Cancer Genetics and Epigenetics 2017, Vol.5, No.6, 28-32
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SS appears to be frequently derived from the lower extremities, predominately the knee, usually with close
relation to tendon or tendon sheath and cystic structures, but rarely in joint cavity. Besides the common extremity
site, the head and neck region is the next frequent site. Sarcomas of the head and neck represent approximately 1%
of all head and neck malignancies. SS accounts for less than 10% of cases. Paravertebral site is the most common
region for SS in the head and neck, with the presentaion from skull base to the hypopharynx (including
pharyngeal, parapharyngeal, and the prevertebral planes; skull base and temporomandibular joint fossa)
(Tilakaratneet al., 2006; Horbinsk et al., 2008; Al-Daraji et al., 2009; Scheithaueret al., 2011; Keith et al., 2013;
Lin et al., 2013; Xiao et al., 2014). Occurences besides extremities or head and neck have also been documented,
such as thorax (including heart and lungs), even rarely within abdomen and pelvis (Witkin et al., 1989; Gaertner et
al., 1996; Nicholson et al., 1997; Nicholson et al., 1998; Fisher et al., 2004; Suster et al., 2005; Sakellaridis et al.,
2006; Company et al., 2007; Schreiberet al., 2007; Makhlouf et al., 2008; Katakura et al., 2009;Cummings et al.,
2010; Alsharief et al., 2012; Dhawan et al., 2012 Nomura et al., 2014; Crowson et al., 2015; Eravci et al., 2016).
The diagnosis of SS is generally made by its relatively distinctive, yet markedly variable histopathologic
appearance, in conjunction with the histochemical, immunohistochemistry, electron microscopy, and cytogenetic
analysis findings. Histologically, SS was originally considered a malignant tumor arising from synovial
membrane. Studies have, however, shown that it may originate from pluripotent mesenchymal cells with no
definitive association to articular surfaces or membranes. Therefore, it is notable that SS could occur in every
anatomic site.
According to some investigators, SS apparently shows epithelial differentiation, but synovial membrane does not
actually harbor epithelial cells. Thus, SS is named for its appearance, rather than the origin. Different from other
sarcomas, SS is composed of carcinoma-like epithelial cells and fibrous sarcoma-like spindle cells. Although the 2
characteristic cell types of SS are morphologically distinct, they are histogenetically similar. Basically, SS
comprises 2 major subtypes and rarer subtypes. The former include monophasic and biphasic spindle cell types;
and the latter includes monophasic epithelial, poorly differentiated, calcifying/ossifying, and myxoid types,
depending on their varying composition and degree of differentiation. The monophasic spindle cell type
composed of plenty spindle cells is the commonest subtype of SS, and has a tendency towards indistinguishable
from other tumors common to the region, such as adenocarcinoma.
Immunohistochemically, SS presents positive to cytokeratin (CK), epithelial membrane antigen (EMA), S-100,
bcl-2, CD99 and calponin. Varying from other spindle cell tumors, SS is negative to CD34.
In terms of radiological findings, the imaging features of intraventricular SS remain needed to be accumulated.
Generally, SS tends to occur in extremities, often as expansive lobulated masses, with well-defined margin, and
most frequently close to joints. Although there is no consensus on imaging, calcification has been reported
common and more easily discerned radiologically. On CT, approximately 30% of cases appear detectable
calcification, which may be focal or dispersed throughout the tumor, often with a fine, stippled, or opaque
appearance.
Magnetic resonance imaging is thought to be the imaging modality of choice for showing the internal features of
the lesion and superior soft tissue contrast. In addition, MR has a priority in the assessment for invasive
characteristics such as infiltration into the surrounding soft tissues (including muscle, adjacent bone) and adherent
to tendon or neurovascular structures. Typically, SS range from 3 to 10 cm in diameter. The lesions tend to be
small when they occur in hands or head and neck. The survival rate is regarded to be low when the lesion is more
than 4 cm. Lesions less than 1 cm in diameter which are named as “Minute” SSs are clinically considered benign
processes, such as ganglion cysts or glomus tumors. Occasionally, there is cyst formation, with smooth walled
cysts, often multiple, containing mucoid fluid or blood. Hemorrhage and necrosis can be prominent in poorly
differentiated SS, although are less prominent than in high-grade pleomorphic sarcomas.
SS is a rare cancer type, which is primarily derived from the soft tissues of the lower extremities. Ventricle is an
extremely rare localization. Cases with the presentation affecting dura and cerebellum have been characterized. To
