The Laryngoscope C 2012 The American Laryngological, V Rhinological and Otological Society, Inc. Lipomatous Lesions of the Parotid Gland: Analysis of 70 Cases Sidney J. Starkman, BS; Steven M. Olsen, MD; Jean E. Lewis, MD; Kerry D. Olsen, MD; Alain Sabri, MD Objectives/Hypothesis: To investigate presenting signs and symptoms, preoperative workup, operative therapy, and morbidity of benign and malignant lipomatous lesions of the parotid gland. Study Design: Medical literature review and retrospective chart review for all patients who underwent surgery for lipomatous lesions of the parotid gland at our institution from 1959 to 2009. Methods: Seventy patients underwent surgery for such lesions. Histologic sections were stained with hematoxylin-eosin and reviewed, and clinical information was obtained from hospital medical records for each case. Results: Forty-nine patients (70.0%) were male and 21 (30.0%) female (mean age, 49.9 years). Of the lesions, 43 (63.2%) were intraparotid, 25 (36.8%) periparotid, 69 (98.6%) unilateral, and 1 (1.4%) bilateral (average size, 3.7 cm). Fiftynine patients were treated with superficial or partial superficial parotidectomy, 10 were treated with total parotidectomy, and one was treated with parapharyngeal space dissection. Complications included six cases (8.6%) of facial paresis or paralysis and two cases of hematoma. No lesions recurred. Conclusions: We present the largest series, to our knowledge, of lipomatous lesions of the parotid gland. These masses, although rare, should be considered in the evaluation of a parotid mass. This series provides insight into the clinical presentation, diagnostic evaluation, and surgical treatment of parotid lipomatous lesions. Surgical extent depends on lesion location in the gland. Lipomatous masses can be effectively treated surgically with low morbidity and high cure rates. Key Words: Fatty tumor, lipoma, neoplasms, parotid gland, tumors.. Level of Evidence: 4 Laryngoscope, 123:651–656, 2013 INTRODUCTION Lipomatous tumors are the most common neoplasms of mesenchymal origin. Of lipomas, 13% arise in the head and neck, with the posterior neck being the most common subsite.1,2 Lipomas are composed of a benign collection of adipose tissue that may be surrounded by a fibrous capsule. Diagnosis is based on clinical and radiographic evidence and is confirmed with histopathologic analysis. Lipomas tend to exhibit slow growth, are often asymptomatic, and on examination are generally well-circumscribed soft lesions. Radiographic imaging— particularly computed tomography (CT) and magnetic resonance imaging (MRI)—can be suggestive of this diagnosis. Lipomas of the parotid gland are rare. The medical literature reports that they comprise 0.5% to 4.4% of all parotid masses. Most cases reported in the literature are single cases, with the largest series to date reporting 32 cases of lipomatous tumors in the parotid region. We report our institution’s experience with 70 lipomatous lesions of the parotid gland from 1959 until 2009. MATERIALS AND METHODS This study was approved by the institutional review board and was conducted in compliance with board guidelines. A retrospective chart review of 70 cases was performed. Inclusion criteria required that patients had undergone parotid surgery at our institution for removal of a lipomatous lesion of the parotid between 1959 and 2009. Patient data included age at diagnosis, sex, and clinical signs and symptoms, including size, laterality, facial nerve status, treatment extent, intraoperative finding, histopathologic findings, and treatment morbidity and efficacy. Follow-up was obtained either by subsequent visit at our institution or through correspondence of medical records with the patient’s home hospitals. Among 70 patients who underwent treatment of parotid lesions, 16 patients were lost to long-term follow-up. The other 54 patients had a median followup period of 68.0 months (range, 1 month–23.2 years). RESULTS From the Department of Otolaryngology–Head and Neck Surgery (S.M.O., K.D.O.), Division of Anatomic Pathology (J.E.L.), and Mayo Medical School, College of Medicine (S.J.S.), Mayo Clinic, Rochester, Minnesota; and Department of Otolaryngology–Head and Neck Surgery (A.S.), American University of Beirut, Beirut, Lebanon. Editor’s Note: This Manuscript was accepted for publication August 13, 2012. The authors have no funding, financial relationships, or conflicts of interest to disclose. Send correspondence to Alain Sabri, MD, Department of Otolaryngology–Head and Neck Surgery, American Academy of Beirut Medical Center, Cairo Street, Beirut, Lebanon. E-mail: [email protected] DOI: 10.1002/lary.23723 Laryngoscope 123: March 2013 Patient Demographic Characteristics The male to female ratio was 2.5:1. Age range at lesion diagnosis was 7.4 through 89.5 years (mean age at symptom onset, 49.9 years) (Table I). Patients included three children younger than 16 years. Across the cohort, most patients were white. No patient had a family history positive for lipomas. However, 18 patients (25.7%) had at least one medical comorbidity, and eight (11.4%) had a history of diabetes mellitus, 10 (14.3%) had hypercholesterolemia, and one (1.4%) had polycythemia vera. Eleven patients were current smokers, 26 Starkman et al.: Lipomatous Lesions of the Parotid Gland 651 TABLE I. Demographic Characteristics of 70 Patients With Lipomatous Masses. Characteristic TABLE III. Lesion Characteristics (N 5 70). Location Patients, No. (%) Ethnicity (n ¼ 68)* White 67 (98.5) Asian Age range, yr 1 (1.5) Children, 16 3 (4.3) 67 (95.7) Male 49 (70.0) Female 21 (30.0) Presentation of Neck Mass Table II summarizes the presenting symptoms of the patients. Sixty-six patients (94.3%) presented with neck mass as their chief concern. One patient had facial nerve symptoms, which included facial twitching without clinically evident facial nerve weakness. The mean duration of symptoms before presentation was 3.3 years (range, 1 month–30 years). Lesion Characteristics Among all patients, 50.0% had right parotid involvement, 48.6% had left parotid involvement, and one patient (1.4%) had bilateral involvement (Table III). Lipomatous masses involved only the superficial lobe in 92.5% of cases; the involved area was unrecorded in three cases. In 36.8% of cases, the mass was extraparotid, arising from periparotid subcutaneous fat tissue but adjacent to or involving parotid tissue. Average dimensions of the lipomas were 3.7 2.8 1.6 cm (smallest, 0.8 0.8 0.8 cm; largest, 16.5 7.5 2.5 cm) (Fig. 1). Six patients also had a lipoma at other sites (the back [n ¼ 3], the trunk [n ¼ 2], and the neck [n ¼ 1]). TABLE II. Presenting Symptoms of Patients With Lipomatous Masses (N 5 70). Patients, No. (%) 66 (94.3) 43 (61.4) Pain 3 (4.3) Facial nerve signs 1 (1.4) Laryngoscope 123: March 2013 652 25 (36.8) Superficial lobe† Deep lobe† 62 (92.5) 3 (4.5) Right parotid gland Left parotid gland 2 (3.0) 35 (50.0) 34 (48.6) 1 (1.4) *Two patients had indeterminate intra- or periparotid location (n ¼ 68). † Three patients had unrecorded superficial or deep lobe involvement (n ¼ 67). were past smokers, and 33 were never smokers. Patients with a history of smoking had an average pack-year history of 24.8 (range, 2–80 pack-years). Among the 67 patients who reported their drinking history, 20 were nondrinkers, 13 reported one drink per month, 13 reported several drinks per month, 12 reported several drinks per week, and nine reported more than several drinks per week. Neck mass Lesion size progression 43 (63.2) Periparotid* Bilateral parotid glands *Two patients had no ethnicity recorded. Presenting Symptom Intraparotid* Superficial and deep lobe† Adults, >16 Sex Patients, No. (%) Treatment Eighteen patients underwent preoperative imaging (11 had CT and seven had MRI). Among the 52 patients without preoperative imaging, only 19.2% had the appropriate preoperative diagnosis of lipoma. Among those who had CT, a statistically significant improved rate of preoperative diagnosis was achieved, with 63.6% of patients receiving an accurate diagnosis (P ¼ .003). Of patients with MRI preoperatively, an improved rate of diagnosis was seen, but results did not achieve statistical significance, with 42.9% of lipomas correctly identified (P ¼ .42). Ten patients had fine-needle aspiration (FNA) of the parotid mass; five results were indeterminate, three were suggestive of another benign mass, one was correctly suggestive of lipoma, and one was correctly suggestive of liposarcoma. The performed surgical procedures were superficial parotidectomy (n ¼ 51), total parotidectomy (n ¼ 10), partial superficial parotidectomy (n ¼ 8), and parapharyngeal space dissection (n ¼ 1). Ages at surgery ranged from 14.7 to 89.6 years (mean, 56.5 years). At the time of the surgical operations, 100% of patients had the parotid masses completely removed. Pathologic Findings Pathologic examination showed standard lipoma histologic features in 63 cases (Table IV). Variations included sialadenosis, fibrolipoma, sialolipoma, angiolipoma, and liposarcoma. Of the lipomatous lesions, 54 were without a completely enveloping capsule and 16 were fully encapsulated. Pathologic investigation showed that the locations were intraparotid in 43 cases, extraparotid in 25 cases, and indeterminate in two cases. Follow-up Short-term treatment morbidities included two cases of hematoma, four cases of transient facial paresis, and two cases of transient facial paralysis, with full recovery of facial nerve function in all cases at last follow-up (Table V). Eight of 61 patients who underwent superficial or total parotidectomy had some immediate postoperative sequelae, although none of the nine Starkman et al.: Lipomatous Lesions of the Parotid Gland Fig. 1. Intraoperative image of intraparotid lipoma. [Color figure can be viewed in the online issue, which is available at wileyonlinelibrary.com.] patients who underwent partial superficial parotidectomy or parapharyngeal space dissection had postoperative sequelae. In addition, two (10.0%) of 20 patients with a correct preoperative diagnosis had shortterm postoperative complications, and six (12.2%) of 49 patients with unspecific preoperative diagnoses had complications. Among the 54 cases with follow-up for more than one month, there were no recurrences for patients treated at our institution (median follow-up, 68.0 months; range, 1 month–23.2 years). One patient had a tumor incompletely resected at an outside institution and presented to our institution for surgical management after tumor persistence. After complete removal, the tumor did not recur. Among the three pediatric patients, there were no cases of postoperative morbidity or recurrence. DISCUSSION Lipoma is the most common soft tissue tumor in the body. It has been reported in virtually every organ,1 with 13% of cases presenting in the head and neck area2 and mainly in the posterior neck.3 Lipomas are believed to develop as a result of hypertrophy from increased uptake of acetate and increased fatty synthesis.4 Another theory on the cause of lipoma is proliferation of misplaced islands of lipoblasts or a metaplastic transformation of connective tissue into fatty tissue.5 These lesions rarely undergo lipolysis in cases of severe malnutrition or cachexia.4,6,7 Lesion Presentation Only rarely do lipomatous masses present in the parotid area. Our experience represents, to our knowledge, the largest report of parotid lipomas to date. A previous review of 14 studies reported 76 cases of lipomas identified from a total of 6,101 parotid tumors (a prevalence rate of 1.2%).8 The largest individual series focusing on lipomas from the parotid gland reported 32 cases.9 Parotid lipomas are more common in males than females. The male to female ratio in our series was 2.5:1, a lower ratio than in the previous largest series of parotid lipomas, which reported a ratio of 10:1.9. Lipomatous tumors are generally found in adults, with a small percentage occurring in the pediatric population (4.3% TABLE V. Morbidity Incidence Rates in Various Surgical Events. Transient Facial Nerve Paresis/ Paralysis, % Hematoma, % Total Morbidity Incidence, % Superficial parotidectomy (n ¼ 51) 9.8 (n ¼ 5) 3.9 (n ¼ 2) 13.7 (n ¼ 7) Total parotidectomy (n ¼ 10) 10.0 (n ¼ 1) 0 10.0 (n ¼ 1) Partial superficial parotidectomy (n ¼ 8) 0 0 0 Parapharyngeal space dissection (n ¼ 1) 0 0 0 Surgical Event TABLE IV. Lesion Variants (N 5 70). Variant Lipoma Patients, No. (%) 63 (90.0) Sialadenosis 2 (2.9) Fibrolipoma Sialolipoma 2 (2.9) 1 (1.4) Angiolipoma 1 (1.4) Liposarcoma 1 (1.4) Laryngoscope 123: March 2013 Starkman et al.: Lipomatous Lesions of the Parotid Gland 653 in our study). They occur with equal frequency on the right and left sides of the body and rarely are identified bilaterally. Our study did not find a significant correlation between the incidence of lipomatous tumor and a history of smoking or alcohol use. Likewise, this relationship has not been reported in the literature. Clinically, lipomatous masses generally manifest as relatively asymptomatic masses. In this series, the most common presenting symptom was a parotid mass, with more than half having progressed in size. Fewer than 5% of patients noticed pain or facial nerve symptoms. On examination, lipomas are soft compressible masses with normal overlying skin. They often display a positive ‘‘slippage sign’’ when the fingers are slid gently over the edge of the tumor.1 Lipomas will be felt to slip aside when under pressure, rather than a sebaceous cyst or abscess that is tethered to surrounding tissues. Neurologic findings, including hypoesthesia and paresis, are rare,10,11 with only one case of facial paresis reported.12 These tumors are rarely considered in the differential diagnosis of parotid tumors when diagnosis is based on clinical findings only. Before any imaging is performed, the most commonly reported preoperative clinical diagnoses are pleomorphic adenoma and Warthin tumor.8,9,13 location without exposing the patient to the ionizing radiation of a CT scan.19,20 MRI also can identify the tumor capsule, enabling the clinician to distinguish tumor from surrounding fatty tissue.21 Although ultrasonography was not used in this study, the literature has demonstrated the effectiveness of this modality in preoperative evaluation of lipomatous masses. A recent study determined that sensitivity for the diagnosis of lipoma increased from 54.8% after palpation to 88.1% after ultrasonography.22 An elongated echogenic mass in the subcutaneous tissues should suggest the diagnosis of lipoma. This echogenic pattern is very similar to the pattern of subcutaneous adipose tissue. Striated echoes in the tumor, which correspond to the septa, increase the possibility of lipoma. This study showed that FNA is an inaccurate means of identifying parotid lipomas. Among 10 parotid lipomatous lesions that underwent FNA, an accurate diagnosis was obtained in only 22% (2/9) of cases. Previously, FNA has been described as inaccurate for diagnosis of parotid lipomas, largely because fat cells from lipomas are histologically indistinguishable from normal subcutaneous fat, which is expected in the FNA of a parotid mass.23 In another study, only five of nine parotid lipomatous lesions yielded an accurate diagnosis on FNA.13 Preoperative Workup Preoperative imaging and FNA of parotid masses are selectively used at our institution. We generally reserve imaging for cases of suspected malignancy or cases with suspected deep lobe or parapharyngeal involvement. In addition, FNA is generally used when malignancy is suspected or when either parotid surgery is contraindicated or the patient elects for observation. Thus, the majority of patients in this series did not undergo preoperative imaging or FNA. Preoperative use of CT in the present study showed a significantly higher rate of accurate preoperative diagnosis of parotid lipoma (P ¼ .003). MRI also improved the rate of accurate preoperative diagnosis over baseline (preoperative rate vs. baseline, 42.9% vs. 19.2%), although the results did not reach statistical significance. The lack of significance is likely due to the small sample (n ¼ 7); a larger sample may yield a more significant result. CT imaging of lipomas reveals a hypodense mass (between 150 and 50 Hounsfield units), which is considered diagnostic by most investigators.3,14,15 The exception is fibrolipoma, which may show a contradictory high density on CT scan, secondary to the increased amount of fibrotic tissue in the tumor.16 Lipomas do not enhance with injection of contrast medium except in cases of angiolipomas.17 In addition to aiding in diagnosis, CT scan helps in defining the location and extent of the tumor.18 On MRI, lipomas show a high T1 and low T2 signal characteristic of fatty tissue that is comparable in signal intensity to subcutaneous fat. The fat suppression sequence of lipomatous lesions demonstrated on MRI clearly distinguishes these masses from other types of tumors. MRI provides information about tumor size and Laryngoscope 123: March 2013 654 Histologic Features Of lipomatous tumors in the parotid gland, 90% were pathologically determined to be standard lipomas; the others were classified as different variants. Histologically, parotid lipomas consist of circumscribed masses of mature adipose tissue, often with a thin fibrous capsule at the margin, differentiating them from simple aggregations of adipose tissue.8,24,25 We found that 22.9% (16/70) of lesions were well encapsulated, a finding determined histologically. Several unusual variants of lipomatous masses were found. Our series included two cases of sialadenosis—one case in an adult with diabetes mellitus and the other case in an otherwise-healthy 15-year-old child. In each case, the patient underwent complete lesion excision and had no complications or recurrence. Sialadenosis is defined by characteristic swelling of the acini, together with changes in the cytoplasm of the acinar cells. In cases of longer duration, fatty infiltration becomes predominant.26 Sialadenosis can occur secondary to a metabolic disease (e.g., diabetes, alcoholism, malnutrition, drug adverse effect)3,13 but has also been reported as a congenital condition.27 Other uncommon variants of lipomatous tumors that our series included were two cases of fibrolipoma, one case of angiolipoma, and one case of sialolipoma. Sialolipomas are rare salivary gland tumors defined histologically by mature adipocytes encasing normal salivary glandular components.28 They most commonly affect the parotid gland and present in adults as a slowgrowing, asymptomatic swelling. Angiolipomas have been reported as a congenital mass.17 Chondrolipoma and myelolipoma are lipoma variants that have not been Starkman et al.: Lipomatous Lesions of the Parotid Gland reported in the parotid gland. Multiple rare parotid lipoma variants have been described in the literature, including fibrolipoma, angiolipoma,29 spindle cell lipoma,30 pleomorphic lipoma (believed to be a variant of spindle cell lipoma),31,32 lipoblastoma (an immature fatty tumor),14,33 and osteolipoma.34 Molecular biological analysis has been useful in evaluation and diagnosis of these tumor subtypes. For example, lipoblastomas are pediatric neoplasms resulting from transformation of adipocytes, originating with PLAG1 activation (presumably resulting from transcriptional upregulation).35 One case of liposarcoma was found in the present study, occurring in an 89-year-old woman and presenting as a progressive mass over 6 months. This patient underwent complete surgical tumor excision and did not show any signs of subsequent recurrence. Liposarcomas are believed to develop de novo, rather than as malignant transformation of benign fatty tissue.5 Few cases of liposarcoma have been reported in the literature. Stewart et al.36 found three cases reported in the literature. The literature identified 12 cases of salivary gland liposarcomas. Nine of these cases were in the parotid gland and three were in the submaxillary gland.37–41 Radiologic studies may demonstrate features suggestive of a malignancy by exhibiting areas of heterogeneous density in the lipomatous mass. Histologic subtype is the most important prognostic factor for malignant lipomatous tumors. The five liposarcoma subtypes are atypical lipomatous tumor/well-differentiated, dedifferentiated, myxoid, pleomorphic, and mixed-type liposarcomas. More favorable prognoses were found with well-differentiated, dedifferentiated, and myxoid liposarcomas. Pleomorphic and mixed-type liposarcomas, which make up <10% of all liposarcomas, carried the worst prognoses, with 5year survival rates of <25%.37 A rare lipomatous disorder that we did not encounter in our study was Madelung deformity (benign symmetrical lipomatosis). This condition is characterized by large, subcutaneous, fatty masses distributed around the neck, shoulders, upper extremities, and upper dorsal regions, mainly affecting middle-aged men (male to female ratio, 15:1) with a history of alcoholism.42 It has been found to present bilaterally in the parotid regions.43 The pathogenesis of Madelung deformity is unclear. Treatment This study showed the efficacy of surgical treatment of lipomatous masses. Every lesion was treated with complete surgical excision through parotidectomy, partial superficial parotidectomy, or parapharyngeal space dissection. No cases of recurrence were found among the 70 lipomatous lesions. The sole case of liposarcoma was treated with total parotidectomy and had no recurrence. Prior cases of parotid liposarcoma have been treated with complete surgical excision successfully and without recurrence.40,44 We believe that the extent of surgery should be determined at the time of operation with dual goals of Laryngoscope 123: March 2013 complete mass resection (when possible, with a cuff of normal parotid tissue around the mass) and facial nerve preservation. The amount of parotid gland removed is dictated by lesion size and location and the prior two operative factors. We do not advocate intraparotid lumpectomy alone. Most investigators recommend superficial parotidectomy for tumors located within the superficial lobe, with dissection and preservation of the facial nerve 8,15,45 and total parotidectomy for deep lobe tumors. We and other investigators also recommend partial parotidectomy for select masses (e.g., parotid tail lesions) in the superficial lobe and the deep lobe.45 For certain tumors, the superficial lobe can also be repositioned over the nerve after resection of a deep lobe tumor, to prevent facial depression.46 Management of periparotid lesions is less debatable, with complete excision cited as an effective treatment.15 Postoperative complications in the present study were uncommon. The nine patients who had postoperative morbidity had received parotidectomy procedures for intraparotid lipomas rather than simple excision of periparotid tumors. Postoperative complications were similar to other studies of parotidectomies for benign tumors, including transient facial nerve weakness and Frey syndrome.47 Of note, the prevalence of Frey syndrome in our study was lower than would be expected. The medical literature has found the incidence of Frey syndrome after parotidectomy to be about 23.5%.48 This lower rate could be due to the referral basis of our institution with follow-up performed at other centers. Additionally, approximately half of Frey syndrome cases can be subclinical and may not have been reported. Facial nerve weakness has been shown to be more common after resection of deep lobe tumors.21 CONCLUSION We present, to our knowledge, the largest series of lipomatous lesions of the parotid gland. The most common presentations of these lesions were painless masses, with progression in size over time. FNA was noticeably inaccurate in preoperative diagnosis. However, CT and MRI can be useful for diagnosis. Preoperative imaging can be particularly useful in identifying size, location, and even the histologic characteristics of lipomatous lesions. Imaging can assist in planning the extent of the surgery, particularly in periparotid lesions that require extracapsular dissection. Treatment of benign lipomatous lesions is indicated to correct cosmetic reports due to unpleasant physical appearance or when preoperative diagnosis is inconclusive. Intraparotid lipomas require standard parotidectomy procedures. Complications are rare and recurrences even more so. BIBLIOGRAPHY 1. Adebamowo CA, Ladipo JK, Ajao OG. Parotid lipoma: a report of two cases. East Afr Med J 1994;71:210–211. 2. de Jong AL, Park A, Taylor G, Forte V. Lipomas of the head and neck in children. Int J Pediatr Otorhinolaryngol 1998;43:53–60. 3. Som PM, Scherl MP, Rao VM, Biller HF. Rare presentations of ordinary lipomas of the head and neck: a review. AJNR Am J Neuroradiol 1986; 7:657–664. Starkman et al.: Lipomatous Lesions of the Parotid Gland 655 4. Das Gupta TK. Tumors and tumor-like conditions of the adipose tissue. Curr Probl Surg 1970;7:1–60. 5. Ashley DJB. 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