Isolated hypopharynx lipoma: a case presentation and literature review

Lipomas are the most common benign mesenchymal tumors. They are defined as subcutaneous neoplasms of mature adipocyte cells that can occur wherever fatty tissue is. Lipomas are rare in the upper aerodigestive tract. Usually asymptomatic, they may be painful, uncomfortable, or even life-threatening especially if voluminous and located in the upper aerodigestive tract. A 67-year-old female patient has presented with dyspnea on mild effort and chronic orthopnea. The physical examination was normal while the fiber optic endoscopy revealed a submucosal round-shaped mass rising from the left side of the post-cricoid region. CT scan revealed a well-circumscribed fatty mass of the left piriform sinus for which the patient underwent an endoscopic transoral approach for a complete removal with good results. Pharyngeal lipomas are rare entities that might be life-threatening. Although clinical manifestations are not specific, imaging techniques, especially MRI, help set the diagnosis showing a fatty mass of the upper aerodigestive tract. However, pathology examination is crucial to rule out low-grade liposarcomas. Surgical management is not well-codified and has benefited from the development of endoscopic techniques.


Background
Lipomas are the most frequent mesenchymal benign tumors. They can develop in all fatty areas of the body, be solitary or multiple. They are primitive in the vast majority of cases and occur mainly in adults between 40 and 60 years of age [1]. Malignant transformation has never been described. Very rarely, in the head and neck region, they can be infiltrative [2,3]. They do not regress spontaneously. Their prevalence is estimated at 0.6% of neoplasms [4,5]. A scarcity is more marked in the ORL area, particularly the pharyngolaryngeal location.
We present the case of a pharyngeal lipoma involving the left piriform sinus diagnosed in a 67-year-old female patient presenting with mild exertional dyspnea and orthopnea, for which she underwent a complete endoscopic removal with a satisfactory clinical outcome.

Case presentation
A female patient in her sixties with no significant medical history was referred to the ENT outpatient clinic by her cardiologist for chronic orthopnea and dyspnea on mild physical effort associated with normal cardiac functioning. The patient reported a 05-year history of persistent pharyngeal foreign body sensation with recent snoring and sleep apnea. Otherwise, no other symptoms such as dysphagia, dysphonia, cough, or expectorations were described.
Physical examination disclosed no cervical lymphadenopathies and no goiter. Fiber optic endoscopy revealed a submucosal round-shaped mass rising from the left side of the post-cricoid region. The tumor was covered by normal mucosa and was moving up and down

Open Access
The Egyptian Journal of Otolaryngology during swallowing and respiration. The mass filled the supraglottic region during inspiration and disappeared during swallowing (Videos 1 and 2). For further characterization of the tumor, a cervical CT scan with contrast injection was ordered. It showed a low-attenuation mass that rose from the left aryepiglottic fold (Figs. 1 and 2) with very thin septa, scattered small areas of soft tissue density, and thin capsule which made it hard to distinguish from the surrounding air in the upper aerodigestive tract.
The patient underwent an endoscopic transoral approach under general anesthesia for the complete removal of the tumor and the exceeding overlying pharyngeal mucosa. The tumor has a small peduncle with a narrow base originating from the post-cricoid area (Fig. 3). No sutures were placed in the root of the peduncle. The postoperative course was uneventful. The patient received antibiotics and paracetamol for 1 week and anti-reflux medication until complete healing of the wound. A feeding tube was used for 3 days; then, oral feeding was allowed; and the patient was discharged from the hospital. However, non-spicy mixed food was recommended for 2 weeks.    Histopathology examination (Fig. 4) confirmed the diagnosis of lipoma characterized by the presence of lobulated, mature adipocytes with minimal connective tissue stroma, enclosed in a thin, fibrous capsule with no cellular atypia.
The patient's episodes of care timeline is reported in Fig. 5.

Discussion
Lipomas are the most common benign mesenchymal tumors [1]. They are usually presenting as subcutaneous neoplasms of mature adipocyte cells. However, they can occur wherever fatty tissue is found. In 80% of cases, they are typically subcutaneous lipomas with no particularities [1,2]. Head and neck lipomas count for 13% of all cases, mainly located in the nuchal area [6]; less frequently in the anterior cervical region, infratemporal fossa, oral cavity, and parotid gland; and even more rarely in the upper aerodigestive tract [5]. In our case, the lipoma originated from the anterior wall of the left pyriform sinus.
Lipomas are usually described as painless, slowgrowing soft tissue tumors of different sizes that are characterized by an insidious evolution. In fact, they usually remain silent and are often discovered fortuitously during a clinical examination or a radiology test. Nevertheless, lipomas of the upper aerodigestive tract may go unnoticed on CT scans due to the similarity of density between the air and the fatty portion especially in the pedunculated forms. They are most often sporadic in isolated cases. However, in 5-15% of patients, lipomas are multiple, thus described as lipomatosis, and approximately a third of these will be familial [7] as well as associated with other syndromes and diseases such as Gardner's syndrome, Bannayan-Zonana syndrome, Dercum syndrome, Cowden syndrome, Proteus syndrome, and Madelung's disease [8].
Clinically, lipomas may remain asymptomatic for a long period until reaching a considerate size; consequently, they are discovered at an advanced stage. On the other hand, for the symptomatic forms, and more precisely in the pharyngeal ones, clinical features depend on the location and the impact of these lipomas on the adjacent structures. The patient may describe a simple throat discomfort, a pharyngeal foreign body sensation or heaviness, dysphagia, and swallowing difficulty. Furthermore, some may experience life-threatening dyspnea, especially in the pedunculated forms, due to laryngeal obstruction, a complete externalization through the oropharynx as the case described by Gilberto et al. [9], or in the huge compressive forms. In this context, one case of death has been reported following asphyxia which was secondary to a voluminous and obstructive hypopharyngeal lipoma [10]. On the optic endoscopy, the lipoma appears as a well-limited, round-shaped, submucosal mass. It may be pedunculated or sessile.    Histologically, simple lipomas can be distinguished, based on their stroma, from the other benign variants including myolipoma, chondrolipoma, angiomyolipoma, adenolipoma, myxolipoma, and spindle cell lipoma [11] on the one hand. On the other hand, it is also important to rule out some malignant histology types such as liposarcoma in particular the well-differentiated cell form [12].
Concerning radiology features, lipoma is typically a well-circumscribed, round-shaped mass with homogeneous characteristics corresponding to a fat imaging with a thin capsule, very thin septa (< 2 mm), and some scattered small areas of soft tissue density. On ultrasounds, they are mostly isoechoic (28-60%) and hyperechoic (20-50%), yet they are hypoechoic in about 20% of the time [1] with no acoustic shadowing and no or minimal color Doppler flow [13]. If encapsulated, the capsule may be difficult to identify sometimes and to be distinguished from the air around in the pharyngolaryngeal area [7]. Calcification may also be present in up to 11% of cases, although more commonly associated with well-differentiated liposarcoma [7]. Moreover, avidly enhancing, thick/ nodular septa or evidence of local invasion in addition to heterogeneous echotexture, more than minimal color Doppler flow, suggests malignancy.
The diagnosis is usually indicated by clinical features and ultrasound results. However, in the upper aerodigestive tract, CT scan and MRI imaging may be helpful for a better evaluation of the mass and the surrounding structures. On CT scan, lipomas presented as fatty, homogeneous, low-attenuation masses with minimal internal soft tissue component occasionally. It may also show some areas of fat necrosis, blood vessels, and muscle fibers whereas a liposarcoma is eliminated firstly [7]. MRI can also be used as a diagnosis tool and show a high-signal mass on both T1 and T2 with saturation on fat-saturated sequences. In fact, MRI represents the main imaging tool for lipoma diagnosis with or without atypical features. As a matter of fact, when no suspicious features are present, MRI is 100% specific regarding the diagnosis of lipoma [14]. In the opposite case, if suspicious features of malignancy are present, the specificity of MRI is lower since some masses with atypical features will nonetheless be simple lipomas, while the sensitivity is still 100% [14].
Well-differentiated liposarcomas, which represent the main and most dangerous differential diagnosis of lipomas, have high chances of local recurrence and a possibility of delayed dedifferentiation after the initial treatment [15]. Because of the differences not only in the treatment's modalities, but also concerning the prognosis and the follow-up protocols, it is very important to distinguish simple lipomas from well-differentiated liposarcomas. In fact, immunohistochemistry describes the liposarcoma subtypes disclosing different morphologies, genetics, clinical behavior, pattern of disease progression, response to treatment, and 5-year survival rate [15,16].
In the upper aerodigestive tract, surgical management presents a challenge regarding the security of the upper airways, the possibility of intubation, the possibility of jet ventilation use, and endoscopic surgery sittings. Since this is a rare entity, each case should be considered unique and have to be managed individually. Nonetheless, it seems that hypopharyngeal lipomas tend to rise from the post-cricoid region [15,16]. Therefore, securing the upper airways might be challenging if the tumor is large and has no peduncle which implies a transitory tracheostomy. Also, the lent of the peduncle base might condition the necessity or not to put mucosal sutures or surgical glue in order to prevent salivary fistula. Surgical excision might be performed using endoscopic cold instruments (micro scissors, sickle). However, CO 2 laser offers better ergonomics especially regarding bleeding control. Table 1 summarizes all hypopharyngeal lipomas reported in the literature to date.

Conclusion
Pharyngeal lipomas are rare entities that might be lifethreatening. Although clinical manifestations are not specific, imaging techniques, especially MRI, help set the diagnosis showing a fatty mass of the upper aerodigestive tract. However, pathology examination is crucial to rule out low-grade liposarcomas. Surgical management is not well-codified and has benefitted from the development of endoscopic techniques.

Patient's perspective
I recently had breathing difficulty so I went seeing my cardiologist. After routine work up, he advised me to see an otolaryngologist as my results were normal. In the ORL outpatient clinic, doctor performed a fibroendoscopy and discovered a tumor. I was scared of being diagnosed with cancer. I must say that I had swallowing difficulties that I didn't took seriously. I had a CT scan and the ORL told me I had a fatty mass that he can remove pretty easily. I got the surgery. Post operatively, I had mild pain but my swallowing and breathing difficulties were resolved. I was discharged from the hospital within 3 days. I went back to see my doctor within 10 days for pathology results. He appeased my worries as the tumor was benign. Since surgery my breathing and swallowing symptoms were completely resolved.