Anterior neck lipoma mimicking a goiter

A 57-year-old black woman was referred for evaluation of goiter with a history of an anterior neck swelling for two years associated with neck discomfort, a bad taste in the mouth and frequent belching. She denied dysphagia, odynophagia, hoarseness, shortness of breath, symptoms of hyperthyroidism or hypothyroidism, or a history of thyroid disease or neck radiation.

Stephanie L. Lee

Daniel J. Rubin

Trial of a proton-pump inhibitor by her primary care doctor failed to relieve her symptoms. Physical exam revealed a 6 x 6 cm soft, fleshy, mobile anterior neck mass extending symmetrically over the lower neck beneath the sternocleidomastoid muscles. Her neck profile resembled that seen with a goiter (see Figure 1). There were no carotid bruits and the thyroid gland was not palpable. No cervical lymphadenopathy was appreciated. Serum TSH, total T₃ and total T₄ were normal. Anti-thyroid peroxidase antibodies were not detected.

A CT scan performed two years prior to evaluation showed a 3 x 6.7 x 7.7 cm midline fat mass in the anterior neck between the strap muscles and the trachea (see Figure 2). There was no local inflammation, lymphadenopathy, or compression of adjacent structures. A 1.6 x 1 cm heterogeneous nodule was noted in the left lobe of the thyroid.

Neck ultrasound confirmed the presence of a large hypoechoic anterior neck fat mass (see Figure 3) positioned anterior to a multinodular goiter with a dominant 1.6 x 1.3 x 1.4 cm nodule in the left thyroid lobe. The nodule was inaccessible for fine-needle aspiration biopsy due to the thickness of the overlying fat mass.

Figure 1. Profile image of the neck appeared to show a lower anterior neck enlargement typically seen with a large goiter. Stephanie L. Lee

Figure 2. CT scan of neck with contrast. Axial images showed a large mass with a homogeneous, low attenuation density similar to fat. The mass measured 3.0 x 6.7 x 7.7 cm and was located within the anterior neck, between the strap muscles and larynx/trachea from the level of the clavicular heads to the hyoid. The mass did not enhance with contrast. T = trachea, JV = jugular vein, c = carotid artery, THY = thyroid gland, MASS = fat-density anterior neck mass. Stephanie L. Lee

The patient initially declined neck surgery to remove the presumed lipoma. Repeat ultrasound seven months later and CT scan 10 months later showed no change in either the fat mass or the dominant thyroid nodule.

Due to her persistent symptoms and aesthetic concern, the patient eventually underwent simultaneous surgical excision of the fat mass and left hemithyroidectomy. The excised fat mass was 10.5 x 9 x 2 cm and weighed 118 g (see Figure 4).

Histological examination confirmed mature adipose tissue consistent with lipoma. Examination of the left thyroid lobe confirmed benign multinodular goiter. One month following surgery, that patient’s symptoms were much improved.

Association made

Lipomas are slow-growing, benign tumors usually found in the subcutaneous tissue. Histologically they are composed of mature white adipose tissue arranged in lobules surrounded by a thin fibrous capsule. Given the fat composition of lipomas, it is not surprising that they may appear or grow during periods of weight gain.

Most lipomas occur sporadically, but rarely they are associated with a number of inherited conditions such as Gardner’s syndrome and hereditary multiple lipomatosis. Lipomas are the most common soft-tissue neoplasm with a prevalence of two per 100 people, accounting for about 50% of all soft-tissue tumors.

In general, there is no clear gender predilection of solitary lipomas. However, lipomas of the head and neck are more common in men, especially with increasing age. Anterior neck lipomas are exceedingly rare, with only a few cases reported. Neck lipomas have been reported in the literature to masquerade as thyroid nodules.

Accurate diagnosis of a single lipoma can be made clinically in up to 85% of cases. The typical lipoma is a soft, doughy, non-tender, round, mobile mass. An anterior neck lipoma should be distinguished from the subplatysmal fat accumulation seen in the aging neck.

Figure 3. Thyroid ultrasound. Transverse image of the isthmus of the thyroid gland. The edges of the mass overlying the thyroid are indicated by the arrows. The hyperechoic (compared to muscle) echotexture with linear, echogenic lines of the mass is a typical ultrasound appearance of fat. Stephanie L. Lee

Figure 4. Gross specimen of the anterior neck mass. The cut edge of the encapsulated portion of fibrofatty tissue revealed normal appearing yellow adipose tissue. Stephanie L. Lee

Imaging is useful to confirm the diagnosis, with ultrasound in the endocrinologist’s office being a convenient method to distinguish a lipoma from thyroid tissue. On ultrasound, lipomas are hyperechoic compared to adjacent muscle and contain linear, echogenic lines (see Figure 3).

The sonographic appearance is more variable, however, than with other imaging modalities. CT scan is the study of choice. On CT scan a lipoma is seen as a homogeneous, low-attenuation fat mass that does not enhance with contrast (see Figure 2). MRI can also accurately diagnose lipomas, which have signal intensity patterns similar to subcutaneous fat.

Lesions composed of entirely homogeneous adipose tissue can be accurately distinguished from liposarcoma with CT scan or MRI. For heterogeneous tumors, which may contain a thick septum, a definitive diagnosis can only be made by histopathological examination.

Most superficial lipomas are asymptomatic and do not require treatment. If treatment is desired, complete surgical excision of the mass is most often performed.

In summary, anterior neck lipomas can rarely mimic goiters. Ultrasound and CT scan are useful to make the diagnosis and can differentiated between goiter and a subplatysmal fat pad. Surgical excision is the treatment of choice for patients with symptoms or cosmetic concerns.

Stephanie L. Lee, MD, PhD, is an Associate Chief in the Section of Endocrinology, Diabetes and Nutrition, and an Associate Professor of Medicine at Boston Medical Center.

Daniel J. Rubin, MD, is a Fellow in Endocrinology in the Section of Endocrinology, Diabetes and Nutrition at Boston Medical Center.

For more information:

• JAMA. 1985;253:1436-1437.
• J Laryngol Otol. 2006;120:47-55.
• Radiographics. 2004;24:1433-1466.