Spindle cell lipoma of the parapharyngeal space: First report of a case.

Abstract

Spindle cell lipomas are usually located in the subcutaneous tissue of the back, shoulders, and neck. To our knowledge, the presence of such a tumor in the parapharyngeal space has not yet been described. We evaluated a 45-year-old man with a tender swelling of the right parotid area that had reached the submandibular area. Clinical examination and magnetic resonance imaging revealed the presence of a tumor that coated the parotid area laterally and extended into the center of the parapharyngeal space, thus causing a dislocation of the pharyngeal muscles and mucosa. We performed a total parotidectomy and submandibulectomy on the right side and extirpated the parapharyngeal tumor. We were able to spare the facial nerve, and no facial paralysis occurred. Histologic examination revealed an atypical lipomatous tumor with a remarkably large portion of spindles.

Introduction

Spindle cell lipoma was first described by Enzinger and Harvey in 1975 as a variant of the typical benign lipoma. [1] Its histologic pattern features mature, univacuolar fat cells and fibroblast-like spindle cells in a matrix of collagen and mucoid material. The tumor is localized predominantly in the subcutaneous tissue of the back, shoulders, and neck. [2] To our knowledge, no other case of a lipomatous tumor arising in the parapharyngeal space has thus far been described.

Case report

A 45-year-old man was evaluated in May 1998 for a tender swelling in his right parotid area. He said that he had also experienced an ipsilateral hearing impairment for the previous 10 weeks. He reported no pain, difficulties in swallowing, or other complaints.

On external examination, we found a tender swelling of the right parotid and submandibular areas. Intraorally, we noted a tender protrusion on the right side of the soft palate that extended into the nasopharynx and was lightly palpable. Inspection of the nose, larynx, and hypopharynx revealed no pathologic processes, but we did observe otitis media with effusion in the right middle ear.

The patient's Weber's test was lateralized to the right, and the Rinne's test was positive on both sides. The eustachian tube function test (Valsalva's maneuver) was negative on the right and positive on the left.

B-mode ultrasonography detected an indistinctly demarcated lesion occupying the hyperechoic space and extending into the parotid and submandibular areas. Fineneedle aspiration revealed regular glandular epithelium and fat cells, but no pathologic tissue. A deep soft palate biopsy found nondiagnostic striated muscles, fat cells, and connective tissue, and no trace of any tumor.

Computed tomography detected a hypodense mass in the right parotid area that extended into the parapharyngeal space at the level of the oropharynx. Density measurements revealed predominantly negative Hounsfield units that corresponded to fat tissue. In addition, heterogeneous areas were present. No enlarged lymph nodes or other pathologic indications were found in the head or neck.

Signal characteristics on magnetic resonance imaging (MRI) confirmed that the lesion contained mostly fat tissue. MRI showed hyperintensity onTi-and T2-weighted spin-echo images (figure 1) and a partial signal loss on the fat-suppressed image (figure 2). Heterogeneous stripes passed through the lesion. In addition, rounded areas were localized centrally, demonstrating intermediate signal intensity and considerable contrast enhancement. The maximum dimensions of the entire tumor were 75 x 30 x 60mm, and the margins were well defined. The tumor had displaced but not infiltrated the adjacent muscles and mucous structures. No other sections of the head or neck were involved.

We performed a total parotidectomy and submandibulectomy and extirpated the parapharyngeal tumor on the right side. The facial nerve was retained intact.

Histologically, we found a conspicuously heterogeneous tumor that was marked by a predominance of mature, univacuolar fat cells and disseminated foci of spindle-shaped fibroblast-like cells (figure 3). A few scattered tumor cells contained bizarre-looking and partially hyperchromatic nuclei. Lipoblasts were virtually absent. A few mitoses could be detected. The tumor matrix appeared to be partly fibrous and partly mucoid. The pathologic-anatomic diagnosis was a typical lipomatous tumor with a prominent spindle cell component.

The surgical wound healed without complication, and all nerve functions remained intact. During the first few days postoperatively, there was an incomplete facial nerve palsy of the marginal ramus, but it disappeared rapidly after physiotherapy.

Discussion

Approximately 15% of all lipomatous tumors occur in the head and neck. [3] According to Fugemann, the benign lipomatous tumors of this region can be further subclassified as solitary or multiple classic lipomas; infiltrating or intramuscular lipomas; hibernomas; lipoblastomas (socalled fetal lipomas); and diffuse lipomas in children. [4] The classic encapsulated lipomas are among the most common mesenchymal tumors.

Most lipomas are localized in the subcutaneous tissue of the back, shoulders, and neck. In rare cases, they affect the oral cavity, [5] tonsillar area, [6] parotid area, [7] hypopharynx, [8] larynx, [9-11] and nasopharynx. [12] Lipomas of the parapharyngeal space are very rare; only five cases have been described. [13-17] and osteolipomas [19] of the parapharyngeal space are extremely rare.

The spindle cell lipoma is a variant of the classic lipoma, and it can easily be mistaken for a liposarcoma. Enzinger and Harvey first described this relatively unusual lipomatous tumor in 1975. [1] Only 1.5% of all lipomas are spindle cell lipomas. [20] In 75% of all cases, spindle cell lipomas are localized in the areas of the back, shoulders, and neck. [20] This tumor has a particularly high frequency in men between the ages of 40 and 70 years. Spindle cell lipomas in the mucoid tissues of the head and neck are very rare; they have been described in the oral cavity, [3,21-25] palatine tonsil, [26] and larynx. [27]

To the best of our knowledge, no case of a spindle cell lipoma of the parapharyngeal space has thus far been described. Fletcher and Martin-Bates analyzed data obtained on lipomatous tumors at St. Thomas's Hospital Medical School in London from 1961 to 1986. [20] They discovered 41 cases of spindle cell lipoma in a total of 2,478 lipomatous tumors, and none of them had been localized in the parapharyngeal space.

Histologically, lipomas consist of a lobular proliferation of mature, univacuolar fat cells in a fibrous connective tissue stroma. Terms such as fibrolipoma, hemangiolipoma, and myxolipoma are used when additional histologic components are apparent. Spindle cell lipomas and fibrolipomas are morphologically similar because both have a stroma rich in collagen fibrils. They can be distinguished from each other by the presence or absence of spindle-like fibroblasts. [22]

It is of major importance that spindle cell lipomas can be mistaken for liposarcomas both clinically and histologically. Spindle cell lipomas are characterized by bundles of relatively uniform spindle cells, broad collagen fibrils, and the absence of lipoblasts, which are a main diagnostic feature of liposarcomas. [20,22] Plexiform, [28] nodular, [28] and pseudoangiomatous [29-31] variants of spindle cell lipomas have been described.

As multiple lipomas, multiple spindle cell lipomas often occur among related individuals. Fanburg-Smith et al reported on four patients in a single family who were found to have multiple spindle cell lipomas and three additional patients with a comparable family history. [32]

The treatment of choice for spindle cell lipoma is a complete local excision. Recurrences are very rare, but the possibility cannot be dismissed. Enzinger and Harvey [1] found no recurrences in 63 operated spindle cell lipomas, and Fletcher and Martin-Bates [20] found only one recurrence in 41 tumors.

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