Parachordoma: a clinicopathologic and immunohistochemical study of four cases of an unusual soft tissue neoplasm

Myoepithelioma-like Hyalinizing Epithelioid Tumors of the Hand With Novel OGT-FOXO3 Fusions

Myoepithelial tumors of soft tissue are uncommon neoplasms characterized histologically by spindle to epithelioid cells arranged in cords, nests, and/or reticular pattern with chondromyxoid to hyaline stroma, and genetically by rearrangement involving EWSR1 (among other less common genes) in about half of the cases. The diagnosis often requires immunostaining to confirm myoepithelial differentiation, most importantly the expression of epithelial markers and S100 protein and/or GFAP. However, there are cases wherein the morphology is reminiscent of myoepithelial tumors, while the immunophenotype falls short. Here, we report 2 highly similar myoepithelioma-like tumors arising in the hands of young adults. Both tumors were well-demarcated and composed of alternating cellular areas with palely eosinophilic hyaline stroma and scattered acellular zones of densely eosinophilic collagen deposition. The tumor cells were mainly epithelioid cells and arranged in cords or small nests. Vacuolated cells encircling hyaline matrix globules were focally prominent. A minor component of nonhyaline fibrous nodular areas composed of bland spindle cells and rich vasculature was also observed. Perivascular concentric spindle cell proliferation and perivascular hyalinization were present in some areas. The tumor cells were positive for CD34 and epithelial membrane antigen (focal) by immunostaining, while largely negative for cytokeratin, S100, GFAP, p63, GLUT1, and claudin-1. By RNA sequencing, a novel OGT-FOXO3 fusion gene was identified in case 1 and confirmed by reverse transcription polymerase chain reaction and fluorescence in situ hybridization in both cases. Sharing the unusual clinicopathologic features and the novel fusion, these 2 cases probably represent a distinct tumor entity, whose relationship with myoepithelial tumors and tumorigenic mechanisms exerted by the OGT-FOXO3 fusion remain to be studied.

Diagnostic histochemistry of soft tissue lesions

Histochemical methods (HM) were, at one time, extensively used in all facets of anatomic pathology, including analysis of soft tissue lesions. That situation has changed with the advent of other adjunctive procedures, but HM still do contribute meaningfully to the evaluation of several tumefactive conditions in the soft tissue. This brief review considers selected neoplastic, quasineoplastic, and pseudoneoplastic lesions in that category, with emphasis on their histochemical properties.

Recurrent parachordoma of the lower back: A case report

Parachordoma is a rare entity with less than 50 cases described in the literature. This soft-tissue tumor resembles chordomas as well as extraskeletal myxoid chondrosarcomas and has only recently been fully characterized. Here we describe the case of a patient with a lower back parachordoma and its subsequent postresection recurrence 9 years after the initial procedure, emphasizing the importance of long-term follow-up in individuals with this diagnosis.

Parachordoma: A Case Report

Parachordoma is a very rare soft tissue tumor with histological features similar to chordoma and chondrosarcoma. It should be distinguished from metastatic chordoma and extraskeletal myxoid chondrosarcoma because of its different treatment and prognosis. In this paper we report one case of parachordoma in a 20-year-old female patient. The tumor occurred in the subcutaneous tissue of the left hand as a painless, fixed, slow-growing mass. Pathologic analysis revealed a tumor composed of lobules of cells with variably vacuolated cytoplasm (physaliphorous cells) separated by fibrous septa, predominantly arranged in peculiar small or large alveolar structures. Immunohistochemistry showed positive staining of the tumor cells with cytokeratin 8/18, S-100 protein and vimentin. The patient is well and without recurrence 20 months after surgery.

Extra-axial chordomas

INTRODUCTION

A chordoma is a slow growing malignant tumour of notochordal origin. A tumour with histological features that are identical to those of a chordoma may arise outside the axial skeleton. To date, there is little in the literature documenting their clinical course.

METHODS

Our large orthopaedic oncology database was used to document the clinical course of extra-axial chordoma.

RESULTS

Over a 30-year period, 131 patients diagnosed with a chordoma were treated at our unit. Only three (2.3%) of these cases were extra-axial chordomas: one in the femur, one in the ulna and one in the proximal fibula. All underwent surgical resection.

CONCLUSIONS

In view of the rarity of this tumour and the difficulty in confirming its diagnosis, we suggest that any suspected case is discussed with a specialist sarcoma multidisciplinary team so that the correct diagnosis can be achieved and treatment tailored accordingly.

Epithelioid Sarcoma: Diagnostic Features and Genetics

Epithelioid sarcoma (ES) is a rare, aggressive soft-tissue neoplasm of uncertain differentiation, characterized by nodular aggregates of epithelioid cells, which are immunoreactive to cytokeratins (CKs) and epithelial membrane antigen, and often for CD34. It has a propensity for multifocal disease at presentation, local recurrence, and regional metastasis. These are aggressive neoplasms with particularly poor prognosis after regional or distant metastatic disease, for which surgical resection is still the mainstay of treatment, and options for patients with metastatic disease remain undefined. There are 2 distinct variants: classic ES, which typically presents as a subcutaneous or deep dermal mass in the distal extremities of young adults and comprises nodular distributions of relatively uniform epithelioid cells with central necrosis, and the proximal variant, which has a predilection for proximal limbs and limb girdles and the midline of the trunk, which is composed of sheets of larger, more atypical cells with variable rhabdoid morphology. Both classic and proximal-type ESs are associated with the loss of SMARCB1/INI1 protein expression, but appear otherwise molecularly relatively heterogeneous. We review classic and proximal-type ES, discussing morphology, immunohistochemical and genetic findings, the differential diagnosis, and the future potential for targeted therapies.

Primary intracranial Parachordoma: An unusual tumor in brain

Background:

Parachordomas are rare soft tissue tumors commonly occurring in limbs, chest, Abdomen, and back. The World Health Organization (WHO) classification includes parachordomas in the same group as mixed tumors and myoepitheliomas. Exact histogenesis of this tumor is unclear.

Case Description:

A 52-year-old male presented with headache and blurring of vision since one month. Preoperative computed tomography (CT) scan of brain revealed left parieto-occipital tumor extending up to the trigone. Total excision of the tumor was done. Histopathologically, the tumor was composed of relatively uniform cells with eosinophilic cytoplasm in a myxoid stroma and with cartilaginous and osseous metaplasia. The tumoral cells were immunoreactive for cytokeratin, epithelial membrane antigen (EMA), S-100, and vimentin. The constellation of findings revealed the tumor to be parachordoma. Magnetic resonance imaging (MRI) brain during follow-up at one year showed no recurrent tumor. No adjuvant therapy was given to this patient.

Conclusion:

This is the first reported case of primary intracranial parachordoma. It is difficult to diagnose the lesion preoperatively by imaging alone. Long-term follow-up is necessary in view of few reports in literature of recurrence and metastasis, of parachordomas in other anatomical locations.

Myoepithelial tumor of soft tissue: histology and genetics of an evolving entity

Myoepithelial neoplasms represent a heterogeneous group of tumors of which classification is incomplete and evolving. Those of the soft tissues often form genetically distinct subgroups that differ from those arising within salivary glands. Soft-tissue myoepithelial tumors (including mixed tumors that show true glandular or ductal differentiation) exhibit a spectrum of different morphologic patterns, making them difficult to distinguish from a variety of other neoplasms. They have been increasingly shown to harbor genetic fusions involving EWSR1 and partner genes that are not seen in the well-characterized tumor classes involving EWSR1 translocations. We review the spectrum of soft-tissue myoepithelial tumors, discussing recent immunohistochemical and genetic findings and the differential diagnosis.

Brachyury: a diagnostic marker for the differential diagnosis of chordoma and hemangioblastoma versus neoplastic histological mimickers

Brachyury is a transcription factor which is required for posterior mesoderm formation and differentiation as well as for notochord development during embryogenesis. Due to its expression in the neoplastic cells of chordoma, a malignant tumour deriving from notochordal remnants, but not in tumors showing a similar histology, brachyury has been proposed as a diagnostic marker of this neoplasia. Though commonly considered a hallmark of chordoma, the expression of brachyury has been also documented in the stromal cells of hemangioblastoma (HBL), a slow growing tumor which may involve the central nervous system (CNS) and, rarely, the kidney. Herein we review the role of brachyury immunohistochemical detection in the identification and differential diagnosis of chordoma and HBL towards histological mimickers and suggest that brachyury is added to the panel of immunohistochemical markers for the recognition of HBL in routinary practice, principally in unusual sites.

Recently characterized soft tissue tumors that bring biologic insight

Previously unrecognized but clinicopathologically (and often molecularly) distinct types of soft tissue tumor continue to be characterized, allowing wider recognition, more consistent application of diagnostic criteria, more reliable prediction of tumor behavior and enhancement of existing classification schemes. Examples of such 'entities' that have become much better understood over the past decade or so include deep 'benign' fibrous histiocytoma, hemosiderotic fibrolipomatous tumor, PEComa, spindle cell liposarcoma, myoepithelial tumors of soft tissue and spindle cell/sclerosing rhabdomyosarcoma. These tumor types, as well as the insights which they have engendered, are briefly reviewed here.

Recurrent skeletal extra-axial chordoma confirmed with brachyury: imaging features and review of the literature

A small number of tumors bearing histological resemblance to axial chordoma arising from the bone or soft tissue outside the axial skeleton have been reported. These lesions have historically been referred to as parachordoma, chordoma periphericum (CP), or extra-axial chordoma (EAC). With the introduction of the immunohistochemical stain brachyury, a sensitive and specific marker for notochordal origin, chordomas arising in extra-axial locations (i.e., CP, EAC), are now diagnosed with more accuracy and distinguished from parachordoma, which resembles chordoma on histology. The distinction between EAC and parachordoma is clinically important because EAC confirmed by immunoreactivity for brachyury tends to grow and recur with local bone destruction. Prior to the introduction of brachyury, the diagnosis of EAC was challenging and therefore the imaging features of EAC have not been comprehensively described. We report two cases of recurrent EAC confirmed by the expression of brachyury arising from the distal femur and distal tibia and describe the imaging findings from radiography and MRI at initial diagnosis and at recurrence.

Parachordoma of soft tissues of the arm: a very rare tumour

Parachordoma is an infrequent neoplasm that bears some histologic resemblance to chordoma. It affects both sexes, occurs typically during the fourth decade of life, and tends to present as a slow-growing painless mass at the level of the soft tissues of the extremities. Diagnosis should be based on immunohistochemical and cytogenetic studies, as the findings of imaging techniques are often unspecific. Although it is considered a benign lesion, its behavior tends to be locally aggressive, with reports of a recurrence rate of up to 20% and of several cases of metastasis. Fewer than 60 cases have been published in the English-speaking literature. In this paper we present the case of a 32-year-old male with a two-year history of parachordoma in the right wrist.

Primary pulmonary myxoid sarcoma with EWSR1-CREB1 fusion: a new tumor entity

We present clinicopathologic data on 10 pulmonary myxoid sarcomas, which are defined by distinctive histomorphologic features and characterized by a recurrent fusion gene, that appear to represent a distinct tumor entity at this site. The patients [7 female, 3 male; aged 27 to 67 y (mean, 45 y)] presented with local or systemic symptoms (n=5), symptoms from cerebral metastasis (1), or incidentally (2). Follow-up of 6 patients showed that 1 with brain metastasis died shortly after primary tumor resection, 1 developed a renal metastasis but is alive and well, and 4 are disease free after 1 to 15 years. All tumors involved pulmonary parenchyma, with a predominant endobronchial component in 8 and ranged from 1.5 to 4 cm. Microscopically, they were lobulated and composed of cords of polygonal, spindle, or stellate cells within myxoid stroma, morphologically reminiscent of extraskeletal myxoid chondrosarcoma. Four cases showed no or minimal atypia, 6 showed focal pleomorphism, and 5 had necrosis. Mitotic indices varied, with most tumors not exceeding 5/10 high-power fields. Tumors were immunoreactive for only vimentin and weakly focal for epithelial membrane antigen. Of 9 tumors, 7 were shown to harbor a specific EWSR1-CREB1 fusion by reverse transcription-polymerase chain reaction and direct sequencing, with 7 of 10 showing EWSR1 rearrangement by fluorescence in situ hybridization. This gene fusion has been described previously in 2 histologically and behaviorally different sarcomas: clear cell sarcoma-like tumors of the gastrointestinal tract and angiomatoid fibrous histiocytomas; however, this is a novel finding in tumors with the morphology we describe and that occur in the pulmonary region.

Possible parachordoma in a dog

CASE HISTORY

A 15-mm diameter mass developed in the S/C tissue overlying the right lateral gluteal muscle of a 6(1/2)-year-old female Flat-coated Retriever.

PATHOLOGICAL FINDINGS

Cytological preparations following aspiration of the mass were highly cellular and consisted of a population of large polygonal cells containing single to multiple nuclei, large prominent nucleoli, and intracytoplasmic vacuoles. Histologically, the neoplasm consisted of similar large cells surrounded by thick fibrous connective tissue trabeculae. The large polygonal cells reacted positively with antibodies against vimentin, low- and high-molecular-weight variants of cytokeratin (AE1/AE3), but not with antibodies to desmin or glial fibrillary acidic protein (GFAP).

DIAGNOSIS

The clinical, gross, histological and immunohistochemical findings are similar to those reported for parachordomas in humans. Neither recurrence nor metastases were noted 18 months after surgical excision of the mass.

CLINICAL RELEVANCE

This is the first reported case of a possible parachordoma in a dog, a benign tumour with cytological features of malignancy.

Myoepithelioma within the carpal tunnel: a case report and review of the literature

Myoepitheliomas of the extremity are rare and usually benign, while a minority display malignant features. This case demonstrates the diagnosis and management of myoepithelioma within the carpal tunnel. Clinical and radiological tumour features were evaluated. Hematoxylin and eosin stained tumour sections were examined, and immunohistochemistry was performed. Histology revealed a nodular mass of epithelioid cells in clusters within a myxoid/chondroid stroma. No mitoses were noted. Cytokeratins, neuron-specific enolase, synaptophysin, glial fibrillary acidic protein, and S100 were positive on immunohistochemistry. A literature review revealed very few prior reports of myoepithelioma in the wrist, and limited data concerning any relationship between recurrence and quality of surgical margins. In this case, wide local excision would have significantly compromised dominant hand function, and therefore a marginal excision was deemed appropriate in the context of bland histological features. Surgical margins noted in future case reports will aid clinical decision making.

Pulmonary metastases from parachordoma

A young woman was referred to our institution for the appearance of a single pulmonary nodule at a routine follow-up computed tomographic scan of the thorax. She had been operated on 4 years earlier for a parachordoma of the iliopsoas muscle. Wedge resections were accessed through a mini-thoracotomy, and the pathologic examination confirmed the diagnosis of parachordoma lung metastases. Adjuvant chemotherapy (Glivec, 400 mg/daily [imatinib; Novartis, Basel, Switzerland]) was indicated and was administered for 10 months. At the time this case report was written, the patient was alive with no sign of tumor recurrence. We believe that metastatic parachordoma to the lung has been previously reported only once in the English literature. Our case adds evidence that parachordoma, despite its generally indolent behavior, can metastasize to the lung.

Case report: parachordoma of soft tissues of the arm

Parachordoma, or myoepithelioma, is a very rare tumor histologically resembling chordoma but occurring in the nonaxial soft tissues. It typically has an indolent nature, with occasional late recurrence and even rare metastases. Review of existing literature reveals a male predilection, with the tumor typically occurring in the fourth decade of life in the lower extremity. It typically is managed with wide resection. We report the case of a 60-year-old woman with a right distal upper arm parachordoma treated with wide resection of the tumor.

Parachordoma of the gastric serosa: report of a myxoid mimicry in an unusual location

The authors report a case of an incidentally discovered myxoid stromal tumor occurring in the outer wall of the stomach of a 65-year-old woman. The tumor was phenotypically consistent with parachordoma (or myoepithelioma), showing a chordoid microscopic appearance of tumor cells loosely arranged within a myxoid or hyaline background. Immunoreactivity for high-molecular-weight keratins, S100 protein, and vimentin was detected. In this report, the authors address the differential diagnosis of parachordoma and the unusual location of this neoplasm.

Diagnosing an extra-axial chordoma of the proximal tibia with the help of brachyury, a molecule required for notochordal differentiation

Chordomas are rare malignant bone tumours considered to arise from notochordal remnants that persist in the axial skeleton. Although their morphology can resemble that of a carcinoma, chondrosarcoma or malignant melanoma, the axial location and their well-defined immunophenotype, including expression of cytokeratins (CK7/20/8/18/19) and S100, generally allow the diagnosis to be made with confidence once the possibility is considered. In contrast, making a robust diagnosis of an extra-axial chordoma has been difficult in the absence of specific markers for chordomas. We have recently shown in gene expression microarray and immunohistochemistry studies that brachyury, a transcription factor crucial for notochordal development, is a specific and sensitive maker for chordomas. We now present a case of an intracortical tibial tumour, with detailed report of the imaging, and morphological features consistent with a chordoma, where notochordal differentiation was demonstrated with an antibody to brachyury. The tumour cells were also positive for cytokeratins, including CK19, and S100, CEA, EMA and HMBE1, findings which support the diagnosis of chordoma. Brachyury can be employed as a marker of notochordal differentiation and help identify confidently, for the first time, extra-axial bone and soft tissue chordomas, and tumours which may show focal notochordal differentiation.

Extra-Axial Chordoma

Chordomas are low-grade malignant tumors of bone that occur almost exclusively in the axial skeleton. Other neoplasms with a similar histologic picture but an extra-axial location have been described, including parachordoma, myxoid chondrosarcoma, and extra-axial chordoma. We herein present another case of the rare extra-axial chordoma. A 41-year-old woman developed an 8.3 cm mass in the pubic bone. The gross, microscopic, and immunohistochemical findings were identical to those of a classic chordoma. Parachordoma and myxoid chondrosarcoma were excluded from the differential diagnosis. Five previously reported cases of extra-axial chordoma were reviewed and found also to demonstrate clinical and pathologic features specific to chordoma, despite arising in an extra-axial location. Although rare, extra-axial chordoma does exist and should be recognized and managed in a similar fashion to its well-described counterpart. It must be differentiated from other histologic mimics, because the treatment and prognosis can differ significantly.

Unusual variants of malignant melanoma

A potential diagnostic pitfall in the histologic assessment of melanoma is the inability to recognize unusual melanoma variants. Of these, the more treacherous examples include the desmoplastic melanoma, the nevoid melanoma, the so-called 'minimal-deviation melanoma,' melanoma with prominent pigment synthesis or 'animal-type melanoma,' and the malignant blue nevus. Also problematic are the unusual phenotypic profiles seen in vertical growth phase melanomas; these include those tumors whose morphological peculiarities mimic cancers of nonmelanocytic lineage and those melanomas that express aberrant antigenic profiles not commonly associated with a melanocytic histogenesis. Metaplastic change in melanoma, balloon cell melanoma, signet-ring cell melanoma, myxoid melanoma, small cell melanoma and rhabdoid melanoma all have the potential to mimic metastatic and primary neoplasms of different lineage derivations. Abnormal immunohistochemical expression of CD 34, cytokeratins, epithelial membrane antigen, and smooth muscle markers as well as the deficient expression of S100 protein and melanocyte lineage-specific markers such as GP100 protein (ie HMB-45 antibody) and A103 (ie Melan-A) also present confusing diagnostic challenges. In this review, we will discuss in some detail certain of these novel clinicopathologic types of melanoma, as well as the abnormal phenotypic expressions seen in vertical growth phase melanoma.

[Myoepithelioma of soft tissue -- case report with clinicopathologic, ultrastructural, and cytogenetic findings]

The case of a soft tissue myoepithelioma is presented including clinicopathologic, ultrastructural, and genetic findings. A 30-year-old male patient suffered from a soft tissue tumor within the deep soft tissues of the right lower leg measuring 13.2 x 8.2 x 9 cm. Histologically, the lesion was diagnosed as a myoepithelioma displaying a lobulated architecture with cords and nests of epithelioid and spindle cells without cytologic atypia lying within a fibromyxoid and partly chondroid matrix; immunohistochemistry was positive for pancytokeratin, S100-protein, calponin and partly for GFAP and EMA. Ultrastructural analysis revealed glycogen deposits and cell-membrane-associated plaque structures, whereas true myofilaments could not be identified (with immunohistochemistry being negative for actin). Using comparative genomic hybridization (CGH), a gain of chromosome Y was detected. A loss on 17p could not be detected unambiguously. However, based on the low resolution of CGH a small loss cannot be excluded. The patient was free of disease 25 months following complete tumor resection. Myoepitheliomas/mixed tumors of deep soft tissue represent rare soft tissue lesions that may reach a considerable size and may mimic other soft tissue tumors or sarcomas. Based on a local relapse rate of approximately 20% according to the literature, a complete resection with thorough follow-up should be recommended.

Parachordoma is not distinguishable from axial chordoma using immunohistochemistry

Parachordoma is a rare soft tissue tumor that morphologically resembles chordoma of the axial skeleton but occurs in a peripheral site. A recent study reported immunohistochemical differences between chordoma and parachordoma. While both tumors were positive for cytokeratin (CK) 8/18 (as recognized by the antibody Cam5.2), S100 and epithelial membrane antigen (EMA), only the chordoma was positive for CK7, CK20, CK 1/5/10/14 (as recognized by the antibody 34betaE12) and carcinoembryonic antigen (CEA). It has since been suggested that tumors indistinguishable from chordoma that involve the periphery should be termed chordoma periphericum and that these tumors are distinct from parachordoma. In the current study, the clinical, radiological, pathological, immunohistochemical and ultrastructural features of a chordoma-like tumor involving the deep soft tissues of the lower leg of a 69-year-old woman are presented. Microscopically, the tumor had a pseudolobulated growth pattern and consisted of sheets, nests and cords of epithelioid cells, some with a physaliferous appearance, separated by abundant myxoid stroma. The tumor cells were positive for CK 8/18, EMA and S100, showed focal staining for CK7, and were negative for CK20, CK 1/5/10/14 and CEA. On the basis of these results a diagnosis of parachordoma was favored. For comparison, an immunohistochemical analysis of five axial chordomas was also performed. The chordomas showed positivity for CK 8/18 (5 of 5 cases), EMA (5 of 5 cases), S100 (5 of 5 cases), CK 1/5/10/14 (1 of 5 cases) and CK7 (1 of 5 cases). Stains for CK20 and CEA were negative in all five chordomas. The results of the present study suggest that the expression of antigens for CK 1/5/10/14, CK7, CK20 and CEA in chordoma might not be as common as what has been previously reported. The results also suggest that parachordoma might not be easily distinguished immunohistochemically from axial chordoma (and therefore also from so-called chordoma periphericum).

Myoepithelioma of the soft tissue of the head and neck: a case report and review of the literature

BACKGROUND

Extraglandular myoepitheliomas are neoplasms that seldom occur in the soft tissue of the head and neck region. Misdiagnosis of these neoplasms as more aggressive tumors can lead to unnecessary treatment.

METHODS

We describe a myoepithelioma of cervical soft tissue. The histopathology of the tumor, its immunophenotype, its differential diagnosis, and a review of the literature are presented.

RESULTS

Histopathologically, the tumor was composed of epithelioid cells with eosinophilic cytoplasm and eccentric nuclei arranged in cords and files. On immunohistochemical analysis, the cells expressed cytokeratin 14, calponin, glial fibrillary acid protein, and p63 and showed focal positivity for S-100 protein. Together, these markers identified the cells as myoepithelial type. A literature review identified only five cases of myoepithelioma in the soft tissue of the head and neck region in which detailed clinical information was provided.

CONCLUSIONS

Myoepitheliomas can have cells with variable morphology arranged in different histologic patterns. Immunohistochemical analysis is crucial for unequivocal diagnosis when myoepitheliomas occur in extraglandular locations.

Myoepithelial tumors of soft tissue: a clinicopathologic and immunohistochemical study of 101 cases with evaluation of prognostic parameters

Myoepitheliomas and mixed tumors were only recently recognized to occur primarily in soft tissue, and only small case numbers have been described. To characterize these tumors further and to evaluate prognostic parameters, 101 myoepithelial tumors of soft tissue were retrieved from the authors' consult files. Hematoxylin and eosin sections were reexamined, immunohistochemistry was performed, and clinical details were obtained from referring physicians. Fifty-three patients were male and 48 female (mean age 38 years; range 3-83 years). Tumor size ranged from 0.7 to 20 cm (mean 4.7 cm). Most tumors arose in the extremities and limb girdles: 41 in the lower limbs, 35 in the upper limbs, 15 in the head and neck, and 10 in the trunk. Fifty-four tumors were situated in subcutis and 37 in deep soft tissue (depth unstated in 10). Most cases were grossly well circumscribed; 43 showed microscopically infiltrative margins. Histologically, most tumors were lobulated, composed of cords or nests of epithelioid, ovoid, or spindled cells with a variably reticular architecture and a chondromyxoid or collagenous/hyalinized stroma. Eight cases showed a predominantly solid proliferation of spindled or plasmacytoid cells; 17 demonstrated ductular differentiation (mixed tumors). Cartilage was present in 6 cases, 6 contained bone, and 4 others contained both. Mitoses ranged from 0 to 68 per 10 high power fields (mean 4.7 per 10 high power fields). Tumors with benign cytomorphology or mild cytologic atypia (low-grade) were classified as myoepithelioma or mixed tumor, whereas tumors with moderate to severe atypia (high-grade) were classified as myoepithelial carcinoma (epithelioid or spindled cells with vesicular or coarse chromatin, prominent, often large nucleoli, or nuclear pleomorphism) or malignant mixed tumor (cytologically malignant cartilage or bone). Sixty-one cases were myoepitheliomas or mixed tumors, and 40 were myoepithelial carcinomas or malignant mixed tumors. By immunohistochemistry, all cases with available material were reactive for epithelial markers (keratins and/or epithelial membrane antigen): 90 of 97 (93%) expressed keratins (most often AE1/AE3 or PAN-K), 84 of 97 (87%) S-100 protein, 44 of 51 (86%) calponin, 52 of 83 (63%) epithelial membrane antigen, 40 of 87 (46%) glial fibrillary acidic protein, 27 of 75 (36%) smooth muscle actin, 15 of 66 (23%) p63, and 7 of 51 (14%) desmin. Follow-up was available for 64 patients. Among 33 cases with benign or low-grade cytology (mean follow-up 36 months; range 4-168 months), 6 recurred locally (18%) and none metastasized. No clinical or histologic features correlated with recurrence. Among 31 cytologically malignant cases (mean follow-up 50 months; range 4-252 months), 13 recurred locally (42%) and 10 metastasized (32%); so far, 4 patients have died of metastatic tumor. This study expands the spectrum of myoepithelial tumors of soft tissue to include myoepithelial carcinomas and malignant mixed tumors, which pursue an aggressive clinical course. Although the majority of morphologically benign or low-grade myoepithelial neoplasms of soft tissue behave in a benign fashion, there is an approximate 20% risk for local recurrence.

Parachordoma with multiple metastases

We present a very rare case of parachordoma with local aggressiveness and widespread metastases. A 68-year-old male presented with a mass in his left calf. The lesion was depicted as a poorly marginated mass with inhomogeneous signal intensity on magnetic resonance imaging. The tumor invaded surrounding muscles, neurovascular bundles, and bones. Widespread metastasis to lung, bone, and skin developed after amputation surgery. The histologic features of primary and metastatic lesions were the same and consistent with parachordoma.

Chordoma periphericum: a case report

The authors describe a tumor that had the histologic and ultrastructural features and immunohistochemical profile of an axial chordoma, but arose in the distal ulna. A skeletal survey failed to show any other site of involvement. The tumor was resected, and the patient remains free of disease 2 1/2 years later. Rare tumors with the histologic features of chordoma have been reported in appendicular locations. Chordoma periphericum, a tumor that has the potential to metastasize, needs to be distinguished from parachordoma because no classic parachordoma has been reported to disseminate.

Parachordoma of the tibia: report of a rare case

We report a case of recurrent parachordoma of the left anterior tibial region in a 64-year-old male patient. The tumor was a periosteal tender mass, and, histologically, displayed vague nodules of spindle to rounded eosinophilic cells embedded in a myxoid matrix. Large vacuolated (physalphorouslike) cells were noted as in sacrococcygeal chordoma. This tumor should be differentiated from myxoid chondrosarcoma, myxoid liposarcoma, chondromyxoid fibroma, and metastatic chordoma. The presence of physaliphorous cells in the tumor with positive immunoreactions caused by cytokeratin rules out the diagnosis of another myxoid tumor. The differential diagnosis from metastatic chordoma is basically made by clinicians. Even though parachordoma is usually regarded as a benign soft tissue neoplasm, two recurrences occurred in our case. Since the reported cases, including ours, have diverse clinical courses, it is essential to follow-up the patient carefully.

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.

Chest wall parachordoma

A 21-year-old woman with a painful chest wall mass was found to have a parachordoma (PC). The tumor arose from the fifth intercostal space. A wide chest wall resection including the tumor and a 2.5 cm free margin and the subsequent reconstruction with a Gore-Tex soft tissue patch covered with a latissimus dorsi rotational flap was performed. To our knowledge, chest wall parachordoma has not been previously reported in the medical literature.

Parachordoma is immunohistochemically and cytogenetically distinct from axial chordoma and extraskeletal myxoid chondrosarcoma

Parachordoma is a rare soft-tissue tumor resembling extraskeletal myxoid chondrosarcoma and chordoma. Because fewer than 30 cases have been reported and precisely characterized, we studied the clinicopathologic features of seven new cases, comparing the immunohistochemical (six cases) and cytogenetic (one case) profiles with 15 cases of chordoma and six cases of extraskeletal myxoid chondrosarcoma. Patients with these tumors ranged in age from 7 to 62 years (mean, 35 years) and included four women and three men. The tumors presented as subfascial masses of the thigh (two cases), arm (three cases), chest wall (one cases), and buttocks (one case). In six of seven cases, there was neither recurrence nor metastasis within the follow-up, which ranged from 4 months to 7 years. The tumors were composed of vague nodules of large, rounded eosinophilic cells embedded in a matrix that varied from myxoid to densely hyaline, and the latter areas occasionally resembled primitive cartilage. Transitions between the large eosinophilic cells and smaller rounded and shorter spindled ones were often noted. Multivacuolated (physaliferouslike) cells were noted in all cases but were usually few in number. The matrix stained with Alcian blue (pH 2.5), and this staining was abolished with hyaluronidase predigestion. Immunohistochemistry for a variety of cytokeratins (CKs) (8/18, 1/10, 7, and 20), epithelial membrane antigen (EMA), S-100 protein, vimentin CD34, type IV collagen, smooth muscle actin, smooth muscle myosin heavy chain, calponin, and glial fibrillary acid protein was performed. All parachordomas strongly expressed CK 8/18, but not the other cytokeratins. Additionally, they expressed EMA (five of six). S-100 protein (six of six), and vimentin (six of six) and had a linear pattern of type IV collagen immunoreactivity around nests of cells (four of five). Calponin was noted in one case, but no cases expressed smooth muscle actin, smooth muscle myosin heavy chain, or glial fibrillary acid protein. In contrast, chordoma expressed CK 8/18 (15 of 15) and CK 1/10 (14 of 15), whereas extraskeletal myxoid chondrosarcoma consistently lacked CK. Although chordoma and extraskeletal myxoid chondrosarcoma showed considerable overlap with parachordoma, with respect to EMA and S-100 protein, they infrequently displayed type IV collagen, as was seen in parachordoma. One case of parachordoma studied cytogenetically disclosed trisomy 15, and monosomies of 1, 16, and 17 in contrast to the t(9;22) reported in extraskeletal myxoid chondrosarcoma and the monosomies of 3, 4, 10, and 13 seen in chordoma. We conclude that the immunohistochemical and cytogenetic profile distinguishes parachordoma from extraskeletal myxoid chondrosarcoma and chordoma. Lack of myoepithelial markers, furthermore, suggests parachordoma is not a deeply situated adnexal tumor. Because of these differences, parachordoma is best regarded as a distinct lesion without a clear relationship to other well-characterized tumors.

Skeletal and extraskeletal myxoid chondrosarcoma: a comparative clinicopathologic, ultrastructural, and molecular study

BACKGROUND

Skeletal myxoid chondrosarcoma (SMC) is considered to be either a typical chondrosarcoma with prominent myxoid alterations or an altogether unique malignant cartilage tumor. Extraskeletal myxoid chondrosarcoma (EMC) is a relatively rare but well-recognized neoplasm. It was initially thought to be a low grade sarcoma of cartilage derivation and was recently found, in most cases, to contain a reciprocal t(9;22), resulting in a fusion of the EWS and CHN genes. Are SMC and EMC the same entity arising in two different locations, or are they two separate entities? To the authors' knowledge, this study represents the first systematic attempt to answer this question.

METHODS

Forty consecutive cases of EMC (20 cases) and SMC (20 cases) were compared by light and electron microscopy, immunohistochemistry, and molecular analysis. The mean clinical follow-up for both groups was 55 months. Histologic criteria for SMC consisted of 95% myxoid matrix, with only minimal hyaline cartilage formation.

RESULTS

The gender distribution was identical in both groups (13 males and 7 females). The mean age was 55 years for EMC patients and 45 years for SMC patients. The EMC tumors were predominantly located in the deep soft tissues of the lower extremity (60%) and buttock (20%), and the mean tumor size was 13 cm. SMC was most commonly located in the bones around the hip joint (pelvis 35%; proximal femur 20%) and shoulder (20%); the mean size was 9 cm. Histologic grade in the EMC group correlated with survival (82% of the high grade tumors metastasized). Electron microscopy performed in 8 EMC cases revealed intracisternal microtubules in 3 cases and prominent mitochondria in 5, whereas in 5 SMC cases it revealed only inconspicuous organelles. Molecular analysis for the EWS-CHN fusion RNA resulting from the t(9;22) was performed in 15 cases (9 EMC and 6 SMC) and was detected in 7 of 9 EMC cases and 0 of 6 SMC cases. In one case, the molecular structure of the EWS-CHN fusion RNA was novel. The probability of metastasis was significantly higher (P=0.004) for the EMC group than for the SMC group.

CONCLUSIONS

Although similar light microscopic features are noted in EMC and SMC, fundamental differences are noted at the ultrastructural and molecular levels, suggesting that EMC and SMC represent two distinct entities in the chondrosarcoma family of tumors.