comparative genomic hybridisation (aCGH) analysis
was carried out using the OGT CytoSure
oligoarray set (Oxford Gene Technology, Oxford, UK),
containing 180k DNA oligonucleotides with a mini-
mum resolution of 200 kb. Microarray hybridisation
and copy number variant (CNV) analysis were per-
formed according to the manufacturer’s instructions.
All genome coordinates were according to NCBI
human genome build 37 (hg19, February 2009).
aCGH analysis revealed only a few copy number
aberrations, as follows: arr[GRCh37] 2q24.1q31.1
26335543)x1 and 13q12.2q34(27940855-1150
93155)x1 (Figure 3C). Of note, there was no overlap
of these numerical changes with the genomic copy
number alterations reported recently in similar
tumours by Bale et al.
Thus, these might be sec-
ondary genetic alterations of as-yet unknown biologi-
Within the group of mesenchymal tumours with
EWSR1–CREB gene family fusions, this newly
described entity, of which we document the ninth
case, shows histological overlap with the primary pul-
monary myxoid sarcoma and myxoid angiomatoid
ﬁbrous histiocytoma. However, the ﬁrst tumour pre-
sents as endobronchial lesions in adult patients and,
for the latter, a ﬁbrous pseudocapsule, peritumoral
lymphoplasmacytic inﬁltrates and blood-ﬁlled cystic
spaces were lacking. There are two other myxoid
mesenchymal tumours with EWSR1 involvement:
extraskeletal myxoid chondrosarcoma (EMC) and
myoepithelial tumours. EMC occurs typically in the
deep soft tissue of the limb in middle-aged adults. and
in the vast majority of cases NR4A3 is the transloca-
tion partner. Myoepitheliomas also show histological
overlap, but combine expression of keratin and/or
EMA with S100 protein and/or GFAP. Moreover, var-
ious translocation partners have been described so
far: POU5F1, PBX1, PBX3, ZNF444 and KLF17.
Only one myoepithelial tumour in the pelvis of an
adult was reported to have a EWSR1–ATF1 fusion,
but the immunophenotype was typical for myoepithe-
Within the cranium, only three primary
myoepitheliomas have been described, with typical
expression of keratin, S100 protein and GFAP, but no
documented EWSR1 rearrangement.
Our case con-
ﬁrms the observation of recurrent genetic alteration
involving EWSR1 gene in myxoid mesenchymal
intracranial tumours by Kao et al. (2017) and Bale
et al. (2017), the second case carrying the
EWSR1–ATF1 fusion. Interestingly, amianthoid-like
ﬁbres are lacking in the two cases with the EWSR1–
ATF1 fusion, but are reported in the six cases with
the other fusions. The potential signiﬁcance of this is
not clear. A combined approach using immunohisto-
chemistry and molecular analysis is recommended to
separate this rare entity from its mimics. The poten-
tial relation with myxoid angiomatoid ﬁbrous histio-
cytoma awaits further study.
Frank Van Calenbergh
Departments of Pathology,
Human Genetics, KU Leuven
and University Hospitals Leuven, Leuven, Belgium
1. Thway K, Fisher C. Tumors with EWSR1–CREB1 and EWSR1–
ATF1 fusions: the current status. Am. J. Surg. Pathol. 2012; 36;
2. Kao YC, Sung YS, Zhang L et al. EWSR1 fusions with CREB
family transcription factors deﬁne a novel myxoid mesenchymal
tumor with predilection for intracranial location. Am. J. Surg.
Pathol. 2017; 41; 482–490.
3. Bale TA, Oviedo A, Kozakewich H et al. Intracranial myxoid
mesenchymal tumors with EWSR1–CREB family gene fusions:
myxoid variant of angiomatoid ﬁbrous histiocytoma or novel
entity? Brain Pathol. 2017; https://doi.org/10.1111/bpa.12504
[Epub ahead of print].
4. Gupta K, Klimo P, Wright KD. A 2 year old girl with dysmetria
and ataxia. Brain Pathol. 2016; 26; 126–127.
Primary extra-axial, para-articular chordoma
of the knee. A case report and the review
© 2017 John Wiley & Sons Ltd
Sir: Chordoma is a rare malignant tumour demon-
strating notochordal differentiation.
It almost invari-
ably arises in the axial skeleton; however, rare
examples of primary extra-axial chordomas have been
We describe herein, for the ﬁrst time to
our knowledge, a primary conventional chordoma
arising in the synovium of the knee joint.
A 62-year-old female was admitted with swelling of
the left knee and pain. Magnetic resonance imaging
(MRI) demonstrated a large mass ﬁlling the knee
joint, invading the distal epiphysis and the diaphysis
Histopathology, 72, 878–888.