of host cells by Toxoplasma requires secretion of the MIC2-M2AP adhesive protein complex.

Vertebrate cells are highly susceptible to infection by obligate intracellular parasites such as Toxoplasma gondii, yet the mechanism by which these microbes breach the confines of their target cell is poorly understood. While it is thought that Toxoplasma actively invades by secreting adhesive proteins from internal organelles called micronemes, no genetic evidence is available to support this contention. Here, we report successful disruption of M2AP, a microneme protein tightly associated with an adhesive protein called MIC2. M2AP knockout parasites were >80% impaired in host cell entry. This invasion defect was likely due to defective expression of MIC2, which partially accumulated in the parasite endoplasmic reticulum and Golgi. M2AP knockout parasites were also unable to rapidly secrete MIC2, an event that normally accompanies parasite attachment to a target cell. These findings indicate a critical role for the MIC2-M2AP protein complex in parasite invasion.

Microarray analysis of gene-expression profiles in diffuse large B-cell lymphoma: identification of genes related to disease progression.

To identify genes that are associated with progression of malignant lymphoma, the expression profiles of 18 432 genes were analyzed in diffuse large B‐cell lymphomas at early (stages I and II, 6 cases) and advanced stages (stages III and IV, 9 cases) by means of cDNA microarrays. By comparing expression profiles between localized and advanced lymphomas, a number of genes that were differentially expressed were identified: 48 genes with increased expression and 30 genes with reduced expression in advanced‐stage diffuse large B‐cell lymphomas. Increased expression of MPHOSPH1, RUVBL1, CHN2, PSA and CDC10 genes, and reduced expression of COL1A2, COL4A1, FBLN5, CLECSF6, MIC2, CAV1 and S100A10 genes in the advanced lymphoma group were confirmed by semi‐quantitative reverse transcription‐PCR. RUVBL1 and PSA expression was further confirmed by real‐tune quantitative PCR, whose results paralleled the microarray data. The highly expressed genes encode proteins that promote cell proliferation and the genes with reduced expression encode adhesion proteins and target protein for cytotoxic T‐lymphocytes. These findings suggested that analysis with cDNA microarrays is a useful approach for identifying genes related to tumor progression and their products could be potential tumor markers or disease‐specific targets for anti‐tumor therapy.

Alternative EWS‐FLI1 fusion gene and MIC2 expression in peripheral and central primitive neuroectodermal tumors

Primitive neuroectodermal tumors (PNET) occur either in the central nervous system (CNS; central PNET, cPNET) or in the peripheral sites (peripheral PNET, pPNET). Recent molecular approaches have been defining a new concept of PNET, that is, the pPNET including Ewing's sarcoma (ES) which expresses MIC2 glycoprotein and shows the specific chimeric gene of EWS‐FLI1. The expression of MIC2 and the genetic rearrangement of EWS‐FLI1 are considered to be highly specific to the pPNET/ES. This study examined the expression of MIC2 and EWS‐FLI1 gene by means of immunohistochemistry and reverse transcriptase–polymerase chain reaction (RT‐PCR) on various small round cell tumors originating in the CNS or non‐CNS organs. All peripheral PNET tested expressed MIC2 and were positive for EWS‐FLI1 (11/11). In contrast, all cPNET and other blastic CNS tumors were negative for MIC2: medulloblastoma (0/3), cerebral PNET (0/2), spinal PNET (0/2), glioblastoma (0/2), retinoblastoma (0/3), and pineoblastoma (0/2). These MIC2‐negative tumors were also negative for the chimeric gene product of EWS‐FLI1. Interestingly, one PNET originating in the intracranial dura mater was positive for both MIC2 and EWS‐FLI1 fusion gene. The results indicate that cPNET lacks any genetic or protein markers, except for a meningeal PNET which falls into the same phenotypic spectrum of pPNET.

Alternative EWS-FLI1 fusion gene and MIC2 expression in peripheral and central primitive neuroectodermal tumors.

Primitive neuroectodermal tumors (PNET) occur either in the central nervous system (CNS; central PNET, cPNET) or in the peripheral sites (peripheral PNET, pPNET). Recent molecular approaches have been defining a new concept of PNET, that is, the pPNET including Ewing's sarcoma (ES) which expresses MIC2 glycoprotein and shows the specific chimeric gene of EWS-FLI1. The expression of MIC2 and the genetic rearrangement of EWS-FLI1 are considered to be highly specific to the pPNET/ES. This study examined the expression of MIC2 and EWS-FLI1 gene by means of immunohistochemistry and reverse transcriptase-polymerase chain reaction (RT-PCR) on various small round cell tumors originating in the CNS or non-CNS organs. All peripheral PNET tested expressed MIC2 and were positive for EWS-FLI1 (11/11). In contrast, all cPNET and other blastic CNS tumors were negative for MIC2: medulloblastoma (0/3), cerebral PNET (0/2), spinal PNET (0/2), glioblastoma (0/2), retinoblastoma (0/3), and pineoblastoma (0/2). These MIC2-negative tumors were also negative for the chimeric gene product of EWS-FLI1. Interestingly, one PNET originating in the intracranial dura mater was positive for both MIC2 and EWS-FLI1 fusion gene. The results indicate that cPNET lacks any genetic or protein markers, except for a meningeal PNET which falls into the same phenotypic spectrum of pPNET.

Immunoreactivity of MIC2 (CD99) in Acute Myelogenous Leukemia and Related Diseases

MIC2 is characteristically expressed in lymphoblastic lesions and Ewing's/primitive neuroectodermal tumor sarcomas. Although MIC2 has recently been reported in chloroma and rare terminal deoxynucleotidyl transferase–positive acute myelogenous leukemia (AML), the incidence and the significance of MIC2 (CD99) immunoreactivity in myeloid lesions is not clear. In this study, we evaluated MIC2 positivity in a variety of myeloid diseases and normal marrow to determine its incidence and distribution in myeloid diseases; its correlation with flow cytometric and cytogenetic data in AML; and its association with leukemic transformation, relapse, and chloroma formation. Paraffin sections of 11 chloromas and 94 bone marrow core biopsies from 66 patients were stained with CD99 monoclonal antibody 12E7. Of 94 bone marrow core biopsies, there were 30 AML (fragment antigen binding M0 to M6), 23 remissions, 5 relapses, 12 myeloproliferative disorders, 13 myelodysplastic syndromes, and 11 normal marrows from patients who did not have leukemia. CD99 immunoreactivity was evaluated with light microscopy. MIC2 expression was seen in leukemic blasts in 6 of 11 chloromas (55%) and 13 of 30 AML (43%) but rarely in myeloproliferative disorders, myelodysplastic syndromes, remission, and normal marrow. CD99 tended to be positive in M1-, M3-, and HLA-Dr–negative AML and negative in AML with relapse. MIC2 expression did not correlate with the karyotype independent of French-American-British Cooperative Group classification and the disease remission or occurrence of chloroma in AML. We concluded that MIC2 is commonly expressed in leukemic blasts of AML and is not predictive of leukemic transformation from myeloproliferative disorders and myelodysplastic syndromes or chloroma formation. Caution should be taken when using MIC2 as a marker for Ewing's sarcoma/primitive neuroectodermal tumor or lymphoblastic lymphoma on paraffin sections of either soft tissue or bone marrow specimens.

Ewing's Sarcoma and Peripheral Primitive Neuroectodermal Tumor of Bone and Soft Tissue

The histological diagnosis of Ewing's sarcoma (Es) continues to be a difficult task for pathologists. A number of new Es varieties has been described, leading to further complexity. Conventional Es, atypical Es, and peripheral neuroectodermal tumor (pPNET), including peripheral neuroepithelioma, belong genetically to the same family of neoplasms, displaying common chromosomal rearrangements and analogous gene reorganizations. The main translocations are t(11;22) and t(21;22), with genes EWS, FLI-1 and ERG being involved, as well as other members of the ETS family of transcription factors. The prevalence of morphology should be maintained with the use of conventional histological techniques and supported with the analysis of the expression of CD99 Mic2 (HBA 71, 0.13) antigen, which is present in over 90% of cases, as well as with FLI-1 rearranged gene derived protein. Moreover, FISH and RT-PCR in paraffin-embedded tumor tissue may be of use in extremely difficult cases for differential diagnosis. Nevertheless, a number of mixed tumor types, such as primitive sarcoma or biphenotypic sarcoma, may show structural and genetic diversity, thus rendering their diagnosis even more complex.

Esthesioneuroblastoma is not a member of the primitive peripheral neuroectodermal tumour-Ewing's group.

Esthesioneuroblastoma (ENB) is a rare, site-specific, locally aggressive neuronal malignancy so far thought to belong to primitive peripheral neuroectodermal tumour-Ewing's tumour (pPNETs-ETs). Its anatomical location, in addition to morphologic, immunophenotypic and ultrastructural features, suggests its origin in the neuronal or neuroendocrine cells of the olfactory epithelium. However, the cytogenetic and molecular data currently available appear controversial on the presence of the typical translocation t(11;22)(q24;q12) and of trisomy 8, chromosomal changes that characterize the tumours belonging to the pPNETs-ETs. Herein we have analysed five ENB tumour specimens for trisomy 8 by fluorescence in situ hybridization (FISH), for the presence of EWS gene rearrangements by FISH, reverse transcription polymerase chain reaction and Southern blot analyses, as well as for the expression of the Ewing sarcoma-associated MIC2 antigen by immunohistochemistry. Neither EWS/FLI-I, EWS/ERG and EWS/FEV fusion genes nor MIC2 expression were found in any tumour, whereas trisomy 8 was found in one case only. Moreover, DNA from three cases analysed by Southern blot did not show EWS gene rearrangements. Our results support the evidence that ENB is not a member of the pPNETs-ETs. © 1999 Cancer Research Campaign

Androgen regulation of the human pseudoautosomal geneMIC2, a potential marker for prostate cancer

Using the differential display-polymerase chain reaction technique to identify androgen-responsive genes in the human prostatic tumor cell line LNCaP, we cloned an expression tag homologous to the human pseudoautosomal gene MIC2. The role of MIC2 in the prostate had not previously been studied. We used a series of cell lines derived from LNCaP that varied in their degree of differentiation and metastatic potential to assess the relationship between MIC2 expression and androgen responsiveness in prostate cancer. The expression of MIC2 mRNA and its product E2 was upregulated by androgen in a dose- and time-dependent manner in the parental LNCaP line and correlated with the expression of prostate-specific antigen. In the LNCaP sublines and an androgen-repressed invasive human prostate cancer cell line (ARCaP), MIC2 gene expression was not regulated by androgen and was associated with poorer differentiation, decreased androgen sensitivity, and higher metastatic potential. Immunohistochemical analyses indicated that E2 was expressed in tissues from patients with primary prostate cancer (16 of 20), in fetal prostatic tissues (low levels in all 10 fetal tissues assessed), and sporadically in benign prostatic hyperplasia tissues (one of four). The normal prostate tissues did not show positive E2 staining, with the exception of one central-zone section from one of the eight normal prostate samples assessed. These findings suggest that deregulation of expression of the human pseudoautosomal gene MIC2 occurred in the prostate.

MIC2, TdT, bcl-2, and CD34 expression in paraffin-embedded high-grade lymphoma/acute lymphoblastic leukemia distinguishes between distinct clinicopathologic entities

We propose that 12E7 (CD99) expression, along with TdT, bcl2, and CD34 reactivity in lymphoblastic lymphoma (LyL)/acute lymphoblastic leukemia (ALL), distinguishes this group of neoplasms from small noncleaved cell lymphomas (SNCLs) in both pediatric and adult patients, thereby narrowing the differential diagnosis of high-grade non-Hodgkin's lymphomas and acute lymphoblastic leukemias in paraffin sections. 12E7 (CD99) is one of a group of available antibodies that recognizes the product of the mic-2 gene, which was originally identified in ALL. Despite this, most clinicopathological research has focused on the reactivity of 12E7 in a subset of the small round cell tumors of childhood. Although TdT is widely used in the subtyping of blastic leukemias, its use in the distinction of high-grade lymphomas in paraffin sections has been limited. We collected 24 cases of LyL/ALL (13 B-cell and 11 T-cell) and 15 cases of SNCL from 1984 through 1993. We confirmed the diagnoses using morphology and analysis of immunologic data. We performed immunohistochemistry with the 12E7 antibody, TdT, bcl-2, and CD34 on formalin-fixed, paraffin-embedded material. The patients' ages ranged from 4 to 81 years; nine of the study patients were children. Sixteen of the 24 LyL/ALLs stained with 12E7. In contrast, none of the 15 cases of SNCL reacted with this antibody (chi-square P < .0001). A larger percentage of T-cell LyL/ALLs reacted with 12E7 than did B-cell LyL/ALLs (82% v 54%). Sixteen of 20 LyL/ALLs reacted with the anti-TdT antibody, as compared with none of 11 SNCLs (chi-square P < .0001). Six LyL/ALLs were CD34 positive (of 23), and none of the SNCLs were CD34 positive (0 of 12) (chi-square P = .0519). Bcl-2-positive cases were found among both LyL/ ALLs and SNCLs, although they were more prevalent among LyL/ ALLs (92% v 25%; chi-square P < .0001). When one considers the differential diagnosis of a high-grade lymphoma/acute lymphoblastic leukemia, positive reactions with 12E7, TdT, bcl-2, and CD34 support the diagnosis of LyL/ALL over SNCL. Moreover, we present data that suggests that evaluating for TdT in formalin-fixed paraffin-embedded tissue is a more sensitive test than using either 12E7, bcl-2 or CD34 alone.

Primary cutaneous neuroendocrine tumors: Diagnostic use of cytogenetic and MIC2 analysis

Merkel cell carcinoma (MCC) is a primary cutaneous neoplasm most commonly involving older adults. The cell of origin is thought to be the Merkel cell, a cutaneous neurosecretory cell. However, other neuroectodermal tumors may present in the skin and may be difficult to distinguish from MCC, including peripheral neuroectodermal tumors (PNET) and metastatic small cell carcinoma. We examined a primary cutaneous tumor of an 18-year-old which was strongly positive for cytokeratin (CK), neuron-specific enolase (NSE), and 12E7, an antibody to the protein determined by the MIC2 gene. Electron microscopy showed paranuclear aggregates of filaments and no cytoplasmic processes. These findings were considered to be consistent with MCC. Cytogenetic analysis demonstrated 46,XX,der(1)t(1;3;22)(lqter→pa34::3q28→q11::22q12→qter),der(3)t(1; 3) (pter→q11::1p35-pter),der(22)t(3; 22) (22pter→q11::?3q29→qter). This was confirmed by chromosome painting using probes for chromosomes 1, 3, and 22. Peripheral neuroectodermal tumors (PNETs) show a characteristic translocation involving the same breakpoint on chromosome 22 that was present in this tumor. PNETs can also be CK and NSE positive. The MIC2 gene codes for a surface glycoprotein that has been shown to be very strongly and reliably expressed in PNETs, but not in other small round blue cell tumors and not in small cell carcinoma of the lung. However, MIC2 expression has not been studied in MCC. We investigated the use of MIC2 analysis in the distinction of MCC from PNET. Five additional MCCs were stained with the monoclonal 12E7 antibody, ant one additional tumor showed the strong membranous positivity reported in PNETs. Our data suggest that MIC2 analysis may be useful in differentiating between MCC and PNET However, cases will remain for which the distinction is elusive and cytogenetic analysis may be helpful.