Extraskeletal myxoid chondrosarcoma: multimodal diagnosis and identification of a new cytogenetic subgroup characterized by t(9;17)(q22;q11)

Abstract

Extraskeletal myxoid chondrosarcoma is a rare malignant soft tissue tumour that can be difficult to diagnose correctly, especially preoperatively. We describe four cases of extraskeletal myxoid chondrosarcoma of the extremities diagnosed by a multimodal approach. The cytological examination of fine-needle aspirates showed small and round, mildly pleomorphic cells lying in sheets and cords, but also dispersed within a myxoid and metachromatic intercellular substance. Histological, electron microscopic and immunocytochemical examination also yielded findings compatible with the diagnosis of extraskeletal myxoid chondrosarcoma. Cytogenetic analysis demonstrated a t(9;22)(q22;q12) in two tumours and a t(9;17)(q22;q11) in the third and fourth. The translocation t(9;22)(q22;q12) has been described repeatedly in extraskeletal myxoid chondrosarcoma but never in other tumours; hence, the detection of this pathognomonic chromosome abnormality in short-term cultured cells from fine-needle aspirates verified the diagnosis in two of the cases. The t(9;17)(q22;q11) found in the last two cases probably represents a new cytogenetic subgroup of extraskeletal myxoid chondrosarcoma as it, too, is unknown in other contexts. The multimodal approach taken in these four cases enabled a definite diagnosis of a rare malignant tumour whose cytological and histological features alone are usually not sufficiently distinct to rule out other differential diagnostic possibilities.

Cytopathology of extraskeletal myxoid chondrosarcoma

“…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][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] Series containing 5 cases, 21 4 cases, 23 3 cases, 16 and 2 cases 24 have been reported. All remaining examples are single-case reports.…”

Fusion of the RBP56 and CHN genes in extraskeletal myxoid chondrosarcomas with translocation t(9;17)(q22;q11)

“…Recently, however, another translocation not previously described, t(9;17)(q22;q11) (Figure 1), was reported in two EMC, thus identifying a second cytogenetic subgroup of this tumour type (Bjerkehagen et al, 1999). The 9;22-translocation fuses the EWS gene from chromosome 22 with the CHN gene (also named TEC, NOR-1 or MINOR), which encodes an orphan nuclear receptor, from 9q22 (Labelle et al, 1995;Clark et al, 1996).…”

Extraskeletal myxoid chondrosarcoma of the thigh with a t(9;17) translocation

“…Of the 50 cases, t(9;17)(q22;q11) was observed in nine cases (18%). t(9;17) (q22;q11) results in the fusion of TAF15, located at 17q11, to NR4A3, located at 9q22, to form the abnormal fusion gene TAF15/NR4A3 (15,19,27). t(9;22)(q22;q12) and t(9;17)(q22;q11) have not been found in any other tumors.…”

“…As cartilaginous areas are not common despite the name 'EMC', making a diagnosis based solely on histopathological findings is often difficult. At present, the number of reported cytogenetic studies of EMC remains small due to the rarity of the tumor (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). We report an additional case of EMC and review the literature on cytogenetic studies.…”