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Keywords:

  • fine-needle aspiration biopsy;
  • FISH;
  • extraskeletal myxoid chondrosarcoma;
  • myxoid soft tissue tumors

Abstract

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. REFERENCES

BACKGROUND.

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft-tissue sarcoma rarely subjected to cytologic analysis. With the exception of a few small series, the cytology literature of EMC is largely limited to single-case reports. The purpose was to evaluate the cytomorphology of 8 EMC cases as obtained by imprint/scrape cytology and fine-needle aspiration (FNA) biopsy, to review the literature, and to demonstrate the utility of cytogenetic analysis in the diagnosis of EMC.

METHODS.

The cytology files were reviewed for all soft-tissue lesions signed out as chondrosarcoma, myxoid sarcoma, and EMC, and the tissue files for any cases of EMC that had corresponding cytopathology. FNA was performed using a standard technique. Scrape preparations were performed from tissue sent fresh to the laboratory for either frozen section or for special studies such as electron microscopy or tissue banking.

RESULTS.

Eight cases of EMC were retrieved from 4 men and 3 women (median age = 62 years). One patient had 2 separate cytologic specimens 4.5 years apart. All patients had subsequent tissue confirmation of the diagnosis of EMC. Five individuals presented as new patients, and 2 had a prior diagnosis of EMC. Sites included 4 masses from the foot/ankle, 2 from the calf, 1 wrist mass, and 1 buttock mass. Five patients were diagnosed from FNA biopsy, whereas 3 were diagnosed using scrape slides. Five cases were correctly and categorically diagnosed by the cytologic method as EMC, 1 as chondrosarcoma favor EMC, 1 as sarcoma favor EMC, and 1 as myxoid spindle/epithelial neoplasm. Cytologic features ranged from hypocellular to highly cellular smears composed primarily of rounded cells set in an abundant myxoid stroma that varied from opaque to semitransparent and lacked vascularity or necrosis. Smears showed cells in short, sometimes anastomosing cords, but also as single cells and nondescript cell clusters. Cells displayed a monotonous uniformity in nuclear diameter and cell size. Bland nuclei with evenly dispersed chromatin displayed variably sized nucleoli, and a moderate amount of infrequently vacuolated cytoplasm. Tissue fragments of variable size were found in 5 of 5 FNA cell blocks. Fluorescence in situ hybridization (FISH) analysis using the EWSR1 probe showed a positive 22q12 translocation in 2 of 3 FNA cases that were tested. One case with negative FISH results on the cytologic preparation showed a positive translocation using the same technique in the subsequent resection specimen.

CONCLUSIONS.

A confident cytologic diagnosis of EMC depends on the presence of a uniform, round to oval cell population often arranged in cords and set in an abundant myxoid/chondromyxoid background and arising in the appropriate clinical context. If positive, FISH testing (of paraffin cell blocks or cytospin preparations) is confirmatory when coupled with this cytomorphology. Cancer (Cancer Cytopathol) 2007. © 2007 American Cancer Society.

Since its reemergence in the latter half of the 20th century, cytopathology and, particularly, fine-needle aspiration (FNA) biopsy-performed cytopathology has been increasingly applied to a variety of internal and external anatomic sites in North American medical centers. Nonetheless, among the least favored of locations to apply the FNA technique, and to use cytopathology in general, is to a mass lesion arising from the somatic soft tissues. This is particularly so if a clinical diagnosis of sarcoma is entertained.

In our bone and soft tissue clinic, however, FNA biopsy has become an integral component in the diagnostic workup of all types of suspected soft-tissue lesions. A review of our files revealed a set of cases of extraskeletal myxoid chondrosarcoma (EMC). Because EMC is primarily the subject of case reports in the cytology literature, we wished to report our experience, to review the literature regarding the cytopathology of this neoplasm, and to compare EMC to a set of other myxoid soft-tissue tumors. We also wish to demonstrate that a definitive diagnosis of EMC is possible using the FNA technique when it is combined with ancillary cytogenetic testing.

MATERIALS AND METHODS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. REFERENCES

Case Selection

We reviewed our cytology files for all cases signed out as chondrosarcoma, myxoid sarcoma, and EMC, and our surgical pathology case files for any cases of EMC that had corresponding cytopathology. In addition, fine-needle aspirates from a control set of other myxoid soft-tissue tumors that potentially may simulate EMC were retrieved for morphologic comparison.

Technique

Percutaneous FNA biopsy was performed without local anesthesia by a single pathologist in all 5 cases using a standard technique with 21- or 22-gauge needles. Three to 4 passes were made into the lesion and each pass was rinsed in a balanced salt solution after expelling cell material onto glass slides for the creation of conventionally made direct smears. Imprint and scrape slides were made by touching or scraping the cut surface of fresh tissue (at the time of frozen section examination) to create conventional smears that were stained and interpreted along with the tissue section. Slides were stained using both Papanicolaou (P) and Romanowsky (R) stains. All slides were air-dried; those that were P-stained underwent rehydration and alcohol fixation before staining. Formalin-fixed, paraffin-embedded cell block sections were attempted from each FNA case and stained with hematoxylin and eosin. No liquid-based slides or cytospin preparations were made.

Fluorescence in situ hybridization (FISH) testing was performed using a commercially available LSI EWSR1 dual color break apart probe set (Vysis, Downers Grove, Ill). This probe is used to examine for a translocation involving the EWSR1 gene on chromosome 22q12. An abnormal cell with a translocation will reveal 1 pair of separate or ‘split’ signals rather that 2 fused signals as would occur in a normal cell. Split signals in greater that 20% of cells were considered a positive result for EWSR1 translocation.

Immunohistology was performed from the cell block material using antibodies to EMA, vimentin NSE, synaptophysin, muscle specific actin, desmin, S-100, CD45, and cytokeratin AE 1/3.

RESULTS

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. REFERENCES

We recovered 8 cytologic cases of EMC from 7 patients (M:F = 4:3), and all were histologically confirmed by subsequent surgical resection. Five cases were diagnosed using FNA biopsy alone (Table 1), whereas 3 cases were diagnosed using scrape cytology in concert with frozen section tissue analysis (Table 2). Patients ranged from 42 to 82 (median age = 62) years. Five individuals presented without a prior diagnosis. One individual had a prior diagnosis of EMC made 1.5 years earlier (Case 8). The other individual with recurrent EMC had the original tumor removed 20 years before her first recurrence (Case 6), and 4.5 years before her second recurrence (Case 1). All recurrent EMC cases originated in the same location as did the original tumor.

Table 1. FNA of Extraskeletal Myxoid Chondrosarcoma
Case No.Age, y/SexP/RLocationProcedure/Tumor Size (cm)Cytologic DiagnosisFISH TestingTissue Diagnosis
  1. P indicates primary; R, recurrent; FNA, fine-needle aspiration biopsy; pos, positive; neg, negative; nd, not done; EMC, extraskeletal myxoid chondrosarcoma; FISH, fluorescence in situ hybridization.

161/FRMedial left footFNA/1.5EMCposEMC
242/MPLeft lateral calfFNA/10EMCndEMC
368/MPButtockFNA/2EMCndEMC
482/MPL footFNA/4Sarcoma, favor EMCnegEMC
566/FPR calfFNA/11EMCposEMC
Table 2. Scrape Cytology of Extraskeletal Myxoid Chondrosarcoma
Case No.Age, y/SexP/RLocationProcedure/Tumor Size (cm)Cytologic DiagnosisFISH TestingTissue Diagnosis
  1. P indicates primary; R, recurrent; nd, not done; EMC, extraskeletal myxoid chondrosarcoma; FISH, fluorescence in situ hybridization.

657/FRLeft ankleScrape/1.5Myxoid spindle cell tumorndEMC
758/FPLeft footScrape/2EMCndEMC
865/MRRight wristScrape/1.2Chondrosarcoma, favor EMCndEMC

All masses arose from soft tissue without underlying bone involvement and included 4 from the foot/ankle, 2 from the calf, 1 wrist mass, and 1 buttock mass. For patients who underwent FNA biopsy, the mass ranged from 1.5 to 11 cm in greatest dimension. Four of 5 patients who had an FNA biopsy performed presented with no known diagnosis. FNA biopsies were performed several days to a few weeks before definitive surgical resection. Scrape cytology was performed on fresh tissue from 2 recurrent and 1 previously undiagnosed EMC simultaneous with the surgeon's request for frozen section analysis. Of the 5 FNA cases, 4 were categorically diagnosed as EMC; this included the single recurrent EMC and 3 of the 4 primary EMCs. Three of these were subjected to FISH analysis from the cell block material using the EWSR1 dual color breakapart probe. Two of the 3 showed positive FISH results allowing for an unambiguous cytologic interpretation of EMC. Because a single FNA case had negative FISH results a less definitive interpretation of ‘Sarcoma favor EMC’ was made. Yet repeat FISH testing on the resection specimen showed evidence of a positive translocation (Case 4). Scrape cytologic smears were examined in concert with cryostat frozen tissue analysis. One case not originally examined by the authors was diagnosed as a myxoid/spindle cell tumor, whereas the 2 scrape cytology cases seen by 1 of the authors were diagnosed correctly as EMC and as ‘chondrosarcoma favor EMC.’

Cytologic features were similar in all cases. All contained a background myxoid/chondromyxoid stroma that tended to exist in a larger amount in aspirate slides than in the scrape slides. This stroma was most obvious in R-stained slides where it appeared as a dark magenta, but was also visible (however muted) in P-stained smears. In most cases it was spread as a film of variable thickness on the glass slide, but also existed in discrete inspissated pieces that often had a frayed, fibrillar, or even a smooth edge (Fig. 1). Cellularity ranged from very high to some smears having large hypocellular zones containing only stroma. As expected from its histopathology, smears of EMC were composed primarily of 1 cell type that had an epithelioid/rounded shape; a minor population of spindle-shaped cells was seen in 2 cases. Epithelioid cells were arranged as single cells, as cells in clusters with and without concomitant stroma, and as cells in linear trabecular shaped cords. These trabeculae could be 1 or several cells thick (Fig. 2). This latter feature was obvious in all but 2 cases and was most pronounced in slides made from FNA biopsy. In some smears cell clusters had rounded (lobular or ball-like) discrete sharp borders, whereas in others cells loosely trailed away from the cluster center as single cells (Fig. 3). Cell monotony was the rule among all cases, with individual cells having rounded single nuclei with evenly dispersed chromatin, a moderate amount of cytoplasm, and nucleoli that ranged from being barely discernible to large (Fig. 4). One case had nuclei with discernible nuclear grooves, and infrequently an intranuclear inclusion could be found among these cases. Cytoplasmic vacuoles were rare except for 2 FNA cases where they were obvious, and occurred in a perinuclear fashion creating an almost ‘lacunar’ appearance (Fig. 5). Smear background was devoid of necrosis, inflammation, and obvious vascularity in all cases.

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Figure 1. (A) An acellular thin film of semitransparent metachromatic staining myxoid stroma occupies nearly the entire field. A small cell cluster is at the upper right. Romanowsky stain. (B) An inspissated block of opaque myxoid material is surrounded by thinner slightly transparent stroma. Although cells are embedded within the inspissated fragment it is too opaque to see them at this low magnification. Romanowsky stain.

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Figure 2. (A) Cells of uniform size and shape are aligned almost like ‘beads on an invisible string’ set in a myxoid background. Romanowsky stain. (B) Interconnecting epithelioid cells are in 2 to 3-cell thick trabeculae mimicking plates of hepatocytes. Note the muted coloration of the background stroma with this stain. Papanicolaou stain.

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Figure 3. (A) Two compact cell fragments display smooth undulating and lobular outer contours. Papanicolaou stain. (B) This nonspecific pattern shows cells at the periphery of intensely cellular clusters ‘dropping away’ as individuals forms. Papanicolaou stain.

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Figure 4. (A) Rounded cells have evenly dispersed chromatin and obvious single nucleoli. A moderate amount of granular cytoplasm is seen. Romanowsky stain. (B) Note that the nuclei in this case have barely discernible nucleoli in contrast to image 4A. The cell in the center contains an intranuclear cytoplasmic pseudoinclusion. Papanicolaou stain.

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Figure 5. A circumferential perinuclear halo combined with a thickened discrete cell membrane produces a ‘lacunar effect’ to these cells. Papanicolaou stain.

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Cells blocks were made from all 5 aspirate cases. Although tissue fragments were present in all (some in miniscule amounts), immunohistology was performed from the cell block on only 2 cases (Cases 4 and 5). Positive results included staining of EMC fragments with vimentin (2 of 2), EMA (1 of 2), NSE (1 of 1), and synaptophysin (dot-like in 2 of 2). Negative results were cytokeratin AE 1/3 (0 of 2), muscle specific actin (0 of 2), S-100 (0 of 2), desmin (0 of 1), and CD45 (0 of 1).

EMC cases were compared with conventional FNA smears of 23 other myxoid soft-tissue tumors. These included myxoid liposarcoma (LPS) (6 cases), low-grade myxofibrosarcoma (MFS) (5 cases), myxoma (5 cases), myxoid leiomyosarcoma (LMS) (1 case), low-grade fibromyxoid sarcoma (LGFS) (2 cases), chordoma (3 cases), and ossifying fibromyxoid tumor (OFT) (1 case). Smears from each of these lesions showed a variety of morphologic features that did not exist in EMC slides. These included branching vascularity and nonlipogenic spindle cells (myxoid LPS), nuclear pleomorphism and atypia (low-grade MFS, chordoma, and myxoid LMS), binucleated and multinucleated cells (chordoma), markedly hypocellular smears containing almost no cells except for muciphages and bland spindle cells (myxoma), and a pure spindle cell population (LGFS). In addition, none of these other myxoid lesions contained cell in cords and anastomosing trabeculae as seen in EMC, and none contained perinuclear halos. The single case of OFT was similar to EMC, but also lacked these latter 2 features.

DISCUSSION

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. REFERENCES

EMC is a rare soft-tissue tumor that most often occurs in the extremities of middle-age adults (median age 50 years) with a male-to-female ratio of 2:1.1 Rare cases have been reported in other anatomic locations, and even in children. The diagnostic term EMC was coined by Enzinger and Siraki2 more than 30 years ago, and is the preferred designation by the WHO.1 Nearly all publications regarding EMC give credit for the initial description of this neoplasm to Stout and Verner.3 Nonetheless, an earlier publication of this neoplasm with identical histomorphology by Stewart4 was termed “chordoid sarcoma” because of its histologic resemblance to chordoma. Recent reports indicate that Stewart's term is probably more correct. Mounting evidence demonstrates that there is not a great deal that is convincingly ‘chondrosarcomatous’ about EMC. Only a small percentage of EMC cases happen to be S-100-positive (a nearly universal stain of conventional skeletal chondrosarcoma), a high percentage show evidence of neuroendocrine differentiation, and investigation of the matrix of EMC shows an absence of any of the collagen subtypes specific for chondrocyte differentiation in the majority of cases.5

After excluding cases of skeletal chondrosarcoma involving soft tissue, we found 29 cases describing the cytopathology of EMC in the English literature (Table 3).6–24 Series containing 5 cases,21 4 cases,23 3 cases,16 and 2 cases24 have been reported. All remaining examples are single-case reports. These publications illustrate and describe features very similar to our series of 8 cases of EMC. All mention a myxoid stroma of variable thickness, and most describe cells arranged, at least in part, into linear arrays/cords—a point emphasized in the 5 cases of Kilpatrick et al21 and often described as lace-like by many of these authors. This pattern is illustrated in Figures 2 and 3. Some reports describe cells in primitive lacunar formations,10 with nuclear grooves,10, 16 intranuclear inclusions,18 and a rare report describes the presence of “prominent capillaries.”14 One case described the presence of 3 cells types with cartilaginous differentiation.20 No other reports described this variety of cell types, and we observed no frank cartilaginous change in any of our examples.

Table 3. Reported Cases of Extraskeletal Myxoid Chondrosarcoma by FNA
ReferenceYear of publicationNo. of casesAge, y/SexAnatomic siteMetastatic, Primary, or Recurrent
Domanski et al.2003149/FLeft thigh and left groinPrimary
Gaudier et al.2003139/MPeriumbilical areaPrimary
Layfield et al.20031unknownunknownUnknown
Rao et al.2002130/FLeft breast-chest wallPrimary
Wadhwa et al.2000150/MRight calfPrimary
Gonidi et al.1997182/FThighPrimary
Tunc et al.1996160/MInguinal regionPrimary
Mukhopadhyay et al.2003174/MChest wallPrimary
Jones et al.1995187/MLeft scapulaPrimary
Gordon et al.1994172/MRight axillaPrimary
Niemann et al.1994345/MRight groinMetastatic
  87/MLeft forearmPrimary
  61/MRight buttockPrimary
Orndal et al.1991173/MUpper armPrimary
Insabato et al.1990165/MAnterior right thighPrimary
Gonzalez-Campora1990138/MThighPrimary
Tsang et al.1985170/MAbdominal massMetastatic
Kilpatrick et al.2000549/MLeft armPrimary
  47/MLeft thighPrimary
  65/FRight thighPrimary
  71/FRight thighPrimary
  32/MLeft anklePrimary
Etit et al.2004143/MGluteal regionPrimary
Bjerkehagen et al.1999471/MRight thighPrimary
  47/MLeft thighPrimary
  60/MLeft lower armRecurrent
  47/MRight thighPrimary
Kindblom1986228/MThighPrimary
  58/FThighPrimary

EMC has no distinctive immunohistochemical profile. Whereas nearly all examples are vimentin-positive, S-100 and EMA staining is reported in as few as 20% of cases in some series, and is often focal when present. A large percentage of EMC cases, however, show reactivity for neuroendocrine markers NSE and synaptophysin.6, 25 Synaptophysin staining was seen in the cell blocks from both of our cases submitted for immunostaining. It was found in almost 90% of 15 cases studied by Goh et al,25 with over two thirds showing strong, diffuse staining. All 11 of their cases examined ultrastructurally revealed dense-core neurosecretory granules of variable density. Evidence of neural-neuroendocrine differentiation in EMC has also been reported using gene expression profiling.26

Histologic grading in the vast majority of EMC cases conforms to a low-intermediate grade. All 8 of our cases were graded as such. However, a small number of so-called high-grade EMC have been described. These are characterized by tumors with greater cellularity, increased mitoses, and necrosis. The cell morphology is 1 of large epithelioid (sometimes rhabdoid) cells having vesicular nuclei, and very large nucleoli as well as foci with spindled sarcomatous transformation.27 We are not aware of any reports illustrating the cytopathology of this high-grade variant.

EMC is associated with several chromosomal translocations including t(9;22)(q22;q12), t(9;17)(q22;q11), t(9;15)(q22;q21), and trisomies 7, 8, 12, 18, 19, and 22.28 The t(9;22)(q22;q12) is the most common translocation fusing the EWSR1 gene on 22q12 to the TEC gene located on 9q22, resulting in a translocation that appears specific for EMC. Fortuitously, such a translocation can be detected with a commercially available EWRS1 probe using the FISH technique. It should be remembered, however, that the EWSR1 (22q12) probe used in FISH analysis is not specific for EMC because the break-apart nature of this technique does not allow for identification of the specific translocation partner—in this case, the TEC gene on chromosome 9. Thus, a purely positive FISH result using an EWSR1 probe is not diagnostic; the result must be interpreted in the context of its cytopathology. Other neoplasms harboring a translocation involving chromosome 22 include Ewing sarcoma t(11;22)(q24;q12), desmoplastic small round cell tumor t(11;22)(p13;q12), clear cell sarcoma of soft parts t(12;22)(q13;q12), and uncommonly myxoid liposarcoma t(12;22)(q13;q12).29 Nonetheless, when the aforementioned cytologic morphology is coupled with a positive FISH result for EWSR1, it is our belief that an unequivocal diagnosis of EMC can be rendered (as occurred in 2 of our cases). This is because these other soft-tissue neoplasms do not display any of the cytopathologic features of EMC as detailed in this and in prior reports. Bjerkehagen et al23 also performed cytogenetic analysis using the cytologic specimen to assist with the diagnosis of EMC. Two of their FNA cases were subjected to conventional karyotyping, not FISH testing, to document a translocation involving chromosome 22.

The abundance of myxoid stroma in all EMC cases forces one to consider a differential diagnosis of myxoid soft-tissue neoplasms.30 In our examination of 23 other myxoid tumors in concert with our 8 EMC cases, we found the EMC cases lacked the vascularity of myxoid LPS, the nuclear atypia and pleomorphism of myxofibrosarcoma, chordoma, and myxoid LMS, the near absence of cellularity of myxoma, the binucleation of chordoma, and the spindle cell population of low-grade fibromyxoid sarcoma. Moreover, the cord-like arrangement seen in most EMC slides was lacking in these other neoplasms. A soft-tissue tumor that may be extremely difficult to distinguish from EMC using morphology alone is soft-tissue myoepithelioma/parachordoma. However, we have not encountered any cytologic examples of this neoplasm, and its cytopathology has only rarely been described.31 Even so, ancillary immunostaining should differentiate between these 2 neoplasms, as the latter is routinely cytokeratin-positive, whereas EMC is not.

Our series is too small for meaningful statistical analysis. However, we demonstrate that a cytopathologic diagnosis of EMC is possible in a high percentage of cases. Our report also emphasizes the practical diagnostic utility of cytogenetic testing for a select group of soft-tissue tumors as procured by FNA biopsy.

REFERENCES

  1. Top of page
  2. Abstract
  3. MATERIALS AND METHODS
  4. RESULTS
  5. DISCUSSION
  6. REFERENCES