Chordomas of the mediastinum: clinicopathologic, immunohistochemical, and ultrastructural study of six cases presenting as posterior mediastinal masses

Unusual Presentation of Thoracic Chordoma with Spinal Epidural Hematoma: A Rare Case Report and PRISMA-Driven Systematic Review

A chordoma is a slow growing, locally invasive, low-grade tumor belonging to the sarcoma family. It mainly affects the sacrum and skull base. We present a case of thoracic chordoma initially presented with epidural hematoma (EDH), which is a rare clinical entity. We reported this case, and also performed a PRISMA-driven systematic review to summary the similar cases in the literature. This review includes the clinical characteristics and outcome of thoracic chordoma. Our case involves a 60-year-old male who, despite no history of trauma, presented with acute paraparesis. An epidural hematoma was identified at T6 level, leading to a surgical intervention involving T4-6 laminectomy and fixation. Six months subsequent to surgery, the patient experienced progressive lower limb weakness and spasticity. Computed tomography (CT) exhibited erosion of T6 and an associated aggressive mass. Magnetic resonance imaging (MRI) revealed a large heterogenous soft tissue mass arising from the vertebral body and right pedicle of D6, protruding in the epidural space and compressing the spinal cord focally at this level. The mass measured approximately 5 × 4 × 3.5 cm. Magnetic resonance myelography indicated a filling defect at T5-6 level, confirming the intraspinal location of the soft tissue lesion. Complete excision of the mass confirmed the diagnosis of thoracic chordoma. Postoperative follow-up demonstrated notable improvement in the lower limb spasticity and paraparesis, and the patient started adjuvant radiotherapy. This case underscores the importance of maintaining a high index of suspicion when evaluating presentations resembling EDH.

De novo Versus Secondary Dedifferentiated Chordomas: A Population-Based Analysis and Integrated Individual Participant Data Meta-Analysis

OBJECTIVE

There is a lack of data about the clinicopathological and molecular characteristics of de novo versus secondary dedifferentiated chordoma (DC). This integrated study aimed to investigate the similarities and differences in clinicopathological manifestations, prognoses, and molecular profiles of these 2 subtypes.

METHODS

We accessed the Surveillance, Epidemiology, and End Results (SEER) Program for DC cases from 1975 to 2020. Three electronic databases were also searched for additional DCs. Individual patient data of DC patients from SEER and published literature were combined in integrated analyses.

RESULTS

After excluding duplicated patients, we identified 14 and 116 DC patients from SEER and published literature, respectively. There were 74 de novo, 39 secondary, and 18 cases with unknown origin. Our results showed that de novo and secondary DCs were not statistically different in terms of age, gender, primary location, tumor size, distant metastasis at diagnosis, extent of resection, and chemotherapy receipt. There was limited available molecular data for de novo and secondary DCs, though examples TP53 mutations were found in both. In addition, the rates of tumor relapse, metastasis during follow-up, and patient mortality were also comparable between the 2 groups. In the multivariate Cox regression model, we demonstrated that gross total removal and radiotherapy use were associated with prolonged survival of DCs.

CONCLUSIONS

De novo and secondary DCs were statistically comparable in terms of patient demographics, clinical manifestations, and prognoses. Gross total excision and radiotherapy were optimal treatments associated with better outcomes of DC patients.

Mesenchymal Tumors of the Mediastinum: An Update on Diagnostic Approach

Mesenchymal tumors of the mediastinum are a heterogenous group of rare tumors with divergent lineages. Mediastinal mesenchymal tumors are diagnostically challenging due to their diversity and morphologic overlap with nonmesenchymal lesions arising in the mediastinum. Accurate histologic diagnosis is critical for appropriate patient management and prognostication. Many mediastinal mesenchymal tumors affect distinct age groups or occur at specific mediastinal compartments. Neurogenic tumors, liposarcoma, solitary fibrous tumor, and synovial sarcoma are common mesenchymal tumors in the mediastinum. Herein, we provide an update on the diagnostic approach to mediastinal mesenchymal tumors and a review of the histologic features and differential diagnosis of common benign and malignant mesenchymal tumors of the mediastinum.

Dedifferentiated Chordoma: Clinicopathologic and Molecular Characteristics With Integrative Analysis

Dedifferentiated chordoma is a rare chordoma subtype characterized by a high-grade sarcoma juxtaposed to conventional chordoma. We identified a series of dedifferentiated chordomas, reviewed clinicopathologic features, performed next-generation sequencing in select cases, and analyzed all related English-language publications. Our series included 7 men and 3 women (age 15 to 80 y [median: 54 y]; <1% of >1000 chordomas surveyed). The tumor (2.8 to 24.5 cm [median: 5.8 cm] in size) presented de novo or as recurrence (including postradiotherapy) in sacrum (n=5), skull base (n=2), lumbar spine (n=1), thoracic/mediastinum (n=1), and lung (n=1; as metastasis). Histologically, the dedifferentiated component (3% to 95% [median: 60%]) was pleomorphic-to-fibrosarcomatous, juxtaposed to conventional (n=8) or chondroid (n=2) component. By immunohistochemistry, the conventional/chondroid component consistently expressed cytokeratin and brachyury, whereas the dedifferentiated component showed loss of both. We identified a sacral conventional chordoma with INI1 loss, with one of the lung metastases showing biphasic histology with loss of cytokeratin and brachyury in the dedifferentiated component. Sequencing identified tumor suppressor mutations in 4 tumors, including TP53 mutations in the dedifferentiated component in 3 tumors. Of 7 patients with follow-up, 6 developed metastases; 4 died at 15 to 99 months (median: 24 mo) after dedifferentiated chordoma diagnosis. Collectively, of 87 dedifferentiated chordoma patients described in 1913-2020 (including 10 herein), the median overall survival was 20 months. In summary, dedifferentiated chordoma involves diverse sites and presents de novo, postradiotherapy, or as recurrence/metastasis months-to-years after initial diagnosis. The dedifferentiated component shows loss of brachyury and cytokeratin staining and harbors recurrent TP53 mutations, implicating tumor suppressor dysregulation in chordoma dedifferentiation.

Histochemical and immunohistochemical characterization of chordoma in ferrets

Chordomas of the tip of the tail in 6 ferrets were examined using histopathological, histochemical and immunohistochemical procedures. Histopathologically, round neoplastic cells containing numerous cytoplasmic vacuoles of varying sizes, categorized as “physaliphorous cells”, were observed in the amorphous eosinophilic or pale basophilic myxoid stroma. Physaliphorous cells were arranged in lobules and in a “chordoid” or “cobblestone” manner. The neoplasms were diagnosed as benign chordoma without local invasion and metastasis. Histochemically, the cytoplasm of small neoplastic cells was positive for periodic acid-Schiff stain and alcian blue (AB) pH 2.5 and pH 1.0 stains, but negative for hyaluronidase digestion-AB pH 2.5 stain. All neoplastic cells were strongly stained with colloidal ion, negative for high iron diamine AB pH 2.5 and toluidine blue pH 2.5 stains, and positive for Mayer’s mucicarmine stain. Immunohistochemistry using antibodies directed against low-molecular-weight cytokeratins (CK18, CK19 and CK20), vimentin and mucin core protein (MUC5AC) revealed that neoplastic cells had both epithelial and mesenchymal elements. The expression of low-molecular-weight cytokeratins suggests that neoplastic cells acquired the properties of glandular epithelial cells and produced epithelial mucus. Furthermore, the expression of cytokeratins, vimentin, S100 protein, brachyury and epithelial membrane antigen indicates that the neoplasms were equivalent to the classic type of human chordoma. Therefore, immunohistochemistry using these antibodies can be useful for the characterization of ferret chordoma.

Microcystic variant malignant mesothelioma presenting as a localized paraspinal mass

A 58-year-old man presented with productive cough and fever. Computed tomography (CT) scan of the chest showed an upper right paraspinal mass. CT-guided fine-needle aspiration biopsy showed lobules of vacuolated cells against a background of myxoid material. The cells demonstrated moderate to severe nuclear atypia and occasional mitoses. Immunohistochemistry revealed tumor cells to be immunoreactive for calretinin, WT-1, D2-40, cytokeratin (CK) 7, AE1/AE3, high molecular weight keratin, vimentin and epithelial membrane antigen, and negative for thyroid transcription factor-1, Ber-EP4, carcinoembryonic antigen, S100 protein, CK20, and CDX2. The combined morphologic and immunohistochemical findings confirmed the diagnosis of microcystic variant of localized malignant mesothelioma. The subsequent lung resection showed a pleural-based mass in the right upper lobe and confirmed the diagnosis. Awareness of the existence of unusual morphologic variants and localized forms of mesothelioma are necessary to avoid misdiagnosis of fine needle biopsy samples. Recognition of characteristic cytomorphologic features along with optimal use of panel of immunohistochemistry studies is crucial for making a specific diagnosis.

[Chordoma]

PURPOSES

To review in the literature, all the epidemiological, clinical, radiological, histological and therapeutic data regarding chordomas as well as various notochordal entities: ecchordosis physaliphora, intradural and intraparenchymatous chordomas, benign notochordal cell tumors, parachordomas and extra-axial chordomas. To identify different types of chordomas, including familial forms, associations with tuberous sclerosis, Ollier's disease and Maffucci's syndrome, forms with metastasis and seeding. To assess the recent data regarding molecular biology and progress in targeted therapy. To compare the different types of radiotherapy, especially protontherapy and their therapeutic effects. To review the largest series of chordomas in their different localizations (skull base, sacrum and mobile spine) from the literature.

MATERIALS

The series of 136 chordomas treated and followed up over 20 years (1972-2012) in the department of neurosurgery at Lariboisière hospital is reviewed. It includes: 58 chordomas of the skull base, 47 of the craniocervical junction, 23 of the cervical spine and 8 from the lombosacral region. Similarly, 31 chordomas in children (less than 18 years of age), observed in the departments of neurosurgery of les Enfants-Malades and Lariboisière hospitals, are presented. They were observed between 1976 and 2010 and were located intracranially (n=22 including 13 with cervical extension), 4 at the craniocervical junction level and 5 in the cervical spine.

METHODS

In the entire Lariboisière series and in the different groups of localization, different parameters were analyzed: the delay of diagnosis, of follow-up, of occurrence of metastasis, recurrence and death, the number of primary patients and patients referred to us after progression or recurrence and the number of deaths, recurrences and metastases. The influence of the quality of resection (total, subtotal and partial) on the prognosis is also presented. Kaplan-Meier actuarial curves of overall survival and disease free survival were performed in the entire series, including the different groups of localization based on the following 4 parameters: age, primary and secondary patients, quality of resection and protontherapy. In the pediatric series, a similar analysis was carried-out but was limited by the small number of patients in the subgroups.

RESULTS

In the Lariboisière series, the mean delay of diagnosis is 10 months and the mean follow-up is 80 months in each group. The delay before recurrence, metastasis and death is always better for the skull base chordomas and worse for those of the craniocervical junction, which have similar results to those of the cervical spine. Similar figures were observed as regards the number of deaths, metastases and recurrences. Quality of resection is the major factor of prognosis with 20.5 % of deaths and 28 % of recurrences after total resection as compared to 52.5 % and 47.5 % after subtotal resection. This is still more obvious in the group of skull base chordomas. Adding protontherapy to a total resection can still improve the results but there is no change after subtotal resection. The actuarial curve of overall survival shows a clear cut in the slope with some chordomas having a fast evolution towards recurrence and death in less than 4 years and others having a long survival of sometimes more than 20 years. Also, age has no influence on the prognosis. In primary patients, disease free survival is better than in secondary patients but not in overall survival. Protontherapy only improves the overall survival in the entire series and in the skull base group. Total resection improves both the overall and disease free survival in each group. Finally, the adjunct of protontherapy after total resection is clearly demonstrated. In the pediatric series, the median follow-up is 5.7 years. Overall survival and disease free survival are respectively 63 % and 54.3 %. Factors of prognosis are the histological type (atypical forms), localization (worse for the cervical spine and better for the clivus) and again it will depend on the quality of resection.

CONCLUSIONS

Many different pathologies derived from the notochord can be observed: some are remnants, some may be precursors of chordomas and some have similar features but are probably not genuine chordomas. To-day, immuno-histological studies should permit to differentiate them from real chordomas. Improving knowledge of molecular biology raises hopes for complementary treatments but to date the quality of surgical resection is still the main factor of prognosis. Complementary protontherapy seems useful, especially in skull base chordomas, which have better overall results than those of the craniocervical junction and of the cervical spine. However, we are still lacking an intrinsic marker of evolution to differentiate the slow growing chordomas with an indolent evolution from aggressive types leading rapidly to recurrence and death on which more aggressive treatments should be applied.

Lipomatous tumors of the anterior mediastinum with muscle differentiation: a clinicopathological and immunohistochemical study of three cases

Three cases of primary lipomatous tumors of the anterior mediastinum with prominent muscle differentiation are presented. The patients were two women and one man between the age of 52 and 68 years. All patients presented with progressive shortness of breath. Radiographically, all patients demonstrated anterior mediastinal tumors which were surgically resected. In two cases, the gross findings were those of circumscribed tumors, while one lesion was described as an ill-defined and unencapsulated neoplasm. Histologically, two cases corresponded to a well-differentiated liposarcoma, while the third was a thymolipoma. Extensive areas of smooth muscle were identified in one of the liposarcomas, while the other contained areas of mature skeletal muscle. The thymolipoma displayed a prominent myoid component. Immunohistochemical studies for muscle markers including smooth muscle actin, desmin, and myoglobin showed positive staining in the corresponding components. Follow-up information showed that one patient with liposarcoma died 60 months after initial diagnosis, while the other two patients remain alive and well 16 and 36 months after diagnosis, respectively. The current cases highlight the spectrum of muscle differentiation that can be seen in adipose tumors of the anterior mediastinum and also emphasize the difficulty that such a diagnosis can pose when confronted with limited mediastinoscopic biopsies.

A comparison of cell-cycle markers in skull base and sacral chordomas

OBJECTIVE

Despite refinement of surgical techniques and adjuvant radiotherapy, the prognosis for patients with a chordoma remains poor. Identification of prognostic factors related to tumor biology might improve this assessment and result in molecular markers for targeted therapy. Limited studies have been performed to unravel the impact of cell-cycle markers in chordoma, and those performed have shown inconclusive results. In the current study, we aimed to discover the impact of cyclin-dependent kinase 4 (CDK4) expression and its relation to prognosis and other cell-cycle markers in chordoma.

METHODS

Twenty-five human formalin-fixed, paraffin-embedded chordoma specimens were examined by immunohistochemistry for the expression of CDK4, protein 53 (p53), and murine double minute 2 (MDM2). The MIB-1 labeling index and mitotic index were used for the examination of proliferation. We collected detailed demographic and clinical data.

RESULTS

Overexpression of CDK4, p53, and MDM2 was found in five (20%), seven (28%), and 14 (56%) of the cases, respectively. All three cell-cycle markers showed a significant correlation with MIB1 labeling index. Expression of CDK4 (P = 0.02) and p53 (P < 0.01) were both significantly correlated with poor overall survival. Also, histologically observed necrosis (P < 0.05) and a dedifferentiated tumor subtype (P < 0.01) were related to adverse patient outcome.

CONCLUSION

Our results show that the expression of CDK4 and p53 are related to cell proliferation capacity and worse outcome in patients with chordoma.

A case of paravertebral mediastinal chordoma without bone destruction

We report a unique case of mediastinal paravertebral chordoma without bone destruction in a 47-year-old Japanese woman. She was admitted to hospital after a tumor was incidentally detected on a chest radiograph. The tumor was located in the paravertebral region of the mediastinum and did not show any destruction of the thoracic vertebra radiologically. The tumor was clinically diagnosed as a benign neurogenic tumor and the tumor was easily removed surgically. Microscopically, the tumor mainly consisted of tumor cells with extensively vacuolated cytoplasm, arranged in cord- and nest-like fashion against a myxoid matrix background. Immunohistochemically, the tumor cells showed diffuse positivity for pancytokeratin (AE1/AE3) and vimentin. The tumor cell nuclei were positive for brachyury, which is a key transcription factor of notochordal development. These results confirmed the tumor to be an extraosseous chordoma in the paravertebral mediastinal region, which is an extremely rare location for a chordoma.

The biological basis for modern treatment of chordoma

Chordomas are rare malignant tumors arising in bone of the spheno-occiput, sacrum, and vertebral column which can cause neurological deficit. Current management of chordoma involves safe resection followed by radiation therapy. However, surgical resection is often subtotal and chordoma often recurs despite optimal therapy. Despite years of effort, effective adjuvant therapy for denovo, recurrent and metastatic chordoma are absent and 5-year survival is at best 65%. While no chemotherapeutic agent has been demonstrated to be effective against chordoma in vivo, a greater understanding of the genetics and molecular biology of chordoma is opening up avenues of investigation towards the rational development of targeted therapies. Although enthusiasm for the use of already established or new investigational agents will increase with greater understanding of chordoma biology, laboratory studies of these agents are important prior to incorporation into clinical human trials. The authors review the current state of knowledge regarding chordoma and offer insight into potential new therapies for this rare and challenging tumor.

Specificity of brachyury in the distinction of chordoma from clear cell renal cell carcinoma and germ cell tumors: a study of 305 cases

Brachyury is recognized as a specific marker for notochord-derived tissues and neoplasms, and has become a defining immunohistochemical feature of chordoma. The main differential diagnostic consideration for chordoma is chondrosarcoma, which is known to lack brachyury expression. However, within the spectrum of genitourinary neoplasia, metastatic germ cell tumors and clear cell renal cell carcinoma may also be close morphological mimics of chordoma, particularly given the increasing prevalence of small tissue samples from image-guided biopsies. Although immunoreactivity for brachyury has been reported in a few germ cell tumors, a thorough characterization of staining by specific subtype has not been performed in a large series. Additionally, brachyury expression in clear cell renal cell carcinoma has not been well studied. In this study, immunohistochemical expression with the brachyury antibody was evaluated in 111 germ cell tumors, 30 non-neoplastic and neoplastic (non-germ cell) testicular tissues, and 184 metastatic clear cell renal cell carcinomas using tissue microarray technology. In addition, immunoreactivity for PAX-8 and SALL-4 was evaluated in 12 chordomas on whole section. No nuclear brachyury expression was identified in any of the 101 germ cell tumors within the tissue microarray (including choriocarcinoma (1), embryonal carcinoma (20), intratubular germ cell neoplasia unclassified (2), seminoma (64), spermatocytic seminoma (1), teratoma (5) and yolk sac tumor (8)), in any of the 30 non-neoplastic and neoplastic (non-germ cell) testicular tissues, or in any of the 10 whole-section seminomas. All 184 metastatic clear cell renal cell carcinomas were also non-reactive for brachyury. All 12 chordomas showed strong nuclear immunoreactivity for brachyury, but no expression of SALL-4. In all, 1 of 12 chordoma cases showed patchy, 1+ nuclear immunoreactivity for PAX-8. This study confirms the specificity of brachyury for chordoma in the differential diagnostic distinction from the potential genitourinary mimics, germ cell tumors and metastatic clear cell renal cell carcinoma.

Chest wall tumors in childhood and adolescence

Chest wall tumors in childhood and adolescence can be very heterogeneous and may appear at any age from infancy to late adolescence. They can be benign or malignant and secondary or primary. A careful history and physical examination should be followed by adequate imaging studies to delineate the primary tumor and identify possible sites of dissemination. Diagnosis usually requires either a needle or open biopsy which minimizes dissection so that a complete resection can be done later. Most neoplastic lesions require a complete resection, whereas secondary and infectious processes are treated with chemotherapy or antibiotics. Rigid chest wall re-construction has the advantage of eliminating paradoxical respiration and obviating the need for postoperative ventilation. Another advantage is maintenance of chest wall contour.

Dedifferentiated chordoma of the thoracic spine with rhabdomyosarcomatous differentiation. Report of a case and review of the literature

A case of spinal thoracic chordoma involving the T9 vertebra in a 70-year-old male patient, destroying the vertebral body and invading the vertebral canal with compression of the spinal cord, is presented. The patient was referred to our neurosurgical unit with a history of an irradiated metastatic adenocarcinoma to the thoracic vertebra, a diagnosis that was rendered 3 years earlier at another hospital on presentation. This misdiagnosis was likely due to the absolute rarity of thoracic vertebral chordomas (2%-3% of all chordomas), the higher frequency of metastatic deposits to the vertebrae from visceral cancers in the elderly, the limited amount of biopsy material available for histologic examination, and the epithelial phenotype of the tumor (keratin/EMA positive). The patient underwent second palliative surgery with subtotal piecemeal removal of the tumor bringing relief of the neurologic symptoms. The bulk of the tumor was represented by a high-grade pleomorphic sarcoma with adjacent areas of atypical chordoma. Small foci of conventional chordoma were also found. The previous histologic slides were also reviewed, which were consistent with the areas of atypical chordoma. Small targeted tissue fragments from areas of (atypical) chordoma and from sarcomatous areas were recovered for electron microscopy. The fine features of chordoma and focal rhabdomyoblastic differentiation were found with the latter retrospectively supported by immunohistochemical detection of striated muscle markers. A final diagnosis of dedifferentiated chordoma with rhabdomyoblastic differentiation was finally established. Rhabdomyoblastic metaplasia is a novelty in dedifferentiated chordoma. The patient died after 5 months. Autopsy was not requested.

Imaging features of posterior mediastinal chordoma in a child

A 5 1/2-year-old boy presented with repeated episodes of stridor and cough. Chest radiography demonstrated a widened mediastinum. Evaluation by CT revealed a low-density posterior mediastinal mass initially diagnosed as benign tumor. Histopathological analysis of the resected mass disclosed a malignant chordoma. Our radiological results are described with an analysis of the imaging findings in the medical literature. We present our suggestions for preoperative evaluation of posterior mediastinal tumors.

Myxopapillary ependymoma of the posterior mediastinum

A left paravertebral mass discovered incidentally on routine examination in a 39-year-old woman is described. Computerized tomography studies revealed a 7 x 6 cm, well circumscribed, noncalcified soft tissue mass with lobular borders abutting the left inferior pulmonary vein and descending aorta. It was not possible to determine the exact anatomic location of the mass based on the imaging studies as both peripheral lung tumors and posterior mediastinal lesions may exhibit the imaging findings described here. At thoracotomy, the mass was seen to be well circumscribed, focally attached to the pleura but without involvement of lung parenchyma, and situated in the left posterior mediastinum. On histological examination, the lesion showed the classical features of myxopapillary ependymoma. Immunohistochemical studies confirmed this impression by demonstrating strong positivity of the tumor cells for S-100 protein, glial fibrillary acidic protein, and CD99 and negative staining with other differentiation markers. A review of the literature with a discussion of the histologic and radiologic differential diagnosis of these lesions is presented.

Soft tissue sacrococcygeal chordoma with intracytoplasmic filamentous inclusions

Extraskeletal chordoma arising within soft tissue is a rare occurrence. We report a case of chordoma that is unusual both for its location within the subcutaneous soft tissue of the sacrococcygeal region without involvement of adjacent bones and for the presence of eosinophilic roundish inclusion bodies within the cytoplasm of tumor cells. These bodies revealed immunoreactivity for cytokeratin and a fibrillar, partly whorled structure on the electron microscopic examination, consistent with an intermediate filament-based composition. To our knowledge, this is the first report of chordoma featuring this cellular change although we do not know the significance of these bodies.

Epithelioid cellular chordoma of the sacrum: a potential diagnostic problem

We describe a sacral chordoma composed of solid nests of epithelioid cells. The tumor originated in the presacral area. Extensive clinical workup did not reveal any other lesion in the patient. In contrast to typical chordomas, this tumor contained only rare physaliferous cells, had no myxoid stroma, and was immunohistochemically unreactive with the antibody to S-100. The diagnosis of chordoma was supported by electron microscopy, which showed that the tumor cells contained numerous mitochondria surrounded by profiles of rough endoplasmic reticulum. The abundance of mitochondria, the narrow intercellular spaces, combined with a lack of glycogen, and a lack of extracellular myxoid material accounted for the epithelioid appearance of the tumor. We report this case to point out that the cellular chordomas can appear epithelioid in the sacrum and they may resemble metastatic squamous or transitional cell carcinomas.

Uncommon primary mediastinal tumours

The mediastinum is a unique anatomic area containing several structures and pluripotent cells that allow for the development of a range of tumours. Uncommon neoplasms of the mediastinum account for less than 10% of all mediastinal masses and include primary thymic carcinomas, neuroendocrine carcinomas, germ-cell tumours (GCTs), lymphomas, and neurogenic, endocrine, and mesenchymal tumours. Primary thymic carcinomas and neuroendocrine carcinomas, although rare, are highly malignant lesions. GCTs are thought to derive from primitive germ cells and can be classified in seminomatous and non-seminomatous GCTs. They are located predominantly in the anterior mediastinum, as are the primary mediastinal lymphomas that include Hodgkin lymphoma, large B cell lymphoma, and lymphoblastic lymphoma. Neurogenic tumours may arise from peripheral nerves, sympathetic ganglia, or rarely parasympathetic ganglia and are located predominantly in the posterior mediastinum. Endocrine tumours are the ectopic thyroid and parathyroid tumours. Mesenchymal tumours are rare tumours and no less problematic than they are in peripheral sites. The clinical, radiological, and therapeutic aspects of these tumours are reviewed.

Unusual presentation of posterior mediastinal chordoma in a 2-year-old boy

Chordoma is a rare and slow-growing malignant neoplasm that arises from the embryonic notochord. It is rare to see a thoracic chordoma presenting as a posterior mediastinal mass with pleural seeding in a child. The authors report a chordoma of the thoracic spine with posterior mediastinal extension and pleural seeding in a 2-year-old boy who presented with asymmetric bilateral hand temperature and lower limb paralysis. The clinical course progressed rapidly, resulting in death.

Clear cell atypical fibroxanthoma:a clinicopathologic study

INTRODUCTION

The atypical fibroxanthoma (AFX) is considered by most authorities to represent a superficial or minimally invasive variant of malignant fibrous histiocytoma that most often presents as a solitary nodule on the sun-exposed skin of the elderly. Among the rarest variants is the clear cell AFX, a lesion which raises consideration to a differential diagnosis encompassing a variety of neoplastic and non-neoplastic clear cell proliferations.

METHODS

We describe three cases of a distinctive cutaneous neoplasm arising in the sun-exposed skin of elderly patients. In all cases, formalin-fixed, paraffin-embedded tissue was available for analysis. The histology in concert with the immunophenotype was held to be diagnostic of the clear cell variant of AFX.

RESULTS

All tumors comprised sheets of large cells with foamy cytoplasms and hyperchromatic, polyploid nuclei manifesting frequent and atypical mitoses. The critical cells in our cases expressed CD68 but none of CD3, CD20, CD34, S-100 protein, muscle-specific actin, factor XIIIa, Melan-A, carcinoembryonic antigen, or cytokeratin.

CONCLUSION

Although typical examples of AFX provoke diagnostic consideration of spindle cell cancers of the skin (most often spindle cell melanoma, spindle cell squamous cell carcinoma, and leiomyosarcoma), the clear cell variant raises other differential diagnostic considerations instead. These include balloon cell melanoma, sebaceous carcinoma, pleomorphic liposarcoma, chordoma, parachordoma, tricholemmal carcinoma and clear cell squamous cell carcinoma. A diagnosis of AFX is one of exclusion; one must employ immunohistochemical markers to rule out the aforementioned differential diagnostic considerations. By reporting the fifth, sixth and seventh cases of clear cell AFX, we hope to alert dermatopathologists to this distinctive and unusual neoplasm, recognition of which is essential to avoid under- or over-diagnosis and inappropriate therapy.

Myxoma is not a single entity: a review of the concept of myxoma

Myxoid lesions can be subdivided into (1) mainstream myxomas of soft tissues, (2) mainstream myxomas located outside the soft tissue, (3) inadequately substantiated myxomas, (4) myxoid soft tissue tumors or lesions not regarded as myxomas, (5) myxoid fatty conditions, (6) other soft tissue lesions and tumors that are sometimes markedly myxoid, (7) other soft tissue tumors in which myxoid foci may be seen, and (8) nonneoplastic myxoid conditions of soft tissue. More than 60 such conditions are listed and the five entities regarded as mainstream soft tissue myxomas (namely, intramuscular myxoma, juxta-articular myxoma, superficial angiomyxoma, aggressive angiomyxoma, and myxoid neurothekeoma [myxoma of nerve sheath]) are reviewed in detail. Intramuscular myxoma is exclusively intramuscular, usually affects middle-aged women, is most commonly located in the thigh, and does not recur after simple excision. Multiple intramuscular myxomas are rare and are usually associated with monostotic or polyostotic fibrous dysplasia and Albright's syndrome. Juxta-articular myxoma histologically resembles an intramuscular myxoma, but involves periarticular tendons, ligaments, joint capsules, muscles, and even the subcutis of adults. It may be associated with osteoarthritis of the adjacent joint. Some 30% recur locally. Superficial angiomyxoma also has been called cutaneous myxoma. It affects all ages, with a peak incidence in the third and fourth decades; arises in the trunk, lower limb, head, and neck regions; and usually measures less than 5 cm in diameter. Epithelial components are present in approximately 25% of tumors. Approximately one third recur locally, but there have been no metastases. Patients with multiple lesions may have the Carney complex. Aggressive angiomyxoma usually arises in the pelvic and perineal regions and affects females seven times as often as males. Tumors usually measure 10 cm or more in diameter, invade surrounding tissues, and recur in approximately 50% of cases. None have metastasized. Myxoma of nerve sheath (the myxoid variant of neurothekeoma) preferentially affects the dermis and subcutis of the cervicofacial areas and shoulders of young women. Most patients are younger than 40 years; one third of them are in the second decade of life. The majority of tumors measure between 0.5 and 1.5 cm. Only three of 102 cases compiled from the two largest published series recurred; none metastasized. The different clinicopathologic features and behavior of these five mainstream myxomas indicate that myxoma is not a single entity.

Chondroid chordoma: fine-needle aspiration cytology with histopathological, immunohistochemical, and ultrastructural study of two cases

Chondroid chordoma is a controversial and confusing entity that was originally described by Heffelfinger et al. (Cancer 1973; 32:410-420) as a biphasic malignant neoplasm possessing elements of both chordoma and cartilaginous tissue. Fine-needle aspiration (FNA) cytology of chondroid chordoma has not been described. The aim of our investigation was to characterize the chondroid area of chondroid chordoma and to compare the FNA features with those of well-differentiated chondrosarcoma. Clival and cervical spine chondroid chordomas were studied with light microscopy, immunohistochemistry, and electron microscopy. Chondroid chordomas demonstrated an epithelial nature by immunohistochemistry and ultrastructural studies. The FNA smears showed low cellularity, with loosely arranged or dispersed round cells in a myxoid background. Although the smears were similar to those of well-differentiated chondrosarcomas, they showed a positive reaction for epithelial markers. These findings reveal that chondroid chordoma is a variant of chordoma which possesses a hyaline matrix. Immunohistochemical demonstration of epithelial markers is useful to distinguish it from chondrosarcoma. Diagn. Cytopathol. 1999; 21:335-339.

Cutaneous parachordoma. A light microscopic and immunohistochemical report of two cases and review of the literature

Parachordomas are rare cutaneous tumors that show virtually identical histologic findings to chordomas. Therefore, the major differential diagnosis in a case of parchordoma is metastatic chordoma. Parachordomas are benign neoplasms and most often develop on the extremities adjacent to tendons, synovium or osseous structures, as opposed to chordomas, which are malignant tumors located along the craniospinal axis. While recurrences may occur in cases of parachordoma, metastases have not been reported. In this report, two cases of parachordomas are reported and the literature reviewed. By light microscopy, parachordomas show eosinophilic bands of fibrous tissue separating lobules of cells with variably vacuolated cytoplasm (physaliphorous cells) admixed with more epithelioid cells in a myxoid stroma. Parachordomas and chordomas share immunohistochemical and ultrastructural features. Both stain with S-100 protein and vimentin, and ultrastructurally both demonstrate cytoplasmic vacuoles, intermediate filaments, pinocytotic vesicles, celljunctions, and cytoplasmic membranes with microvillous processes. Chordomas more frequently express cytokeratin (98% vs. 66% in parachordomas) and epithelial membrane antigen (90% vs. 20% in parachordomas) and chordomas have a larger number of rough endoplasmic reticulum-mitochondrial complexes. Thus, positive staining with epithelial membrane antigen and the identification of a large number of rough endoplasmic reticulum-mitochondrial complexes are suggestive of metastatic chordoma. However, the definitive distinction remains a clinical one after appropriate radiologic studies of the skull and spinal chord.

Malignant cartilaginous tumors of the mediastinum: clinicopathological study of six cases presenting as extraskeletal soft tissue masses

Cartilage and bone-forming tumors of the mediastinum are extremely rare neoplasms with very few cases having been reported in the literature. We studied six cases of primary malignant cartilaginous tumors presenting as extraskeletal soft tissue masses in the posterior mediastinum. The patients were five women and one man aged 11 to 63 years (median, 31 years). Histologically, the lesions showed a spectrum of features that ranged from mesenchymal chondrosarcoma, to extraskeletal myxoid chondrosarcoma, to moderately well to poorly differentiated chondrosarcoma. In all cases, the lesions presented as well-circumscribed tumor masses centered in the soft tissues in the posterior mediastinum without radiographic evidence of origin from bone. Because of their relatively small size, good circumscription, focal areas of calcification, and posterior mediastinal location, the preoperative clinical diagnoses included benign neurogenic tumor and neuroblastoma. All of the lesions were treated by complete surgical excision, followed in two cases by postoperative radiation therapy. Clinical follow-up was available in five cases: two patients with mesenchymal chondrosarcoma presented with local recurrence after 3 and 7 years, one developed metastases to the sacrum 8 years after initial diagnosis and died, and one was alive and well without evidence of disease after 6 years. The patient with myxoid chondrosarcoma of the posterior mediastinum developed bilateral pulmonary metastases 10 months after surgery and has been lost to follow-up since. Our findings reinforce previous observations on the occurrence of extraskeletal cartilaginous tumors in the mediastinum and indicate that these tumors can show a propensity for local aggressive behavior with high recurrence rate and a definite potential for distant metastases. Such tumors should be considered in the differential diagnosis of malignant neoplasms presenting as a soft tissue mass in the posterior mediastinum.