Machine Learning-Supported Diagnosis of Small Blue Round Cell Sarcomas Using Targeted RNA Sequencing

Small blue round cell sarcomas (SBRCSs) are a heterogeneous group of tumors with overlapping morphologic features but markedly varying prognosis. They are characterized by distinct chromosomal alterations, particularly rearrangements leading to gene fusions, whose detection currently represents the most reliable diagnostic marker. Ewing sarcomas are the most common SBRCSs, defined by gene fusions involving EWSR1 and transcription factors of the ETS family, and the most frequent non-EWSR1-rearranged SBRCSs harbor a CIC rearrangement. Unfortunately, currently the identification of CIC::DUX4 translocation events, the most common CIC rearrangement, is challenging. Here, we present a machine-learning approach to support SBRCS diagnosis that relies on gene expression profiles measured via targeted sequencing. The analyses on a curated cohort of 69 soft-tissue tumors showed markedly distinct expression patterns for SBRCS subgroups. A random forest classifier trained on Ewing sarcoma and CIC-rearranged cases predicted probabilities of being CIC-rearranged >0.9 for CIC-rearranged-like sarcomas and <0.6 for other SBRCSs. Testing on a retrospective cohort of 1335 routine diagnostic cases identified 15 candidate CIC-rearranged tumors with a probability >0.75, all of which were supported by expert histopathologic reassessment. Furthermore, the multigene random forest classifier appeared advantageous over using high ETV4 expression alone, previously proposed as a surrogate to identify CIC rearrangement. Taken together, the expression-based classifier can offer valuable support for SBRCS pathologic diagnosis.

CIC-Rearranged Sarcoma

CIC-rearranged sarcoma is a rare type of small round cell sarcoma. The tumors often affect the deep soft tissues of patients in a wide age range. They are highly aggressive, respond poorly to chemotherapy, and have a worse outcome than Ewing sarcoma. CIC-rearranged sarcoma has characteristic and recognizable histology, including lobulated growth, focal myxoid changes, round to epithelioid cells, and minimal variation of nuclear size and shape. Nuclear ETV4 and WT1 expression are useful immunohistochemical findings. CIC fusion can be demonstrated using various methods; however, even next-generation sequencing suffers from imperfect sensitivity, especially for CIC::DUX4.

A Practical Approach to Small Round Cell Tumors Involving the Gastrointestinal Tract and Abdomen

Small round cell neoplasms are diagnostically challenging owing to their clinical and pathologic overlap, necessitating use of large immunopanels and molecular analysis. Ewing sarcomas (ES) are the most common, but EWSR1 is translocated in several diverse neoplasms, some with round cell morphology. Molecular advances enable classification of many tumors previously termed 'atypical ES'. The current WHO Classification includes two new undifferentiated round cell sarcomas (with CIC or BCOR alterations), and a group of sarcomas in which EWSR1 partners with non-Ewing family transcription factor genes. This article reviews the spectrum of small round cell sarcomas within the gastrointestinal tract and abdomen.

Renal CIC-LEUTX rearranged sarcoma with multiple pulmonary metastases: a case report and literature review

BACKGROUND

CIC-rearranged sarcomas (CRS) are a group of heterogeneous tumors which mostly occur in the soft tissues of limbs and trunk, and are highly invasive with poor prognosis. Here, we describe a rare case of CRS that occurred in the left kidney with a CIC-LEUTX rearrangement.

CASE PRESENTATION

A 45-year-old male was admitted to hospital with a dry cough for more than two months without obvious cause. Physical examination and laboratory tests revealed no notable abnormality. The CT scan demonstrated a mass in the left kidney and multiple nodules in both lungs. The percutaneous core needle biopsy showed similar histomorphology and immunophenotype of small round cell malignant tumors. Genetic test revealed a CIC-LEUTX gene fusion.

CONCLUSIONS

We present a rare primary renal CRS with multiple pulmonary metastases, and LEUTX is confirmed as the fusion partner of CIC gene for the first time in a renal case.

CIC-rearranged sarcoma presenting with superior vena cava syndrome: case report

CIC-rearranged sarcomas are rare mesenchymal neoplasms belonging to the family of undifferentiated small round cell sarcomas. This report details the case of a 45-year-old man presenting with symptoms of mediastinal compression, radiological diagnosis of a mediastinal mass and rapid evolution to full-blown superior vena cava syndrome. The emergency was successfully managed with a pharmacological approach. Formulation of a pathological diagnosis of CIC-rearranged sarcoma was initially supported by fluorescence in situ hybridisation findings and later validated by next-generation sequencing, which showed CIC-DUX4 gene fusion. A chemotherapy regimen was started with immediate benefits for the patient. The spectrum of pathological entities able to cause superior vena cava syndrome is wide, and recognition of rare causes is important to tailor the therapeutic approach to the specific disease. This is, to the best of our knowledge, the first report of CIC-rearranged sarcoma presenting with superior vena cava syndrome.

A global collaboRAtive study of CIC-rearranged, BCOR::CCNB3-rearranged and other ultra-rare unclassified undifferentiated small round cell sarcomas (GRACefUl)

BACKGROUND

Undifferentiated small round cell sarcomas (URCSs) represent a diagnostic challenge, and their optimal treatment is unknown. We aimed to define the clinical characteristics, treatment, and outcome of URCS patients.

METHODS

URCS patients treated from 1983 to 2019 at 21 worldwide sarcoma reference centres were retrospectively identified. Based on molecular assessment, cases were classified as follows: (1) CIC-rearranged round cell sarcomas, (2) BCOR::CCNB3-rearranged round cell sarcomas, (3) unclassified URCSs. Treatment, prognostic factors and outcome were reviewed.

RESULTS

In total, 148 patients were identified [88/148 (60%) CIC-rearranged sarcoma (median age 32 years, range 7-78), 33/148 (22%) BCOR::CCNB3-rearranged (median age 17 years, range 5-91), and 27/148 (18%) unclassified URCSs (median age 37 years, range 4-70)]. One hundred-one (68.2%) cases presented with localised disease; 47 (31.8%) had metastases at diagnosis. Male prevalence, younger age, bone primary site, and a low rate of synchronous metastases were observed in BCOR::CCNB3-rearranged cases. Local treatment was surgery in 67/148 (45%) patients, and surgery + radiotherapy in 52/148 (35%). Chemotherapy was given to 122/148 (82%) patients. At a 42.7-month median follow-up, the 3-year overall survival (OS) was 92.2% (95% CI 71.5-98.0) in BCOR::CCNB3 patients, 39.6% (95% CI 27.7-51.3) in CIC-rearranged sarcomas, and 78.7% in unclassified URCSs (95% CI 56.1-90.6; p < 0.0001).

CONCLUSIONS

This study is the largest conducted in URCS and confirms major differences in outcomes between URCS subtypes. A full molecular assessment should be undertaken when a diagnosis of URCS is suspected. Prospective studies are needed to better define the optimal treatment strategy in each URCS subtype.

[Clinical and morphological characteristics of Ewing's sarcoma and the algorithm for diagnosing undifferentiated round cell sarcomas]

BACKGROUND

The group of undifferentiated round cell sarcomas, according to the World Health Organization Classification, in addition to Ewing's sarcoma (ES), includes round cell sarcoma with rearrangement of the EWSR1 gene with partners not from the ETS gene family, sarcoma with BCOR gene alterations, CIC -rearranged sarcoma. Despite the fact that all tumors have clear histological and immunological criteria, their diagnosis can be difficult, given the fact that there are overlapping variants of the morphological picture and immunophenotype both within the group and with other round cell tumors.

OBJECTIVE

Present a comparative analysis of genetically verified ES, sarcoma with BCOR gene alterations and CIC-rearranged sarcoma.

MATERIAL AND METHODS

A comparative study of biopsy specimens of bones, soft tissues and internal organs was carried out in 118 patients with ES, 10 with BCOR gene alterations and 8 with CIC-rearranged sarcomas. All cases were genetically verified. The following research methods were used: histological, immunohistochemical, RT-PCR, RNA sequencing and FISH.

RESULTS

Within our cohort, it was shown that ES predominantly affects bones, while soft tissue localization is more typical for the other two undifferentiated round cell sarcomas. Histologically, in the overwhelming majority of cases, ES is characterized by a monomorphic round-cell structure; on the contrary, heterogeneous structure is typical for sarcoma with alterations of the BCOR gene, CIC-rearranged sarcoma. High sensitivity and specificity of CD99/NKX2.2 co-expression for ES, BCOR/SATB2/TLE1 for sarcoma with BCOR gene alterations, high specificity and low sensitivity of WT1/ETV4 co-expression for CIC-rearranged sarcoma was shown.

CONCLUSION

For the differential diagnosis of undifferentiated round-cell sarcomas, it is necessary to take into account the clinical, morphology when compared with the data of the IHC study, and verification by molecular genetic methods is necessary to improve the accuracy of diagnosis.

[CIC-rearranged sarcoma with rhabdoid features: a clinicopathological analysis]

Objective: To investigate the histopathologic, immunohistochemical, molecular genetic characteristics of CIC-rearranged sarcoma (CRS) with rhabdoid features. Methods: The clinical and pathologic data of two cases of CRS diagnosed between 2019 and 2021 at the Department of Pathology, Jiangsu Province Hospital were analyzed. Immunohistochemical study and fluorescence in situ hybridization (FISH) were performed. The relevant literature was reviewed. Results: Both patients were female, one was 58 years old, with tumor located in left thigh; the other was 43 years old, with tumor located in left pelvic cavity. Microscopically, both tumors were composed of small to medium-sized round, oval cells, arranged in nodules or sheets. The tumor cells showed irregular nuclear outline, coarse chromatin with prominent nucleoli and brisk mitotic activity. Both cases showed rhabdoid phenotype with myxoid stromal changes. Immunohistochemically, both cases were positive for CD99 and c-myc. High WT1 reactivity was seen in classic area, with low reactivity in rhabdoid area. There was no INI1 lost in both cases. Both were negative for NKX2.2 and NKX3.1. By FISH both cases demonstrated convincing break-apart signals of CIC gene. One patient died of disease after 1 month, and the other died of disease after 3 months. Conclusions: CRS is a small round cell undifferentiated sarcoma of the bone and soft tissue defined by molecular genetic characteristics, and may show atypical morphologic and immunophenotypic characteristics such as rhabdoid features. A correct understanding of its rare morphologic and immunophenotypic characteristics, combined with molecular pathologic detection, is conducive to correct diagnosis.

Bone lesions - diagnostic approach using immunohistochemistry and molecular pathology

Immunohistochemistry and molecular pathology play an essential role in the diagnosis of some focal bone lesions. These techniques may greatly help to distinguish primary bone tumors from metastatic diseases and allow a biologically important refinements in subclassification of round cell sarcomas. Recently, the diagnostic accuracy of organ and tumor specific antibodies has improved significantly. Knowledge of new type of antibodies and their meaningful use enables an accurate classification of the most undifferentiated carcinomas of unknown primary. However, the interpretation of immunohistochemical stains and molecular genetic analysis can be difficult in bone biopsies due to previous decalcification. This article summarizes the most important algorithmic approach to the diagnosis of bone tumors. It outlines the most frequently used tissue-specific antibodies. New advances in the understanding of bone tumorigenesis are also discussed.

DNA Methylation Profiling for Diagnosing Undifferentiated Sarcoma with Capicua Transcriptional Receptor (CIC) Alterations

Undifferentiated soft tissue sarcomas are a group of diagnostically challenging tumors in the pediatric population. Molecular techniques are instrumental for the categorization and differential diagnosis of these tumors. A subgroup of recently identified soft tissue sarcomas with undifferentiated round cell morphology was characterized by Capicua transcriptional receptor (CIC) rearrangements. Recently, an array-based DNA methylation analysis of undifferentiated tumors with small blue round cell histology was shown to provide a highly robust and reproducible approach for precisely classifying this diagnostically challenging group of tumors. We describe the case of an undifferentiated sarcoma of the abdominal wall in a 12-year-old girl. The patient presented with a voluminous mass of the abdominal wall, and multiple micro-nodules in the right lung. The tumor was unclassifiable with current immunohistochemical and molecular approaches. However, DNA methylation profiling allowed us to classify this neoplasia as small blue round cell tumor with CIC alterations. The patient was treated with neoadjuvant chemotherapy followed by complete surgical resection and adjuvant chemotherapy. After 22 months, the patient is disease-free and in good clinical condition. To put our experience in context, we conducted a literature review, analyzing current knowledge and state-of-the-art diagnosis, prognosis, and clinical management of CIC rearranged sarcomas. Our findings further support the use of DNA methylation profiling as an important tool to improve diagnosis of non-Ewing small round cell tumors.

CIC fusion-positive sarcoma of the spermatic cord

In addition to germ cell tumors and tumors of the sex cord stroma, the WHO classification of testis and paratesticular tumors also contains malignant soft tissue tumors. Among them, liposarcomas of the spermatic cord are the most common entities. Other mesenchymal tumors with smooth muscle, skeletal muscle, fibroblastic/myofibroblastic, or nerve sheath differentiation are rare. Ewing sarcoma is composed of uniform small round cells and typically characterized by translocations of the EWSR1 gene. In rare cases, Ewing sarcoma-like tumors lack an EWSR1 gene fusion. Some of these tumors harbor a specific CIC translocation. However, Ewing-like sarcoma has up to now never been described in the testis or spermatic cord. The present case describes the first EWSR1-negative, undifferentiated round cell sarcoma with CIC translocation of the spermatic cord. Potential differential diagnoses are discussed.

[What´s new in Ewing-like sarcoma family? Soft tissue and bone sarcomas with CIC/BCOR rearrangement. Review of the literature and first personal experience]

The literature is reviewed regarding of a rare molecularly defined group of sarcomas with rearrangement of both CIC and BCOR genes, which were originally placed into the EWSR1wt Ewing-like category. Personal experience with three cases demonstrating difficulties of this issue is added. Both groups of lesions differ not only by age and topography, but also vary in both the prognostic and the predictive parameters. CIC-rearranged tumors are very aggressive and almost never occur in the skeleton; in contrary, the BCOR-rearranged ones are predominantly bone tumors in young males behaving even better than classical Ewing sarcoma. From the morphologic point of view, it turned out to be a salient finding that these types of neoplasm might leave canonical morphotype of small blue round cell sarcoma. Instead of it, they are not uncommonly characterized as a relatively uniform spindle cell proliferation with prevailing myxoid transformation deserving much broader differential diagnosis. Our three cases reports display difficulties in reaching the correct diagnosis even by implementing sophisticated molecular techniques in routine practice. Notwithstanding of exhaustive molecular assays used, one may still encounter a lesion where original descriptive term Ewing-lie sarcoma remains uncorrected.

Small cell osteosarcoma of rib: diagnosis and treatment of the rare case

Small cell osteosarcomas are very rare tumors which are classified as the component of Ewing's sarcoma family. Although the tumor generally is seen on long bones, short bone involvement is rare. Moreover, rib localization is quite uncommon and to the best of our knowledge, only one case has been reported so far. Herein, we described a case of rib-localized small cell osteosarcomas which was only presented with localized left sided pain. Resection surgery followed by adjuvant chemotherapy was performed. Clinico-pathological features and therapeutic approach are discussed in the light of the relevant literature.

The small round blue cell tumors of the sinonasal area

The diagnostic classification of small round blue cell tumors of the sinonasal area to include diverse malignancies of epithelial, hematolymphoid, neuroectodermal, and mesenchymal origin is challenging to the surgical pathologist using conventional histopathologic approaches because the cytomorphologic features are often overlapping or indistinctive. Rare or occasional clinical presentations in atypical age groups or unusual locations, as well as small biopsy samples may further complicate the differential diagnosis. Immunohistochemistry represents an extensively investigated ancillary technique that may aid in the provision of a definitive diagnosis. In recent years, certain small round blue cell tumors have been shown by cytogenetic analysis to have specific and primary chromosomal alterations, providing clinicians with a valuable tool to enhance their diagnostic armamentarium. The addition of molecular cytogenetic [fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH)] and molecular pathologic [polymerase chain reaction (PCR) and reverse transcriptase (RT)-PCR] approaches has further enhanced the sensitivity and accuracy of detecting these genetic alterations including assessment in formalin-fixed, paraffin-embedded tissues. Establishing an accurate diagnosis of a small round blue cell tumor of the sinonasal tract frequently requires adjunctive studies including immunohistochemical and molecular analyses.

Intra-abdominal desmoplastic small round cell tumour in a 39-year-old man

Desmoplastic small round cell tumor is a very rare neoplasm, that usually appears in children and young adolescents. There is no standard therapy, and responses to chemotherapy are infrequent. Surgery is still the main treatment for this disease. We report the case of a 39 year-old man and briefly summarize the evidence about this tumor.

Successful treatment of a child with t(15;19)-positive tumor

A subset of poorly differentiated carcinomas is characterized by the translocation t(15;19)(q13;p13), resulting in a BRD4/NUT fusion gene. Typically, this tumor affects children or young adults, with a predilection for midline head and neck or thoracic structures. The clinical course is invariably fatal, in spite of intensive chemotherapy and radiotherapy. We here present the successful treatment of a 10-year-old boy who presented with a BRD4/NUT-positive undifferentiated tumor in the iliac bone. The patient was selected for combined modality therapy, and has remained in complete continuous remission for close to 13 years. The findings show that t(15;19)-BRD4/NUT-positive tumors may arise in locations more typical for other pediatric tumors, such as Ewing sarcoma, and that they not always display epithelial differentiation. More importantly, our results also demonstrate that at least some patients with t(15;19)-positive tumors may be successfully treated.

Pitfalls in the detection of t(11;22) translocation by fluorescence in situ hybridization and RT-PCR: a single-blinded study

The t(11;22) translocation is a diagnostic hallmark of various small round-cell tumors. This study correlates the performance of fluorescence in situ hybridization (FISH) and reverse transcription polymerase chain reaction (RT-PCR) in the detection of this translocation analyzing paraffin-embedded tissue specimens. As negative control samples, 10 cases of normal colon mucosa and 10 cases of colon carcinoma tissue were analyzed by FISH to determine a valid cutoff value for the diagnosis of a t(11;22) translocation. The mean number of false-positive nuclei differed significantly between disomic and polysomic control group cases (P=0.002). Therefore, the cutoff value was determined considering the pitfall polysomy. The analysis group consisted of 20 cases from the University of Düsseldorf and 10 cases from the University of Bonn. These cases were analyzed using PCR (Düsseldorf) and FISH (Bonn) using a single-blinded approach. Twenty-two cases (73.3%) were concordant in both methods. Five cases (16.7%) were discrepant, showing a positive result in FISH whereas PCR was negative. Three cases (10.0%) were analyzed by FISH, and PCR failed for nonoptimized tissue preparation. In conclusion, the detection of t(11;22) translocation is critically dependent on a thoroughly defined cutoff value for FISH and on appropriate tissue preparation for both methods. We recommend FISH as a sensitive screening tool in the detection of t(11;22) followed by subsequent PCR amplification of the specific chimeric transcript.

Recent advances in the molecular biology, diagnosis and novel therapies for various small blue cell tumors

Small blue cell tumors are a group of tumors that share a common histologic characteristic with H&E staining. This makes differentiation from one another difficult as they all appear small, blue and round. Even though they all appear the same, they are vastly different from each other. Several different techniques have been developed to help further delineate and classify these tumors which include: small cell lung cancer (SCLC); non-Hodgkin's lymphoma (NHL); Ewing's sarcoma; rhabdomyosarcoma; Merkel carcinoma; neuroblastoma; carcinoid tumors; and intra-abdominal desmpolastic small round cell tumor. Using immunoperoxidase staining, reverse transcriptase polymerase chain reaction and fluorescence in situ hybridization techniques, these tumors have been successfully differentiated from one another. This separation makes staging and treatment of these tumors more effective, as not all of these tumors respond to the same modality of treatment. The following review summarizes some of the recent findings in the various small blue cell tumors and with the potential of novel therapies.

Desmoplastic small round cell tumor presenting in the ovaries: report of a case and review of the literature

Desmoplastic small round cell tumor is a recently recognized clinical entity with specific morphologic, immunocytochemical, and genetic features. Though this tumor is mostly described to involve serosal surfaces, we report a case with ovarian involvement. The clinical presentation and differential diagnoses as well as the treatment including aggressive surgical debulking and multiagent chemotherapy are discussed.

Practical application of molecular genetic testing as an aid to the surgical pathologic diagnosis of sarcomas: a prospective study

The strong correlation of specific reciprocal translocations with individual tumor types and the demonstration that polymerase chain reaction (PCR)-based methods can detect translocations in tissue samples have stimulated interest in the role of molecular genetic testing in diagnostic surgical pathology. To evaluate the clinical utility of PCR-based molecular analysis of soft tissue neoplasms in routine surgical pathology, 131 consecutive soft tissue tumors submitted for molecular genetic testing at a tertiary care teaching hospital were prospectively analyzed over a 36-month period. RT-PCR was used to test tumor RNA for fusion transcripts characteristic of malignant round cell tumors (including Ewing sarcoma/primitive neuroectodermal tumor, desmoplastic small round cell tumor, and alveolar rhabdomyosarcoma), spindle cell tumors (including synovial sarcoma and congenital fibrosarcoma), and fatty tumors (myxoid liposarcoma). DNA sequence analysis was used to confirm the identity of all PCR products, and the PCR results were compared with the histopathologic diagnosis. We found that sufficient RNA for RT-PCR-based testing was recovered from 96% of the 131 cases and the percentage of tumors that tested positive for the associated characteristic fusion transcript was in general agreement with those reported in the literature. DNA sequence analysis of PCR products identified both variant transcripts and spurious PCR products, underscoring the value of product confirmation steps when testing formalin-fixed, paraffin-embedded tissue. Only in rare cases did testing yield a genetic result that was discordant with the histopathologic diagnosis. We conclude that PCR-based testing is a useful adjunct for the diagnosis of malignant small round cell tumors, spindle cell tumors, and other miscellaneous neoplasms in routine surgical pathology practice.

Subgrouping and grading of soft-tissue sarcomas by fine-needle aspiration cytology: a histopathologic correlation study

To evaluate the accuracy and reproducibility of subgrouping and grading soft-tissue sarcomas by fine-needle aspiration biopsy (FNAB), a blind review was conducted of 84 FNAB specimens from 77 malignant and 7 benign soft-tissue lesions. Cytomorphologic subgroups included 31 spindle-cell, 24 pleomorphic, 11 myxoid, 7 epithelioid/polygonal, 3 small round cell, and 8 nondiagnostic cases. Malignancies included one lymphoma and 41 primary, 15 recurrent, and 20 metastatic soft-tissue sarcomas. Adequacy was defined as a majority of slides with at least 5 clusters of 10 unobscured cells. Five originally false-negative cases were considered nondiagnostic on review. Sarcoma was recognized in 59 of 64 adequate cases (92%) with available histology; however, the specific histopathologic subtype was identified in only 9 cases (14%). Benign myxoid and spindle-cell lesions were difficult to separate from low-grade sarcomas in 4 cases, and a B-cell lymphoma with sclerosis mimicked a low-grade myxoid sarcoma. The assigned cytologic grade accurately reflected the histologic grade in 90% of sarcomas when segregated into high and low grades. Pleomorphic, small round cell, and epithelioid/polygonal subgroups corresponded to high-grade sarcomas in all cases with only minor noncorrelations. Major grading noncorrelations occurred in 50% of myxoid and 9% of spindle-cell sarcomas. Therefore, attention should be given to specimen adequacy, and caution should be exercised when attempting to grade myxoid and spindle-cell sarcomas by FNAB.

Use of reverse transcriptase polymerase chain reaction for diagnosis and staging of alveolar rhabdomyosarcoma, Ewing sarcoma family of tumors, and desmoplastic small round cell tumor

PURPOSE

To compare the use of reverse transcriptase polymerase chain reaction (RT-PCR) with that of morphology-based methods for diagnosis, staging, and detection of metastatic disease in pediatric alveolar rhabdomyosarcoma (ARMS), Ewing sarcoma family of tumors (ESFT), and desmoplastic small round cell tumors (DSRCT).

MATERIALS AND METHODS

RT-PCR assays for the EWS-FLII, EWS-ERG, PAX3-FKHR, PAX7-FKHR, and EWS-WTI fusion transcripts were performed on RNA extracted from the primary tumor tissue, bone marrow, and body fluids obtained at initial presentation and relapse. Molecular findings were compared with original histologic diagnoses and results of staging procedures.

RESULTS

Eighty-eight samples from 47 patients with ARMS (n = 13), ESFT (n = 31), or DSRCT (n = 3) were analyzed. The detection rate of metastatic disease was significantly higher with RT-PCR (95%) as compared with the morphologic methods (70%) for the three pediatric sarcomas studied. In primary tumors with characteristic fusion transcript, RT-PCR was positive in all cases with morphologic evidence of metastatic disease. Moreover, in six patients (3 with ARMS, 2 with DSRCT, and 1 with ESFT) with metastatic disease, micrometastases in bone marrow (4) and other sites (2) were detected by RT-PCR alone. Importantly, none of the patients with localized disease diagnosed had micrometastases detected by RT-PCR in bone marrow.

CONCLUSIONS

The high sensitivity and specificity of RT-PCR for the characteristic fusion transcripts of pediatric sarcomas make it an ideal method to aid in the routine staging of these patients. In addition, the 100% sensitivity of RT-PCR in detection of micrometastasis makes it useful for follow-up and detection of minimal residual disease. However, the clinical significance of molecularly-detectable disease remains unknown. Further studies should aim to elucidate the therapeutic and prognostic implications of micrometastases detected by RT-PCR alone.

Diagnosis, treatment and outcome of patients with Askin-tumors

Askin tumors are highly malignant small-round-cell tumors of the thoracopulmonary region, which occur rarely. Therefore, we report on our experiences with eight patients (5 male, 3 females), who were treated in our department between 11'94 and 10'97 (age: 9-40 years, mean age: 20.5 years). All Askin tumors were diagnosed by histological and immunohistochemical examinations as well as molecular genetic proof of characteristic translocations. In all patients, the tumor arose from the chest wall, infiltrating adjacent ribs and parts of the lung. At the time of first diagnosis, five patients did not reveal any metastases. One patient suffered from intrapulmonary metastases and two patients from an infiltration of the diaphragm and of adjacent vertebral bodies. Treatment consisted of a pre- and postoperative (radio-) chemotherapy according to the EVAIA protocol and a radical tumor resection in all patients. The postoperative course was uneventful in seven patients, one patient suffered from pneumonia after multiple wedge resections for intrapulmonary metastases. Four patients, in whom primary tumor resection was complete, are alive 14, 20, 35 and 84 months after first diagnosis - only one patient had to undergo a second operation for a local relapse 17 months after first diagnosis. The other 4 patients, who suffered from a very extensive primary tumor, expired 13, 17, 18 and 39 months after the diagnosis was made. Our data demonstrate that Askin tumors require an aggressive multimodality treatment consisting of pre- and postoperative chemotherapy, radical surgical resection and postoperative irradiation, which may be performed preoperatively in selected cases, too.

Clinically critical impact of molecular genetic studies in pediatric solid tumors

BACKGROUND

Standard cytogenetic techniques are time-consuming and often not informative with solid tumors. In contrast, the reverse transcriptase-polymerase chain reaction (RT-PCR) is a readily available technique that can rapidly detect tumor-specific chromosomal rearrangements, even in small biopsy specimens. We present cases depicting the importance of including molecular diagnostic studies in the routine evaluation of pediatric solid tumors.

PROCEDURE

We used RT-PCR to detect chimeric transcripts specific for major pediatric solid tumors, including peripheral primitive neuroectodermal tumor (pPNET), alveolar rhabdomyosarcoma (ARMS), and desmoplastic small round-cell tumor (DSRCT). We reviewed six recent cases in which the initial diagnosis was changed by the results of RT-PCR.

RESULTS

Highly unusual or nonspecific clinical and/or histopathologic findings led to the initial diagnoses of neuroblastoma in three patients and DSRCT, leukemia, and carcinoma in one patient each. The final diagnoses after RT-PCR studies were pPNET in three patients, ARMS in two patients, and DSRCT in one patient. RT-PCR results led to early corrections in the diagnosis in two patients, but four patients received treatment not considered optimal for the neoplasms ultimately diagnosed, including three who, despite presenting with localized tumors that have a >70% cure rate with standard therapy, have died or are dying of disease.

CONCLUSIONS

Molecular genetic studies on solid tumors can clarify the diagnosis in seemingly straightforward as well as in overtly problematic cases. These diagnostic distinctions are now critical as disease-specific and risk-directed therapies have emerged.

Synovial sarcoma mimicking desmoplastic small round-cell tumor: critical role for molecular diagnosis

BACKGROUND

The identification of recently described nonrandom chromosomal defects specific for various small round-cell and spindle-cell sarcomas can eliminate diagnostic uncertainty arising from the clinical and histopathologic overlap of soft tissue neoplasms.

METHODS

A 26-year-old man presented with bulky abdominal-pelvic disease. Immunohistochemical and molecular studies on tumor were performed. Treatment was instituted using cycles of high-dose cyclophosphamide (4,200 mg/m2) with doxorubicin (75 mg/m2).

RESULTS

Clinical findings pointed to desmoplastic small round-cell tumor. The tumor was histologically undifferentiated and immunoreactive for vimentin but negative for other markers. Reverse transcriptase-polymerase chain reaction revealed the SYT/SSX2 fusion transcript of the synovial sarcoma t(X;18) chromosomal rearrangement. The high-dose chemotherapy, plus surgery, achieved a complete remission, but recurrent disease emerged 13 months from diagnosis.

CONCLUSIONS

This clinically unique case of synovial sarcoma highlights how the use of now readily available molecular techniques will allow more accurate appraisals of the incidence and anatomic distribution of soft tissue neoplasms-information that bears upon pathogenesis and treatment. This case confirms the utility of high-dose alkylator-based therapy for synovial sarcoma. It also demonstrates that with nonlocalized solid tumors, the eradication of minimal residual disease remains an elusive goal. One alternative involves immunologic attack against markers derived from tumor-specific chromosomal defects such as those found in our patient.

[A resected case of malignant peripheral nerve sheath tumor (MPNST) necessary to distinguish from Askin tumor]

We have treated a patient with malignant peripheral nerve sheath tumor (MPNST) for 7 years by interdisciplinary therapy. The diagnosis and treatment are reported with the clinical course so far. A 20-year-old man underwent surgical resection of a tumor on the left side of the chest in 1990, and a diagnosis of Askin tumor was made. In 1993, the disease recurred in the left axilla and was surgically resected. The surgical specimen was investigated histologically, and a diagnosis of MPNST was made instead of Askin tumor. Recently, a tumor began to grow in the left pleural cavity and was surgical resected. The tumor tissue contained both cells with oval and long spindle nuclei, which were intermingled with each other. Immunohistochemically, the tumor cells were positive for vimentin and some of them were positive for S100 protein. Because electron microscopy showed cytoplasmic processes on the tumor cell and basal lamina-like structures, a diagnosis of recurrent MPNST was made. Because this lesion resembled Askin tumor in its clinical manifestations and histological characteristics, differential diagnosis from Askin tumor was necessary. When a malignant soft tissue tumor arising from the mediastinum or chest walls is detected, immunohistochemical and electron microscopic studies should be performed. The diagnosis should be based on the overall findings including the location and clinical data.

Small round-cell type of malignant peripheral nerve sheath tumor

Five cases of primitive, small, round-cell tumor that are a type of hitherto unclassified neurogenic sarcoma are described. The tumors were located deep within the soft tissue of the trunks and limbs without association with major nerves. The histologic features consisted mainly of uniform, small, round, tumor cells with scanty cytoplasm. Foci of uniform, short, spindle-shaped tumor cells arranged in whorl-like patterns were observed in some areas. Although the immunoreactivity for the neural markers, Leu-7 and MIC-2, was not marked, cell processes and fragmentous basal laminae, which are ultrastructural neural features, were found in both spindle-shaped and round tumor cells. In four cases, EWS chimeric transcripts were analyzed by reverse-transcription polymerase chain reaction. EWS chimeric mRNA (EWS-FLI-1, EWS-ERG, EWS-E1AF, EWS-ETV1, EWS-FEV) was not detected in any cases. The tumors were not consistent with peripheral primitive neuroectodermal tumor. We propose them as a small round-cell type of MPNST that might differentiate toward the immature neural cells.

Diagnosis and differential diagnosis of small-cell lesions of the liver

The objective of this study was to evaluate the cytologic spectrum of small cell lesions of liver as diagnosed by fine-needle aspiration (FNA). Of 304 FNAs of liver that were performed in our institution between 1990 and 1994, 29 were classified as small-cell lesions. The final diagnoses were as follows: small-cell undifferentiated carcinoma (10), neuroendocrine carcinoma (9), cloacogenic carcinoma (1), Merkel-cell carcinoma (1), cholangiocarcinoma (1), metastatic adenocarcinoma (4), small-cell sarcoma (1), lymphoma (2). Relevant clinical history and immunocytochemistry were helpful in making the final diagnosis in some cases. The diagnosis and differential diagnosis of small cell lesions of the liver are discussed in detail in this report.

[Small-cell sarcoma of the esophagus as a fourth malignancy. Its palliative therapy with argon gas coagulation]

HISTORY

A prostatic carcinoma, an early gastric carcinoma and a colon carcinoma had occurred over 15 years in a now 82-year-old patient. He was now admitted because of severe dysphagia.

INVESTIGATIONS

Gastroscopy revealed an exophytic tumour of the oesophagus, histologically identified as a small-cell sarcoma. It had caused a 12 cm long severe eccentric stenosis of the oesophagus. Tissue from the previous three tumours were examined immunohistochemically for p-53 gene mutation, but only the oesophageal sarcoma gave positive results.

TREATMENT AND COURSE

After part of exophytic tumour had been ablated by argon gas coagulation a prosthetic tube was implanted. Bleeding from erosion of a large metastasis in the gastric fundus was successfully treated by argon gas coagulation 4 months after the previous discharge, but the patient died of the malignancy 1/1 and half months later.

CONCLUSIONS

The consecutive occurrence of four different malignant tumours is rare even in advanced age. In this case the malignancies were presumably unrelated and it demonstrates the possibility of removing an eccentric tumour stenosis by argon gas coagulation before implanting a prosthesis.

Ca125 and neuron-specific enolase (NSE) as tumour markers for intra-abdominal desmoplastic small round-cell tumours

Seven consecutive patients with intra-abdominal desmoplastic small round-cell tumours were screened at presentation for carcinoembryonic antigen (CEA), Ca19-9, Ca15-3, Ca125, alpha-fetoprotein (AFP), human chorionic gonadotrophin (hCG) and neuron-specific enolase (NSE). Initially elevated tumour markers were used to monitor therapy and follow-up. Tumour marker assays were all in the normal range, with the exception of Ca125 and NSE. The Ca125 level was initially high in six of the seven patients (86%) with a median value of 200 U ml-1 and a range of 22-735 U ml-1. The NSE value was elevated before therapy in three of the five patients (60%) for whom assay results were available, with a median of 19 ng ml-1 and a range of 6.8-37.5 ng ml-1 . Ca1 25 normalized in five out of six cases and NSE always normalized during chemotherapy, but neither of these two tumour markers correlated specifically with response, as only one patient experienced a partial response, five tumour stabilization and the remaining patient tumour progression. At progression, Ca125 was again elevated in two out of four cases several weeks before clinical relapse and NSE in only one out of three cases. Ca125 and NSE are frequently raised in the serum of patients with intra-abdominal desmoplastic small round-cell tumours before therapy, but are not reliable monitors of the course of the disease. However, normalization is frequently associated with an improvement of symptoms or a moderate clinical response.

Differentiating small round cell sarcomas of the soft parts by an innovative immunogold labeling method: an ultrastructural study

A new immunoelectron microscopy procedure was developed by remaking the fixed-frozen tissue specimens into LR White resin blocks suitable for postembedding colloidal gold immunolabeling, and used to examine 16 cases of small round cell soft tissue sarcomas. In rhabdomyosarcoma, ultrastructural double-immunogold staining demonstrated a coexpression of muscle specific actin and desmin in the same tumor cell. In both Ewing's sarcoma and peripheral neuroepithelioma, the heterogeneous expression of MIC2 gene product (p30/32MIC2) in each tumor cell was demonstrated as well. In peripheral neuroepithelioma, the colloidal gold immunolabeling for neurofilament demonstrated the intermediate filaments surrounding microtubules. The procedure for ultrastructural colloidal gold immunolabeling using fixed-frozen tissue is thus considered to be useful not only for tumor diagnosis, but also for investigating various subcellular structures.

Appraisal of the comparative utility of immunohistochemistry and electron microscopy in the diagnosis of childhood round cell tumors

To provide an objective assessment of the comparative utility of fluorescence- and peroxidase-based immunohistochemistry and electron microscopy, an observer blinded study was conducted under realistic study conditions utilizing a large sampling of poorly differentiated pediatric round cell tumors. Working independently, using a single ancillary technique of particular expertise, each of three investigators attempted to render a specific diagnosis with regard to 50 diagnostically challenging tumors. The results were compared against the subsequent "file diagnosis" established by consensus with all relevant information made available. A grading scheme was applied wherein points were awarded based on the accuracy and confidence of diagnosis. A comparative efficiency rating, expressed as a percentage, was formulated by dividing the number of points awarded each technique by the total number of points theoretically available. Electron microscopy proved superior overall, with an efficiency rating of 89%. Immunoperoxidase and immunofluorescence studies yielded efficiency ratings of 71 and 61%, respectively. Used in combination, the techniques achieved an efficiency rating of 95%. Application of these ancillary techniques resulted in a revision of the provisional diagnosis in 11 of 50 cases, and left only two cases without a firm specific diagnosis.

Soft tissue small round cell tumors: morphological parameters

Soft tissue small round cell tumors (SRCTs) comprise a heterogeneous group of neoplasms that predominate in childhood and adolescence and share similar morphological features, consisting of dense cellular proliferation of small round cells with a primitive appearance. Rhabdomyosarcomas, peripheral neuroepitheliomas, Ewing's sarcomas, and lymphomas/leukemias are the prototypic SRCT; other recently described tumors that should be added to the list are the desmoplastic SRCT and the rhabdoid tumor of soft tissues. In addition, several other primary soft tissue neoplasms and metastatic tumors have occasionally been considered in the differential diagnosis of SRCT. The precise identification of a given SRCT is important because of its clinical relevance. However, it may be difficult because the diagnostic criteria are sometimes subtle and several histologic and immunohistochemical features are not specific and/or may be simulated by different tumor types. We discuss the morphological clues that in our opinion are most useful for their diagnosis, the criteria for distinguishing between peripheral neuroepithelioma and Ewing's sarcoma, and the main diagnostic pitfalls.

Small round blue cell tumors in bone: prognostic factors correlated to Ewing's sarcoma and neuroectodermal tumors

Ewing's sarcoma and peripheral neuroectodermal tumors are the most common small round blue cell tumors of bone. Accurate prognostic factors are required to define guidelines to standardize the treatment modalities and to adapt these modalities to the potential evolution of the disease. The various factors that have emerged in the literature as influences on the outcome of patients with Ewing's sarcoma or peripheral neuroectodermal tumors of bone are considered in this review. The presence of metastases at the clinical onset of the disease represents the most adverse prognostic factor. For nonmetastatic patients, axial location appears to be the most unfavorable factor, despite initial tumor volume, by showing that the tumor burden could be a more appropriate indicator of patient outcome. The importance of a local control of the disease by surgery has been emphasized, and the value of the histopathologic evaluation of the response to chemotherapy has been stressed.

Differential diagnosis of small round cell tumors

The differential diagnosis of small round cell tumors includes not only the small round cell tumors of infancy and childhood, but a variety of mesenchymal, cutaneous, and lymphoreticular neoplasms that may occur in adults as well as children. Moreover, lesions considered to be the classical small round cell tumors of childhood may occasionally occur in adults, and lesions characteristically seen in adults may at times occur in children. An awareness of the diverse lesions that may present as small round cell tumors is critical to arrive at the correct diagnosis. Immunohistochemical techniques and ultrastructural studies have now become indispensable in the diagnosis of small round cell tumors. With recent developments in cytogenetic and molecular genetic techniques, the pathologist has acquired an even more powerful and precise armamentarium of diagnostic tools. Judicious use of these methods, with knowledge of their significance and limitations, is the responsibility of the pathologist and laboratory coworkers who play a pivotal role in patient care and treatment. The differential diagnosis of small round cell tumors, including adult-type sarcomas, lymphoreticular malignancies, and neuroectodermal tumors of skin and viscera that simulate classical small round cell tumors, is briefly reviewed with this perspective. Specific cytogenetic and molecular markers are covered in addition to the typical immunohistochemical and ultrastructural features of several diverse lesions.

Desmoplastic small round cell tumor

Desmoplastic small round cell tumor is an undifferentiated tumor associated with serosal surfaces, especially the peritoneum. It is found predominantly in adolescents and young adults and is much more common in males than in females. The tumor has a characteristic histology, with extensive stromal tissue around islands of small and undifferentiated cells revealing the desmoplastic appearance. The coexpression of epithelial and mesenchymal antigens distinguishes this entity from other small round and blue cell tumors of this age group. Cytogenetic studies showed a t(11;22) translocation that differs from the Ewing's tumor translocation and seems to be specific to this entity. The involvement of the WT1 and EWS genes in the translocation makes this tumor an interesting subject for research on histogenesis and differentiation in small round and blue cell tumors.

Postmenopausal intra-abdominal desmoplastic small cell tumor

Intra-abdominal desmoplastic small cell tumor (DSCT) usually occurs in infants and young male adults. A case of DSCT occurring in a 60 year old female is described. No other apparent primary origin was detected. A mesocolon tumor, measuring 23 x 12 x 10 cm, was composed predominantly of round to spindle cells which showed epithelioid- and focally sarcomatous arrangements. Immunohistochemically, the tumor cells showed perinuclear dot-like staining of CAM5.2, many cells expressed HHF35, and some cells contained vimentin, epithelial membrane antigen, desmin, alpha-smooth muscle actin, neuron-specific enolase, or Leu 7. Electron microscopic examination showed that the tumor cells had mesenchymal-fibroblastic features. The tumor had an aneuploid DNA content with high S-phase fraction. The patient, who was treated with adjuvant chemotherapy, was alive, having had three recurrences in 36 months. In the second and third recurrent lesions, increased cellular atypia and fascicular arrangements of spindle cells were observed. DSCT should be included in differential diagnoses of post-menopausal pelvic tumors which show light-microscopically and immunohistochemically divergent phenotypes.

Detection of the EWS/WT1 gene fusion by reverse transcriptase-polymerase chain reaction in the diagnosis of intra-abdominal desmoplastic small round cell tumor

We report two cases of intra-abdominal desmoplastic small round cell tumor with characteristic clinical, histological, immunohistochemical, and ultrastructural features. Fusion of the EWS gene on chromosome 22 and the WT1 gene on chromosome 11, resulting from the chromosomal translocation t(11;22)(p13;q12), was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in both cases. This translocation has been previously reported in this type of tumor using either cytogenetic or molecular biological techniques. Tumor tissue from both cases revealed no chimeric fusion transcripts characteristic of the Ewing sarcoma family of peripheral primitive neuroectodermal tumors or of alveolar rhabdomyosarcoma, two tumors in the differential diagnosis of intra-abdominal desmoplastic small round cell tumor. This report demonstrates the utility of molecular studies as an adjunct in the diagnosis of this rare and aggressive tumor.

Fine needle aspiration cytologic findings in malignant small cell tumor of the thoracopulmonary region (Askin tumor)

From 1980 to 1992, five cases of Askin tumor were diagnosed by fine needle aspiration cytology at the Shiraz University Hospitals, Namazi, Faghihi and Beheshti, Iran. All patients were female, their ages ranging between 15 and 22 years. Three of them had a mass on the right side and two on the left side of the chest. Chest roentgenography revealed no bone involvement. Two tumors involved the lungs and pleura. Urinary catecholamine levels were within normal limits. The fine needle aspiration smears revealed many small, round malignant cells with indistinct cytoplasm, a high nuclear/cytoplasmic ratio and prominent, multiple nucleoli. Homer-Wright rosettes were seen frequently. The cells were often arranged in rows simulating rouleaux formation. They were positively stained by periodic acid-Schiff stain. The histologic sections confirmed the cytologic diagnosis of Askin tumor. Four of the patients died within 7-11 months after treatment began.

[Infrequent clinical presentation of Askin's tumor]

Malign small cell tumors in the thoracopulmonary region is a tumor of neuroectodermic origins with polymorphous and infrequent presentation. It is mostly found among young people, developing an aggressive and severe course. It is a small cell tumor involving small quantities of cytoplasm without glucogen, round or oval nucleus with disperse chromatin, and little prominent nucleolus without tendency of manifesting pseudo red spots, being PAS negative. Two cases which initially resembled pleuropulmonary infection are presented. Case 1: Sixteen year old male. Presented with a high fever, pleuritic thoracic pain, and a cough with little expectoration. He was diagnosed with severe pulmonary infection and parapneumonic right pleural discharge. His condition improved with antibiotic treatment, but the cough persisted. Thoracoabdominal echography showed right pleural discharge and possible hepatic mass. Surgical intervention was performed. Askin's tumor was detected by biopsy. He began treatment with chemotherapy. Case 2: Thirty-four year old woman. Presented with non-productive cough, pleuritic thoracic pain, and high fever. In the thoracic TAC, there was right pleural discharge along with images suggesting hypodense mass. Given the patient's lack of response to antibiotics, a thoracotomy was performed. The anatomopathological diagnosis was Atkin's tumor. After beginning treatment, the patient died after ten days.

Small cell osteosarcoma of bone: an immunohistochemical study with differential diagnostic considerations

Seventy-nine cases of small round cell tumors involving bone were studied in an attempt to learn whether the immunohistochemical features of the lesions might allow distinction of small cell osteosarcoma from other potential differential diagnostic considerations, including Ewing's sarcoma, atypical Ewing's sarcoma, primitive neuroectodermal tumor, mesenchymal chondrosarcoma, lymphoma, and the Askin tumor. The tissues studied were all formalin-fixed, decalcified, paraffin sections from patients between the ages of 16 and 48 years. With one exception (a small cell osteosarcoma), none of the lesions was cytokeratin positive. Moreover, none of the lesions was epithelial membrane antigen, desmin, factor VIII-related antigen, synaptophysin, or Leu-M1 positive. Accordingly, strong positivity for these antibodies in a majority of tumor cells should prompt inclusion of tumor types other than those listed above in the differential diagnosis. Vimentin positivity was seen in a majority of the tumors studied irrespective of histologic type. Scattered tumor cells (< 25%) showed positivity with antibodies to muscle-specific actin and smooth muscle actin in several of the different tumor types studied. No lesions other than lymphoma were leukocyte-common antigen (LCA) positive; all but two lymphomas were LCA positive, while all but one lymphoma were L26 positive. One (lymphoblastic) lymphoma was LCA and L26 negative. S-100, neuron-specific enolase, and Leu-7 did not prove to be specific for "neural-associated" tumors, but rather appeared in some small cell osteosarcomas, Ewing's sarcomas, atypical Ewing's sarcomas, primitive neuroectodermal tumors, mesenchymal chondrosarcomas, lymphomas, and Askin tumors. Antibody to cell surface antigen HBA71 was positive in three Ewing's sarcomas (two typical and one atypical) and negative in small cell osteosarcoma (three cases), mesenchymal chondrosarcoma (two cases), and lymphoma (one case). While some guidance may be derived from analysis of immunohistochemical staining patterns in a given lesion, the results reported in the present study do not suggest that routine immunohistochemistry alone will permit distinction of these small cell tumors of bone from one another. The value of immunohistochemical studies appears to lie particularly in the use of antibodies to LCA and S-100 protein to distinguish lymphoma and mesenchymal chondrosarcoma, and perhaps antibody to HBA71 to distinguish neural family lesions (such as Ewing's sarcoma), from other small cell tumors, such as small cell osteosarcoma.