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\begin{document}

\title{Solitary Fibrous Tumor of Parapharyngeal Space: A Rare Case Report}



\author[1]{Gunjan  Dwivedi}%
\author[1]{Arnab  Bandopadhyay}%
\author[1]{Tanushri Mukherjee}%
\affil[1]{Command Hospital Kolkata}%


\vspace{-1em}



  
  \date{May 26, 2024}


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\selectlanguage{english}
\begin{abstract}
Solitary fibrous tumors are rare vascular tumours.Their occurrence in
parapharyngeal space is very rare.Hence, they should also be considered
in the differential diagnosis of parapharyngeal soft tissue tumours.%
\end{abstract}%



\sloppy


\textbf{Title}Solitary Fibrous Tumor of Parapharyngeal Space: A Rare
Case Report

\textbf{Abstract}

Solitary fibrous tumors are rare vascular tumours, earlier referred to
as hemangiopericytoma. Their occurrence in parapharyngeal space is very
rare. Hence, they should also be considered in the differential
diagnosis of parapharyngeal soft tissue tumours. This case is being
reported to bring out an extremely rare vascular tumour at rare site and
represents a surgical challenge because of difficult access in
parapharyngeal space with difficult planes between tumour and rest of
parapharyngeal space, approach to it is also difficult

\textbf{Key words}

Solitary fibrous tumor, Parapharyngeal space, Vascular tumor, Spindle
cell tumor, Embolisation

\textbf{Introduction}

Solitary fibrous tumors (SFT) are rare spindle cell neoplasms {[}1{]}.
SFTs are generally associated with serosal surfaces, but in recent years
it has been reported in extra pleural sites such as the liver, adrenal
gland. SFT has an incidence of 2.8/100000 population, with similar rates
between men and women, and it is more frequent during the 5--6th decade.
Head and neck SFTs accounts for 6\% of all SFT in human body {[}2{]}. It
is often misdiagnosed due to its microscopic resemblance to several
other spindle cell tumors. Their occurrence in parapharyngeal space is
extremely rare, difficult site to reach when tumour is reaching up to
skull base and far medially. Herein, we present a rare case of SFT
located in the left parapharyngeal space that was successfully excised
by combined approach. This case proposes that, although rare, SFT should
be considered in the differential diagnosis of soft-tissue tumours in
the parapharyngeal space.

\textbf{Case report}

25 years old male, presented with progressively increasing painless
swelling in left parotid region of three years duration. On examination,
a 9x9cm swelling was seen in left parotid region which was non-tender,
smooth surface, soft in consistency, not adherent to overlying skin.
Oropharyngeal examination revealed a smooth bulge on left side of soft
palate. (Fig 1) Rest of ENT sites were normal and no constitutional
symptoms. Neck examination did not reveal any palpable nodes.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image1/image1}

\end{center}
\end{figure}

\textbf{Fig 1.} (a) Swelling of size 9x9cm in left parotid region which
was non-tender, soft in consistency, smooth surface, (b) Smooth bulge
seen over soft palate left side

Patient had reported with CECT scan of neck which showed heterogeneously
enhancing lesion 35x44x47mm in size epicentered in left parapharyngeal
space, pushing the parotid laterally with large number of arteries/
veins seen in and around the lesion. Lesion was in contact with left
styloid and carotid space, superiorly abutting base of skull and
medially pterygoid plates and sphenoid.

MRI neck showed hyperintense lesion in T1 and T2 of size 48x68x45mm with
heterogenous post contrast enhancement. It was anteriorly closely
abutting masseter with loss of fat planes, anteromedially involving
prestyloid parapharyngeal space and masticator space displacing
temporalis, medially eroding pterygoid plates displacing lateral and
medial pterygoid muscle and narrowing oropharyngeal airway. It was
closely abutting carotid vessels which were narrowed. Superiorly it was
reaching base of skull without intracranial extension. Mandibular ramus
was thinned out. (Fig 2a, 2b)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image2/image2}

\end{center}
\end{figure}

\textbf{Fig 2.} MRI Base of skull to root of neck (a)T2 WI showing a
lobulated heterogeneously hyperintense lesion in left parotid gland with
internal flow voids suggestive of internal vessels, (b)T1WI post
contrast, showing significant post contrast enhancement

CT angiography of neck revealed possibilities of a neoplasm with high
vascularity- high flow vascular malformation. It was diagnosed as a case
of left parapharyngeal arterio- venous malformation, a plan of excision
of tumor with prior embolization was made. Digital subtraction
angiography (DSA) showed hyper vascular tumor pattern in left parotid
region with predominant supply from hypertrophied right ECA branch
(posterior auricular artery) with minor supply from few twigs of facial
artery and no supply from right vertebral artery noted.

Patient underwent pre surgical embolization by contralateral
approach-right femoral artery. Particle embolization done with 300- 500
micro and 500-700 micro PVA particles and posterior auricular artery was
blocked. Check angiography revealed \textgreater{}90\% reduction in
tumor blush. (Fig 3a, 3b)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image3/image3}

\end{center}
\end{figure}

\textbf{Fig 3.} \textbf{Digital Subtraction Angiography:} (a)\textbf{Pre
embolization:} Coronal- showing feeding vessels in the tumour mass
originating from the ECA with a significant tumour blush,
(b)\textbf{Post embolization:} post coil embolization showing
significant reduction in the feeding vessels and the tumour blush

The tumor excision required combined approach (Transparotid,
Transcervical and Mandibular swing approach) (Fig 4a, 4b, 4c) with intra
op findings of large vascular tumor of size 8.0x7.5cm (Fig 5a, 5b) in
left parapharyngeal space infiltrating into deep lobe of parotid
laterally, reaching pterygoid plate medially extending up to skull base
superiorly and up to angle of mandible inferiorly. Facial nerve was
identified and through transparotid approach tumor was reached
preserving all the branches of facial nerve. Transcervical and mandible
swing were also required for adequate access and excision of the tumor
as it was adherent with lot of vascularity. Paramedian mandibulotomy was
employed for mandible swing. Brisk bleeding encountered during surgery
from dilated tumor vessels.\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image4/image4}

\end{center}
\end{figure}

\textbf{Fig 4.} Excision of tumor via combined (a)Transcervical, (b)
Trans parotid and (c) Mandibular swing approach\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image5/image5}

\end{center}
\end{figure}

\textbf{Fig 5a,b .} Large vascular tumor of size 8.0x6.5cm in left
parapharyngeal space infiltrating into deep lobe of parotid laterally,
reaching pterygoid plate medially extending up to skull base superiorly
and up to angle of mandible inferiorly

Histopathology of excised specimen revealed a well circumscribed tumor
composed of haphazardly arranged spindle shaped cells with attenuated
nuclei in a collagenized background with hyper and hypo cellular areas
were seen. The stroma showed presence of hemangiopericytomatous pattern
of blood vessels. Mitosis was \textless{}3/hpf. On IHC, the cells were
positive for CD34, negative for SMA, Chromogranin, synaptophysin, CD31,
Vimentin and Ki index-2\%. Therefore, it was diagnosed as Solitary
fibrous tumor. (Fig 6a, 6b)\selectlanguage{english}
\begin{figure}[H]
\begin{center}
\includegraphics[width=0.70\columnwidth]{figures/image6/image6}

\end{center}
\end{figure}

\textbf{Fig 6.} (a)(100X) IHC for CD34- Tumor cells showing membranous
immunopositivity, (b)(40X) Photomicrograph showing a spindle cell tumor
in a \textbf{hemangiopericytomatous} pattern. Blood vessels are dilated
and thin walled

Discussion

Solitary fibrous tumors (SFT) were first described in pleura by Lietaud
in 1767, followed by Wagner in 1870.{[}3{]} Klemperer and Rabin, in
1931, classified pleural tumors into two types: diffuse mesotheliomas
and localized mesotheliomas or solitary fibrous tumor {[}SFT{]}. {[}4{]}
In 1991, Witkin and Rosai were the first to report a case in the head
and neck region.

SFTs were classified as benign and malignant based on histopathological
features. Also been referred to by numerous other names, most of which
are now outdated{[}5{]}. Subsequent immunohistochemical and
ultrastructural studies have suggested that SFTs are most likely derived
from adult mesenchymal stem cells rather than mesothelium, `Solitary
fibrous tumor' is the currently preferred term.

Pleural SFTs account for about 30\% of all cases followed by meninges of
about 27\%. The most common extra-pleural and extra meningeal locations
include abdominal cavity in 20 \%, trunks in 10 \%, extremities in 8\%,
and neck in 5 \%. In the head and neck, the most common site affected is
the oral cavity {[}6{]}. SFT in pleura have a unique gross and
microscopic appearance, wherein situation is different when it affects
extra pleural sites.

Clinically extra pleural SFT may present with symptoms related to the
site of origin of tumor or with systemic symptoms such as hypoglycaemia,
arthralgia, osteoarthropathy and clubbing of fingers due to the
production of an insulin like growth factor. The systemic symptoms
usually resolve on removal of tumors. These tumors usually present as a
well-defined, palpable, painless, and slowly growing mass. Extension to
the parapharyngeal space to be suspected, if the patient develops
compression symptoms. Sleep apnoea is reported, as a result of
parapharyngeal extension of the parotid tumour {[}7{]}. Radiographic
findings are non-specific. Hence, a diagnosis of SFT is based on
histological and immunohistochemical findings. On IHC, SFTs are reactive
to CD34, Bcl2, vimentin, CD99.

England et al. {[}8{]} defined the histological criteria, still valid
today, that characterize malignant SFTs (Table 01)

To determine the risk of malignancy of each tumor, Demico in
2017{[}09{]} classified SFT into three groups according to the risks of
metastasis, which is depending on the malignant potential determined for
each tumor. (Table 02)

Follow-up is based on guidelines for soft tissue sarcomas of the
National Comprehensive Cancer Network: Low-risk tumours, an imaging test
every 6 months for 3 years, and then annually until 5 years, Medium or
high-risk tests, every 3--4 months during the first 2 years and then
every 6 months until the fifth year.

Surgery in these tumors should be planned with the aim of achieving
complete surgical resection with optimal margins as SFT can have a
potential malignant behaviour, and to avoid local recurrence.

Parapharyngeal space SFTs are very rare. Hence, they should also be
considered in the differential diagnosis of parapharyngeal soft tissue
tumors. This case is being reported to bring out an extremely rare
vascular tumor at rare site and also represents a surgical challenge
because of difficult access in parapharyngeal space with difficult
planes between tumor and rest of PPS, approach to PPS is also difficult

\textbf{Conclusion}

Solitary fibrous tumors are rare vascular tumours, earlier referred to
as hemangiopericytoma. Surgical removal is the treatment of choice to
address cosmesis and functional issues. They need to be removed as they
have malignant potential too. Prior embolization may be considered in
large and hyper vascular tumours. {[}10{]}

\textbf{Compliance with Ethical standards}

\textbf{Conflict of interest:} The authors declare that they have no
conflict of interest\textbf{.}

\textbf{Ethical Approval:} Not applicable as it involves one case report

\textbf{Informed Consent:} Informed consent was obtained from the
individual participating in the study

\textbf{Hosted file}

\verb`Figure legends.docx`  available at \url{https://authorea.com/users/564523/articles/611313-solitary-fibrous-tumor-of-parapharyngeal-space-a-rare-case-report}

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