Small cell osteosarcoma. A clinicopathologic study of 27 cases

Small cell osteosarcoma versus fusion-driven round cell sarcomas of bone: retrospective clinical, radiological, pathological, and (epi)genetic comparison with clinical implications

Small cell osteosarcoma (SCOS), a variant of conventional high-grade osteosarcoma (COS), may mimic fusion-driven round cell sarcomas (FDRCS) by overlapping clinico-radiological and histomorphological/immunohistochemical characteristics, hampering accurate diagnosis and consequently proper therapy. We retrospectively analyzed decalcified formalin-fixed paraffin-embedded (FFPE) samples of 18 bone tumors primarily diagnosed as SCOS by methylation profiling, fusion gene analysis, and immunohistochemistry.In eight cases, the diagnosis of SCOS was maintained, and in 10 cases it was changed into FDRCS, including three Ewing sarcomas (EWSR1::FLI1 in two cases and no identified fusion gene in the third case), two sarcomas with BCOR alterations (KMT2D::BCOR, CCNB3::BCOR, respectively), three mesenchymal chondrosarcomas (HEY1::NCOA2 in two cases and one case with insufficient RNA quality), and two sclerosing epithelioid fibrosarcomas (FUS::CREBL3 and EWSR1 rearrangement, respectively).Histologically, SCOS usually possessed more pleomorphic cells in contrast to the FDRCS showing mainly monomorphic cellular features. However, osteoid was seen in the latter tumors as well, often associated with slight pleomorphism. Also, the immunohistochemical profile (CD99, SATB2, and BCOR) overlapped.Clinically and radiologically, similarities between SCOS and FDRCS were observed, with by imaging only minimal presence or lack of (mineralized) osteoid in most of the SCOSs.In conclusion, discrimination of SCOS, epigenetically related to COS, versus FDRCS of bone can be challenging but is important due to different biology and therefore therapeutic strategies. Methylation profiling is a reliable and robust diagnostic test especially on decalcified FFPE material. Subsequent fusion gene analysis and/or use of specific immunohistochemical surrogate markers can be used to substantiate the diagnosis.

Pediatric Osteosarcoma: Pearls and Pitfalls

Osteosarcoma is a malignant bone tumor most commonly presenting in children. It has a bimodal distribution with a peak incidence occurring during the ages of 10-14 years old and in adults greater than age 65. The first peak of osteosarcoma correlates with the increased proliferation of bone during the pubertal growth period. Osteosarcoma most frequently presents with localized bone pain, swelling, and an antalgic gait. The patient may attribute symptoms to trauma or strenuous exercise, causing the patient to be managed conservatively. In these cases, the pain persists and eventually leads to further evaluation. The most common type of osteosarcoma is the conventional high-grade osteosarcoma. For conventional osteosarcoma, the diagnosis is typically made or strongly suggested based upon the initial radiographic appearance. Other types of osteosarcomas include low grade central, telangiectatic, small-cell, surface and intracortical. Consequently, it is important for radiologists to be aware of these subtypes and the imaging features that differentiate them from other etiologies to prevent a delay in treatment.

Clarifying prognostic factors of small cell osteosarcoma: A pooled analysis of 20 cases and the literature

Introduction

Small cell osteosarcoma (SCOS) is a rare subtype of osteosarcoma, with limited studies mainly focusing on histological features. Our study aims to analyze our own patients and those reported in the literature to increase the recognition of this rare disease, to evaluate patient survival and to further determine potential prognostic factors.

Material and methods

Twenty patients with SCOS were treated in our hospital between 2010 and 2019. Their follow-up data were collected retrospectively. A total of 336 literature cases from 58 manuscripts were retrieved by means of a PubMed search with the key word “small cell osteosarcoma”. Data pertaining to treatment and follow-up were extracted. We performed a pooled analysis for the survival of patients and the risk factors for local recurrence (LR), as well as metastatic disease (MD), in a total of 160 patients using the Kaplan-Meier method and Cox regression method.

Results

We reported our experience in diagnosing and treating SCOS. In our cases, elevated alkaline phosphatase (P = 0.013) and lactate dehydrogenase (P = 0.001) significantly impaired overall survival. In the pooled analysis, SCOS was diagnosed at the median age of 17 years and affected both sexes almost equally. The median follow-up duration was 19.5 months. In the pooled analysis cases, the 5-year overall survival rate was 38.6%, and 36.4% of patients survived 10 years. However, an increasing trend was detected, indicating recent improvements in management. The surgical margin status (P = 0.024) and metastases (P = 0.008) significantly impaired overall survival, and the response to chemotherapy was related to disease-free survival (P = 0.012). LR and MD were significantly correlated (P = 0.002) and could be observed after 5 years of follow-up. LR was significantly dependent on response to chemotherapy (P = 0.020). The development of MD seemed to be affected by response to chemotherapy (P = 0.060). Correlations between imaging features and prognosis were not detected.

Conclusions

This study suggested that positive margins, poor response to chemotherapy and MD are negative prognostic factors for SCOS, implied the potential role of laboratory examinations in the survival prediction and supported the need for prolonged or more intensive surveillance in patients with MD or LR. More well-documented literatures are encouraged to allow further confirmations.

[Extraskeletal osteosarcoma: nosologocal diversity, morphology, differential diagnosis, and features of metastasis]

Extraskeletal osteosarcoma is a rare malignant tumor with histologic similarities to primary bone osteosarcoma. However, there are distinct differences in epidemiology, imaging features, biological characteristics, prognosis, and management compared with osteogenic osteosarcoma. Extraskeletal osteosarcoma is usually characterized as high-grade neoplasm with clinically aggressive behavior, poor prognosis, frequent recurrence/lymphogenic metastatsis, and resistence to chemotherapy. A noteworthy feature of extraskeletal osteosarcoma is the fact that almost all existing biological phenomena described in mesenchymal oncopathology (except primary-multiple lesions) are present in this tumor, namely: secondary malignancy, association with syndromes, partial spontaneous regression of the tumor, dedifferentiation, bone invasion, biphasic pathology. In this paper, we have discussed in detail the tumor morphology, histological subtypes, prognostic factors and differential diagnosis.

Establishment and Characterization of a Human Small Cell Osteosarcoma Cancer Stem Cell Line: A New Possible In Vitro Model for Discovering Small Cell Osteosarcoma Biology

Osteosarcoma (OSA) is the most common primary malignant bone tumor, usually arising in the long bones of children and young adults. There are different subtypes of OSA, among which we find the conventional OS (also called medullary or central osteosarcoma) which has a high grade of malignancy and an incidence of 80%. There are different subtypes of high grade OS like chondroblastic, fibroblastic, osteoblastic, telangiectatic, and the small cell osteosarcoma (SCO). In this study, for the first time, we have isolated, established, and characterized a cell line of cancer stem cells (CSCs) from a human SCO. First of all, we have established a primary finite cell line of SCO, from which we have isolated the CSCs by the sphere formation assay. We have proved their in vitro mesenchymal and embryonic stem phenotype. Additionally, we have showed their neoplastic phenotype, since the original tumor bulk is a high grade osteosarcoma. This research demonstrates the existence of CSCs also in human primary SCO and highlights the establishment of this particular stabilized cancer stem cell line. This will represent a first step into the study of the biology of these cells to discover new molecular targets molecules for new incisive therapeutic strategies against this highly aggressive OSA.

Primary Rhabdomyosarcoma Mimicking a Small Cell Sarcoma of Bone: A Nude Mice Xenograft, Cytogenetic, and Molecular Approach

Small cell sarcomas of bone are difficult to classify and diagnose. The present case deals with such a tumor in which the original biopsy and the resected specimen, studied by histology before chemotherapy, provided no final information about its real nature. Thus several techniques were applied to discern its histogenesis and biology. Myogenin proved positive in isolated cells of the primary neoplasm but was extensively expressed in nude mice xenografts. Electron microscopy confirmed the existence of myofilaments. The cytogenetic analysis revealed a large number of chromo somal abnormalities, but not those found in the Ewing's/PNET (peripheral neuroectodermal tumor) family of tumors. This was confirmed by polymerase chain reaction (RT-PCR) wherein no EWS/Fli 1 or PAX3/FKHR gene rearrangements were detected. Based upon these studies, a rhabdomyosarcoma of bone was diagnosed. Clinically the neoplasm showed a highly aggressive behavior, causing death of the patient within 2 years after diagnosis.

Small cell osteosarcoma of the parietal region: a unique case at an unusual site

Small cell osteosarcoma is a rare tumour that histologically mimics Ewing sarcoma, mesenchymal chondrosarcoma and lymphoma, the presence of osteoid being diagnostic. This variant needs different management protocol, being non-radiosensitive and behaving more aggressively than conventional osteosarcoma. The aim of this article is to highlight such an entity at an unusual site--the parietal region--with unique diagnostic, treatment and prognostic considerations in a 16-year-old girl.

Cytological diagnosis of small cell osteosarcoma of the bone

Small cell osteosarcoma (OS) is a rare histological variant of OS that poses unique diagnostic difficulties. We present a case of a 10-year-old child who underwent fine needle aspiration cytology (FNAC) from a mass in the right thigh. The cytological findings were those of a malignant small round cell tumor, closest to small cell OS. The FNAC findings were confirmed on histopathology.

Small cell extraskeletal osteosarcoma: a rare case report

Extraskeletal osteosarcoma is a rare malignant mesenchymal neoplasm and its small cell variant is one among the rarest variant. This article describes a 60-year-old woman presenting with a large, lobulated, painful mass in left thigh with associated history of trauma since 18 months. Her magnetic resonance imaging showed a variegated mixed intensity lesion with associated cystic degeneration, necrosis and matrix arborizing nearby muscles. Fine needle aspiration cytology showed a small cell lesion with very scant osteoid. Tumor was excised and histopathological diagnosis was small cell osteosarcoma involving adjacent muscles and fat with sparing of lymph nodes. The aim of this article is to present the clinical, radiological, cyto-histological and immunohistochemical features of this extremely rare lesion.

Endovascular Treatment of Vertebral Column Metastases Using Intra-Arterial Cisplatin: Pilot Experience

Background and Importance. Treatment of spinal column metastatic tumors is challenging, especially in the setting of progressive disease despite previous radiation and chemotherapy. Intra-arterial chemotherapy is an uncommonly used but established treatment for head and neck cancers, retinoblastoma, and glioblastoma. The author reports extension of the IAC concept to vertebral metastatic tumors. Clinical Presentation. Two patients with intractable spinal pain secondary to spinal metastatic involvement at T11-L1 segments were treated with intra-arterial injections of cisplatin, with simultaneous sodium thiosulfate chelation. The first patient, a 60-year old female with metastatic lung carcinoma underwent, three cycles of therapy over a 9-week period; the treated regions demonstrated bone remodeling and sclerosis. The second case was a 40-year old male with malignant pheochromocytoma, who underwent a single treatment and succumbed 5 weeks later from progressive widespread disease. Both patients reported significant pain relief and neither of them exhibited a decline in neurologic function. Conclusion. The intra-arterial delivery of cisplatin appeared to be well tolerated in the two cases. In the case with the longest survival, the treated vertebral segments became more sclerotic, consistent with biomechanical stabilization. Endovascular treatment of spinal metastases may hold promise, especially as newer categories of biologic agents become more widely available.

Contralateral referred pain in a patient with intramedullary spinal cord metastasis from extraskeletal small cell osteosarcoma

CONTEXT

Referred pain has been observed in some patients after cordotomy, wherein noxious stimulus applied to a region rendered analgesic by cordotomy produces pain at a spot different from the one where the noxious stimulus is applied. We report a patient who had intramedullary spinal cord metastasis of extraskeletal small cell osteosarcoma, a rare form of metastatic disease, and experienced contralateral referred pain.

FINDINGS

Initially, the patient had a mass in the left posterior neck region and later developed a large extradural mass at the C3-C7 level. The masses were excised, and the histological findings led to a diagnosis of small cell osteosarcoma. He underwent chemotherapy and radiation therapy. He experienced numbness in his left leg; subsequently, the numbness slowly spread up the thigh to the left side of the abdomen. When pinched in the numb area on the left side of the body, he felt as though he had been pinched in both that area and the corresponding area on the right side. A magnetic resonance imaging scan showed an enhancing lesion in the right side of the cord at the C6-C7 level.

CONCLUSION/CLINICAL RELEVANCE

An intramedullary spinal cord metastasis can arise from primary extraskeletal small cell osteosarcoma and cause contralateral referred pain, especially in a mirror-image location. Contralateral referred pain may be caused by a subsidiary pathway comprising ascending chains of short neurons that link the dorsal horn neurons longitudinally and latitudinally.

Small cell osteosarcoma of the mandible: Case report and review of its diagnostic aspects

Small cell osteosarcoma, a rare histological subtype, has very infrequently been reported in the mandible. We present a case of a 28-year-old female who had classic signs, symptoms, and radiographic features of the lesion. The histology showed sheets of small round cells and osteoid. The absence of the latter would have made it difficult to distinguish from other small round cell tumors of bone, especially Ewing's sarcoma. We have reviewed the clinical and radiographic features, cytologic and histologic characteristics, as well as the immunohistochemistry and molecular genetics of small cell osteosarcoma.

Small Round Cell Tumors of Bone

Diagnosing small round cell tumors (SCRTs) can be a difficult task for pathologists due to overlapping clinicopathologic features. This review highlights the clinical, radiographic, histologic, immunohistochemical, and genetic features of the most common SRCTs involving bone with an emphasis on differential diagnosis. SRCTs are a heterogeneous group of neoplasms characterized by poorly differentiated cells with small, blue, round nuclei and scant cytoplasm. They can occur as primary tumors in bone or soft tissue.

Osteosarcoma: Differential Diagnostic Considerations

Accurate diagnosis of bone-forming tumors, including correct subclassification of osteogenic sarcoma is critical for determination of appropriate clinical management and prediction of patient outcome. The morphologic spectrum of osteogenic sarcoma is extensive, however, and its histologic mimics are numerous. This review focuses on the major differential diagnoses of the specific subtypes of osteosarcoma, presents summaries of various diagnoses, and provides tips to overcoming pitfalls in diagnosis.

Small cell osteosarcoma: cytopathologic characteristics and differential diagnosis

Small cell osteosarcoma may present a challenging primary diagnosis on cytologic assessment owing to its rarity and its morphologic similarity to other small round blue cell tumors. Five cases of small cell osteosarcoma from our cytopathology archives were identified and reviewed and cytologic features elaborated. Three cases were fine-needle aspirations from bony lesions in the classic location for osteosarcoma (2 distal femur and 1 proximal tibia), and 2 aspirations were from metastases. Common cytomorphologic features included relatively small to intermediate cell size, high nuclear/cytoplasmic ratios, round nuclei, minimal anisonucleosis, finely granular nuclear chromatin, fine cytoplasmic vacuoles, and only rare osteoid. Small cell osteosarcoma shares many of the well-described cytomorphologic features of classic osteosarcoma, but the relatively small cells, round hyperchromatic nuclei, and scant osteoid constitute the common denominator. Correlation with radiographic findings and ancillary tests can aid in definitive diagnosis.

Small cell tumors of bone

Bone tumors are fortunately rare, but small cell tumors of bone are a relatively common subset of these lesions. They comprise of a diverse group of primary and metastatic neoplasms in both children and adults. The most common small cell tumors of bone include Ewing sarcoma/primitive neuroectodermal tumor, small cell osteosarcoma, multiple myeloma, lymphoma, leukemia, neuroblastoma, rhabdomyosarcoma, and Langerhans cell histiocytosis. Although each entity has its distinctive features, the differential diagnosis of this group of tumors is still challenging because they are all "small, blue, and round cell tumors", histologically. The correct diagnosis of small cell tumors of bone depends on an evaluation of clinical, radiologic, pathologic, and genetic features. Patients' age and sex are very important, as are the signs and symptoms at presentation. Radiologically, which bone is involved, the specific portion of the bone (epiphysis, metaphysis, or diaphysis; cortex vs. medulla) involved, and the radiographic manifestations (lytic, blastic, or mixed lytic and blastic) are also often critical parameters for the diagnosis. In recent years, with a better understanding of the molecular and cytogenetic background of several small cell tumors, more accurate diagnoses have been supported by the clinicopathologic criteria and by a panel of immunohistochemical studies. In this review we will provide an overview of the clinical, radiologic, pathologic, and genetic characteristics of these tumors.

18F-FDG PET/CT as an indicator of progression-free and overall survival in osteosarcoma

The aim of our study was to retrospectively evaluate whether maximum standardized uptake value (SUV(max)), total lesion glycolysis (TLG), or change therein using (18)F-FDG PET/CT performed before and after initial chemotherapy were indicators of patient outcome.

METHODS

Thirty-one consecutive patients who underwent (18)F-FDG PET/CT before and after chemotherapy, followed by tumor resection, were retrospectively reviewed. Univariate Cox regression was used to analyze for relationships between covariates of interest (SUV(max) before and after chemotherapy, change in SUV(max), TLG before and after chemotherapy, change in TLG, and tumor necrosis) and progression-free and overall survival. Logistic regression was used to evaluate tumor necrosis.

RESULTS

High SUV(max) before and after chemotherapy (P = 0.008 and P = 0.009, respectively) was associated with worse progression-free survival. The cut point for SUV(max) before chemotherapy was greater than 15 g/mL* (P = 0.015), and after chemotherapy it was greater than 5 g/mL* (P = 0.006), as measured at our institution and using lean body mass. Increase in TLG after chemotherapy was associated with worse progression-free survival (P = 0.016). High SUV(max) after chemotherapy was associated with poor overall survival (P = 0.035). The cut point was above the median of 3.3 g/mL* (P = 0.043). High TLG before chemotherapy was associated with poor overall survival (P = 0.021). Good overall and progression-free survival was associated with a tumor necrosis greater than 90% (P = 0.018 and 0.08, respectively). A tumor necrosis greater than 90% was most strongly associated with a decrease in SUV(max) (P = 0.015).

CONCLUSION

(18)F-FDG PET/CT can be used as a prognostic indicator for progression-free survival, overall survival, and tumor necrosis in osteosarcoma.

Pediatric and adult osteosarcoma: comparisons and contrasts in presentation and therapy

Most data on osteosarcoma is derived from pediatric studies. Although the majority of adult patients with osteosarcoma are young adults, who might be treated in a similar fashion, experience derived from a slightly older population is helpful in directing therapy. We treated a series of 123 patients with osteosarcoma of the extremities with adriamycin and cisplatin as induction therapy. Adriamycin was infused intravenously at 90 mg/m2 over 96 h. Cisplatin was infused intra-arterially at 120-160 mg/m2 over 2-24 h. Sequential addition of methotrexate and methotrexate plus ifosfamide in subsequent cohorts improved the continuous relapse-free survival of poor responders such that overall survival improvement was noted in the group where therapy was modified by adding both agents to those with <90% tumor necrosis. Patients with chondroblastic osteosarcoma with poor necrosis had a trend towards improved continuous relapse-free survival compared with other patients with conventional osteosarcoma. Histologic variants of osteosarcoma except telangiectatic osteosarcoma had a worse prognosis than those with conventional osteosarcoma. The variants, especially dedifferentiated parosteal osteosarcoma and dedifferentiated well-differentiated intraosseous osteosarcoma are more common in adults than children, accounting for some of the inferior prognosis in adults. Older patients obviously cannot tolerate the doses of therapy given to children and young adults, again decreasing the chances of successful treatment. Patients with secondary osteosarcoma are often much older as are many with osteosarcomas of the pelvis and jaw. These tumors tend to be less responsive. An attempt to intensify therapy in poor-prognosis patients with a three-drug regimen of adriamycin, cisplatin, and ifosfamide with peripheral stem cell support was unsuccessful at prolonging relapse-free survival, and we no longer use that approach.

Radiological appearances of appendicular osteosarcoma: a comprehensive pictorial review

Osteosarcoma is the most common primary malignant tumour of bone in adolescents and young adults. Hence, a comprehensive knowledge of the common and unusual imaging appearance of this tumour is essential. Correct diagnosis of the various varieties of osteosarcoma is important for optimal clinical management including staging, biopsy, treatment and follow-up of patients. This review article provides a comprehensive approach to the radiological diagnosis of the different types of appendicular osteosarcoma and illustrates the role of CT and MRI in further characterisation.

Small Round Cell Tumors of Bone

Context.—Primary small round cell tumors of the bone are a heterogeneous group of malignant neoplasms presenting predominantly in children and adolescents. They include Ewing sarcoma/peripheral neuroectodermal tumor or Ewing family tumors, lymphoma, mesenchymal chondrosarcoma, and small cell osteosarcoma. Even though they share many morphological similarities, their unique biological and genetic characteristics have provided substantial insights into the pathology of these diverse neoplasms.

Objective.—To provide an overview of the clinical, radiologic, pathologic, and genetic characteristics of these tumors along with a pertinent review of the literature.

Data Sources.—A literature search using PubMed and Ovid MEDLINE was performed, and data were obtained from various articles pertaining to clinicopathologic, biological, and genetic findings in these tumors. Additionally, findings from rare cases have been included from author's subspecialty experience.

Conclusion.—The diagnosis of small round cell tumors can be made accurately by applying clinicopathologic criteria, as well as a panel of immunohistochemical and genetic studies in appropriate cases. Molecular genetic studies may provide further insight into the biology, histogenesis, and prognosis of these tumors.

Tomografia computadorizada na análise dos padrões de calcificações nos tumores ósseos da bacia em pediatria: nova abordagem

OBJETIVO: No grupo pediátrico, o diagnóstico radiológico dos tumores dos ossos ilíacos, ísquios e púbis apresenta dificuldades e peculiaridades próprias, mas a literatura revisada não trata especificamente desse tema. Este trabalho pretende investigar a existência de padrões radiológicos confiáveis para o diagnóstico diferencial desses tumores. MATERIAIS E MÉTODOS: Foram revistos os achados radiológicos de tumores dos ossos do quadril em dez pacientes com idades entre 8 e 19 anos. RESULTADOS: Reação óssea (esclerose ou lise), reação periosteal (lamelar em camada única, múltiplas camadas ou radial), extensão do tumor no osso e grau de invasão das partes moles revelaram baixa especificidade. As calcificações nas partes moles, consideradas em conjunto, foram inespecíficas. Contudo, separando as próximas do osso comprometido, que apresentam formas e tamanhos variados - padrão I -, daquelas afastadas do osso, finas e amorfas - padrão II -, observamos que o padrão I foi totalmente inespecífico e o padrão II foi identificado nos três casos de osteossarcoma (100%) e em apenas um dos casos de Ewing (16,6%). CONCLUSÃO: Neste material, as calcificações padrão II revelaram sensibilidade de 100% e especificidade de 90% para osteossarcoma. Contudo, sua importância pode não se limitar ao diagnóstico radiológico. As calcificações padrão II indicam, provavelmente, os sítios ideais para biópsia.

Case reports: Osteosarcoma without radiographic evidence of tumor

There have been cases of osteosarcoma in which conventional radiographs showed only minimal abnormalities. However, the absence of any evidence of tumor has not been reported. We report a unique case of osteosarcoma in a patient who originally presented with a fracture incurred after minimal trauma. The patient had no radiographic evidence of the tumor even after retrospective analysis.

The spectrum of pediatric tumors in infancy, childhood, and adolescence: a comprehensive review with emphasis on special techniques in diagnosis

The spectrum of pediatric tumors varies considerably, from those derived from blastemal cells in various organ systems to proliferations of soft tissue supporting cells to hamartomatous processes that mimic malignant tumors. Small round cell tumors are often undifferentiated or poorly differentiated, making it difficult sometimes to provide a definitive diagnosis. Both benign and malignant tumors require a coordinated method for diagnosis, and need a comprehensive evaluation to provide the most appropriate diagnosis for designing therapy and predicting prognosis. Pediatric tumors require the integration of routine histopathologic examination with histochemical, immunocytochemical, ultrastructural, cytogenetic, and diagnostic molecular pathology techniques. This review provides updated guidelines with respect to the application of these special techniques in this rapidly evolving diagnostic arena.

Current treatment of osteosarcoma

A comprehensive multidisciplinary approach has transformed osteosarcoma from a disease with a modest long-term survival to one in which at least two-thirds of patients will be cured. Surgery remains the vital modality for treating the primary tumor, whereas adjuvant chemotherapy plays an essential role in the control of subclinical metastatic disease. Complete surgical excision of the primary tumor remains an essential element of treatment. For many patients, a combination of advances in surgical technique, improved imaging modalities to accurately document tumor extent, and the effect of neoadjuvant chemotherapy has made limb salvage procedures a safe alternative to amputation. In some patients for whom complete surgical excision is impossible, the addition of radiation therapy may allow local tumor control. The most effective chemotherapy agents currently in use include high-dose methotrexate, doxorubicin, cisplatin, and ifosfamide/etoposide. The optimal schedule of therapy is still being investigated, as is the role of dose intensification. Unfortunately, some groups of patients remain at high risk of eventual relapse. Those whose tumors show relatively low degrees of necrosis after administration of chemotherapy have poorer survival than patients with more chemotherapy-responsive tumors. Similarly, patients who present with overt metastatic disease (particularly bone metastases), as well as patients with tumors that recur after treatment, continue to have an unsatisfactory outcome. These groups, in particular, may benefit from future investigations into novel agents, such as biological response modifiers, antiangiogenesis factors, and growth receptor modulation.

Small cell osteosarcoma of the ulna: a case report and review of the literature

We report a case of small cell osteosarcoma arising in the distal ulna. The radiologic and pathologic features of this histologic variant of osteosarcoma that allow differentiation from other lytic lesions with small round cells are discussed.

Small cell osteogenic sarcoma of the ribs: cytological, immunohistochemical, and ultrastructural study with literature review

Small cell osteosarcoma (OS) is a rare variant of OS that is composed of small cells resembling those of Ewing's sarcoma (ES) with recognizable osteoid. This type of tumor often creates difficulty in making a diagnosis when tissue samples do not include osteoid. The frequent sites are long bones and until now there have been no reported cases arising in the ribs. A case is reported here of small cell OS occurring in the ribs of a 37-year-old female with its aspiration cytologic and electron microscopic characteristics. In the cytologic smear, the small round neoplastic cells were individually scattered or arranged in small nests. The nuclei were hyperchromatic and oval with no visible nucleoli. Ultrastructurally, the nuclei had a round or oval euchromatic chromatin pattern and occasional nucleoli. The scanty cytoplasm contained a small quantity of organelles including either tubular or dilated cisternae of RER, a few mitochondria, and free or polyribosomes. Other organelles were absent. Although the electron microscope sample of this case did not include bone mineral (hydroxy apatite), the electron microscopic features of the tumor cells were unique and useful for exclusion of other small round cell neoplasms.

Small cell osteosarcoma of bone. Review of 72 cases

BACKGROUND

Small cell osteosarcoma of bone is a rare form of osteosarcoma, with an incidence rate of 1.3%. This tumor must be differentiated from other small cell malignancies because of treatment considerations, particularly patient response to chemotherapy.

METHODS

Clinicopathologic findings in 72 cases (22 from Mayo Clinic files and 50 from consultation files) of small cell osteosarcoma of bone were studied.

RESULTS

The femur was the most common bone involved, although the tumor was found in all portions of the skeleton. Radiographic features (available in 35 cases) suggested a diagnosis of osteosarcoma in 20 cases, Ewing's sarcoma or lymphoma in 14 cases, and giant cell tumor in 1 case. Histologically, there were four types according to the predominant cell size and cytologic features. Osteoid production was identified in all tumors. Complete treatment and follow-up data were available for 45 cases. Generally, in those cases without surgical treatment, greater than 60% of patients died of disease within 2 years. If the surgical procedure was associated with a marginal tumor margin, the prognosis was poor. In the 30 patients with wide or radical surgical margins, at last follow-up 13 were alive with no evidence of disease, 2 were alive with disease, and 15 died of disease at 5 months to 13.1 years after diagnosis. In 16 of 22 Mayo Clinic patients, excluding those who presented with metastasis, the cumulative 5-year survival rate was 28.9%. Median survival time in patients who had surgery with additional chemotherapy was 13.4 years, compared with 1.4 years in patients who underwent surgery alone (P = 0.17).

CONCLUSIONS

Small cell osteosarcoma is a definite reproducible histologic entity. Treatment should be based on a protocol for osteosarcoma.

Small cell osteosarcoma of the soft tissue

The lesion we described is an osteoid producing mitotically active spindle cell soft tissue neoplasm, which has light and ultrastructural features of an osteosarcoma. By immunohistochemistry it marks with p30/32MIC2-directed antibodies but fails to react with antibodies associated with other soft tissue neoplasms. The precise histogenesis of the lesion is unknown, but failure to elicit a periosteal reaction makes the periosteum less likely to be the primary tissue of origin. The failure to demonstrate any radiologic or histologic evidence of involvement of the underlying bone leaves the soft tissue as the most reasonable site of origin, although the parosteal region cannot be completely excluded.

Electron microscopy in the diagnosis of small round cell tumors of bone

Small round cell tumors involving bone can present problems in differential diagnosis by light microscopy. In exploring the role of electron microscopy in this situation, seven small cell osteosarcomas and seven mesenchymal chondrosarcomas were examined by electron microscopy and compared with typical and atypical Ewing's sarcomas. There is much overlap in the ultrastructural features of these tumors, but electron microscopy is helpful to establish or confirm a diagnosis of typical Ewing's sarcoma and, if representative matrix is present, of small cell osteosarcoma.

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.

Cytogenetics and molecular biology of small round-cell tumors and related neoplasms. Current status

Recent years have witnessed considerable advances in cytogenetics and molecular biology of small round-cell tumors. These advances are summarized and discussed in this article.

The ultrastructure of small-cell osteosarcoma, with a review of the light microscopy and differential diagnosis

Small-cell osteosarcoma is a rare form of osteosarcoma and often poses difficulty in differential diagnosis when tissue samples do not include any diagnostic osteoid. By light microscopy, it may be difficult to distinguish small-cell osteosarcoma from other small-cell neoplasms, especially Ewing's sarcoma and mesenchymal chondrosarcoma. Relatively little has been reported about the ultrastructural characteristics of small-cell osteosarcoma, whereas electron microscopic examination has proven very useful in the diagnosis of most other small-cell neoplasms. We have studied four proven small-cell osteosarcomas in detail at the electron microscopic level and found their common features to be a high nucleocytoplasmic ratio, poorly differentiated cytoplasm, numerous free ribosomes and mitochondria as the next most prevalent organelle, small junctions, and envelopment of individual and groups of cells by matrix. Beyond these characteristics, cytoplasmic organelles and nuclear features varied, and no single pathognomonic ultrastructural picture was observed. However, within the range of possible ultrastructure of small-cell osteosarcoma, most small-cell neoplasms can be ruled out. Only certain examples of Ewing's sarcoma and mesenchymal chondrosarcoma may be indistinguishable from it when osteoid is not present in the sample.