Lupine Publishers | Journal of Otolaryngology
Lipoma of the parotid gland is extremely rare, accounting for
only 0,6% - 4,4% of all parotid tumors. We present a rare case of
lipoma of the superficial parotid lobe. A 68 - year-old man, presented
in our department with a mass of the left parotid region. Clinical
examination revealed a mobile, soft, non-tender mass in the area of the
left parotid gland. MRI concluded to a lipoma of the superficial lobe of
parotid gland. Parotidectomy preserving the facial nerve was performed.
No complication nor recurrence were noted after a follow-up of 12
months. Lipoma arising in the parotid gland is extremely rare. Resection
of this tumor requires full exposure of the facial nerve and its
branches.
Keywords: Lipoma; Parotid gland; Superficial lobe; Parotidectomy
Introduction
Lipoma is a common mesenchymal soft tissue tumor that can be
found in any part of the body. It can develop in the head and neck
region in 15–20% of cases. Rarely it can arise in the Parotid gland with
a ranging incidence from 0,6 to 4,4 % [1]. Clinical diagnosis may be
difficult. MRI is necessary, in diagnosis [2]. Surgical management of
these tumors is challenging and need meticulous dissection of the facial
nerve. We report a case of lipoma arising of the parotid gland and we
discuss through literature its clinical and therapeutic features.
Case Report
A 68 - year-old man presented with mass of the left parotid
region, which was painless slow-growing for 5 years. Clinical
examination revealed a mobile, soft, non-tender mass that measured about
6cm in diameter in the area of the left parotid gland, extending from
the ear lobule to the left mandibular angle. There was no facial
paralysis nor evidence of cervical lymphadenopathy. Magnetic resonance
imaging (MRI) showed a well-defined homogeneous lesion of the
superficial lobe of the left parotid gland with an enhanced signal on
T1- and T2-weighted sequences and weak signal on fat suppressed
sequences (Figure 1). The diagnosis of intra parotid lipoma was evoked. A
left superficial parotidectomy preserving the facial nerve was
performed. The specimen was soft, yellowish, well- circumscribed
measuring 80*34mm. Histological examination revealed a
well-circumscribed aggregate of mature adipocytes surrounded by a thin
fibrous capsule confirming the diagnosis of intraparotid lipoma. No
recurrence or complication were observed after a follow-up of 12 months.
Discussion
Lipoma is one of the most frequently encountered benign
mesenchymal tumors that may originate from adipose tissue in any part of
the body [3,4]. Rarely, it can develop in the parotid gland with
reported incidence ranging from 0,6% to 4,4% among parotid tumors [3,5].
Lipoma may occur at any age, but most frequently between 40 and 60
years with a male predominance [5,6]. Its aetiology is unknown. It can
be caused by heredity, obesity, diabetes, radiation, endocrine
disorders, insulin injection, corticosteroid therapy and trauma [7]. In
our case, we did not find any aetiological factors. Most of the reported
cases were located at the superficial parotid lobe [7]. Lipomas
involving the deep parotid lobe are extremely rare [5-8]. Clinical
diagnosis may be difficult [9], especially for tumors located at the
deep parotid lobe because it is difficult to evaluate the relationship
between these masses and the surrounding tissues. Those situated at
superficial parotid lobe usually appear as a slow growing, non-tender,
movable and well-differentiated soft mass in parotid region [3-10].
Facial paralysis and pain are uncommon signs and rarely have been
described [5-11]. This benign clinical presentation is most often
mistaken for Warthin tumor or pleomorphic adenoma [3-12]. Fine needle
aspiration cytology (FNAC) has great value in the diagnosis of parotid
tumors and requires an experienced cytologist. Its accuracy drops to
less than 50% in the cases of parotid lipomas [5-13]. On imaging, CT
scan shows hypodense, homogeneous and well delineated mass with few
septations and negative attenuation, without contrast enhancement
[3-13]. However, CT scan cannot distinguish lipoma from surrounding
adipose tissue. MRI remains the best diagnostic tool that can accurately
diagnose lipomas [5-1]. Lipomas produce strong signals on T1- and T2
weighted sequences and weak signals on fat-suppressed sequences. After
Gadolinium injection, the mass still hypointense to parotid, homogeneous
in signal and uniformly non-enhancing [3]. MRI can also clearly define
the limits of lipoma from normal adipose tissue and may be useful in
determining the appropriate surgical approach.
Figure 1: MRI of the parotid gland showing
homogeneous mass on the superficial lobe of the left parotid gland on
hyper signal
T1 and T2 and a weak signal on fat suppressed sequences. The
lesion is hypointense to parotid and uniformly non-enhancing.
Figure 2: Macroscopic findings of the resected tumor.
Histopathologic investigation reveals mature adipose tissue
separated from parotid gland parenchyma with a fibrous capsule.
Identification of a capsule may aid in distinguishing such a neoplasm
from pseudolipoma, lobular lipomatous atrophy, or lipomatosis, all of
which are unencapsulated [3]. Surgery is the treatment of choice of
parotid gland lipoma, but its modalities remain controversial [8-12]. It
should be performed by experienced surgeons because of the need for
meticulous dissection of the facial nerve branches. The postoperative
esthetic and functional results should be the major concerns [1]. Some
surgeons recommend simple enucleation of a superficial lobe parotid
lipoma with a small border of healthy parotid gland parenchyma, as this
is easy to perform because of the well-defined capsule. Other surgeons
suggest that the surgical management of parotid lipoma should be the
same as that for other parotid tumors [5]. However, it is well known
that transient facial nerve dysfunction and Frey’s syndrome may occur as
complications following surgical intervention for parotid tumors and
should be explained to the patient before operation [5]. Facial nerve
dysfunction ranged between 8.2 and 65% after parotid gland surgery for
benign tumors [10]. Therefore, it requires efforts such as facial nerve
monitoring to identify the facial nerve. Recurrence rate of parotid
lipoma after adequate resection is very low. It has been reported in 5%
in all cases when it is well-encapsulated [5-9]. Malignant
transformation into liposarcomas has been reported in few cases in the
literature [9]. Therefore, careful follow-up is recommended.
Conclusion
Lipoma of the parotid gland is a rare benign tumor, which
should be considered in the differential diagnosis of parotid gland’s
mass lesions. MRI is essential to locate the tumor, and to precise its
relationship with the facial nerve. Their management is challenging.
Definitive diagnosis can only be accomplished with histopathologic
review.
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