Lipomatous Lesions of the Head and Neck

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Lipomatous Lesions of the Head and Neck
August 17, 1991
Michael G. Stewart, M.D.

Benign lipomas are by far the most common soft tissue tumor. They are common after age 40, although they may occur at any age. They are found equally in men and women. They are usually in a subcutaneous location. Recurrence is uncommon, on the order of 5%. Benign lipomas may occur anywhere in the head and neck, including the palate, the tongue, the tonsil, the larynx, and the parotid.

There are a few reports of histologically-benign lipomas which infiltrate into skeletal muscle, and which tend to recur. These are named "benign infiltrating or intramuscular lipomas." The largest series in the literature reports a recurrence rate of 62%.

There are several other reported subclassifications of benign lipomas, including angiolipoma, fibrolipoma, diffuse lipomatosis, symmetrical lipomatosis, and hibernoma. "Pleomorphic lipoma" and "spindle cell lipoma" are distinguished as benign lesions which simulate liposarcoma histologically. They occur almost exclusively in the posterior neck, shoulder, and back. They almost never recur.

There are approximately 5000 new malignant soft-tissue neoplasms each year in the United States. Liposarcomas make up 5 to 6% of these tumors. The ratio of incidence of benign lipoma to liposarcoma is 120:1. There is a slight male predominance in liposarcoma of approximately 60-40, and the mean age is in the 50s. Although the most common lipoblastic tumor in children is benign lipoblastoma, liposarcomas have been reported in children. The vast majority of liposarcomas are found in the extremities and retroperitoneum. The in cidence of head and neck liposarcoma is low: only 5.6% of over 1000 cases from the Armed Forces Institute of Pathology.

Liposarcomas take their origin from primitive mesenchymal cells and not mature fat. They are not believed to develop by malignant transformation of lipomas.

The current classification system accepted by the World Health Organization for liposarcomas consists of four subtypes: the well-differentiated and myxoid types are the low-grade liposarcomas. The round-cell and pleomorphic types are the poorly-differentiated, or high-grade liposarcomas.

Survival appears to be related to the degree of differentiation: the five-year survival for low-grade liposarcomas is about 80%, and for high-grade tumors is 0 to 20%. The local recurrence rate for low-grade tumors is approximately 50%, and these recurrences may be delayed for five or even ten years. The round cell and pleomorphic types have slightly higher recurrence rates in most series, although some authors feel that tumor location has a higher influence on recurrence rate than tumor histologic type.

Metastasis is clearly related to histologic type. The high-grade tumors do metastasize, and well-differentiated tumors apparently do not. It is important to distinguish between multicentricity and metastasis. The most common site of metastasis is to the lung. Liposarcoma almost never metastasizes to regional lymph nodes.

In 1979, in a landmark article, Evans, et al, re-classified the well-differentiated liposarcomas based on the clinical course of 30 cases from the Mayo Clinic. Well-differentiated tumors which were superficial did not metastasize or cause the death of the patient, although there were several local recurrences. These were re-named "atypical lipoma." The well-differentiated tumors located in the retroperitoneum had a high incidence of unresectable local recurrence and several deaths from tumor. They were classified "well-differentiated liposarcoma." All of these lesions were originally classified well-differentiated liposarcoma. Although widely used, Evans' classification system is not universally accepted, however.

It is important to realize that this classification scheme is both clinical and histologic. Atypical lipoma and well-differentiated liposarcoma are histologically similar; however, the clinical behavior of the tumors and the ultimate outcome of the patients appears to be different depending on the lesion's location.

There are currently only 84 total cases of head and neck liposarcoma in the literature, many of which are single case reports. There were 20 reports of laryngeal involvement; 19 of 20 cases were males, 18 of 20 were over 40 years old, and 16 arose from the supraglottic larynx. The hypopharynx or pharynx was involved in five cases. There are 21 reported cases of oral cavity involvement, 11 of which involved the cheek. The soft tissues of the neck were involved in 18 cases, and the soft tissues of the face and skull (excluding cheek) in 18.

It is very difficult to assess the overall outcome of patients with head and neck lesions because of different nomenclature, treatment and follow-up used. It is clear, however, that histologic type is very important in prognosis of head and neck liposarcoma: the only deaths and metastases were in patients with round cell or pleomorphic tumors. Patients with well-differentiated liposarcoma tended to do well, with reports of local recurrence only, although rarely these recurrences are unresectable.

There are several reports detailing the radiologic findings in lipomatous tumors, and MRI is the preferred study in recent reports. The characteristic MRI finding is a soft tissue mass with at least a portion which is isointense with normal subcutaneous fat, which means a high signal on T1-weighting. The ratio of high to low signal areas is dependent on the differentiation of the liposarcoma.

The recommended treatment for all lipomatous lesions of the head and neck is as wide an excision of the tumor as possible, trying to avoid shelling out the tumor. If the lesion is a benign lipoma, excision alone is adequate. If the final pathology is atypical lipoma, surgical excision alone is probably adequate, although atypical lipomas recur approximately 30% of the time, so the follow-up should be long-term.

If the final pathology is liposarcoma, post-operative radiation therapy should be considered in selected cases. Some reports suggest that the low-grade types are more sensitive to radiation than the high-grade types, although all types of liposarcoma are somewhat radiosensitive. Saunders, et al, have reported that palliative radiation therapy may prolong survival in unresectable tumors. Most studies do not recommend routine regional lymph node dissection. No study has ever demonstrated conclusive evidence supporting chemotherapy in the treatment of liposarcoma.

A 72-year-old white male presented with a three month history of a slowly enlarging right parotid mass. He denied pain or facial weakness. He has no history of skin cancer. Physical exam revealed a mobile 2.5 x 2.5 cm mass in the buccal portion of the parotid gland. There was no cervical adenopathy and the remainder of the head and neck exam was unremarkable.

Fine-needle aspiration of the parotid mass revealed cells suspicious for malignancy. The patient underwent superficial parotidectomy with facial nerve preservation, and the final pathology was interpreted as atypical lipoma. His post-operative course was complicated by a buccal-area sialocele, which has resolved after aspiration.

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©2001-2006 Baylor College of Medicine
Bobby R. Alford Department of Otolaryngology-Head and Neck Surgery
Mail: One Baylor Plaza, NA102, Houston, TX 77030
Phone: 713-798-5906
E-mail: oto@bcm.edu

Last modified: Feb. 14, 2006