What are the possible causes and recommended work‑up and treatment for a dorsocervical fat pad (buffalo hump) at the base of the neck?

Dorsocervical Fat Pad (Buffalo Hump): Causes, Work-Up, and Treatment

Primary Differential Diagnosis

The most critical first step is to rule out Cushing syndrome and malignancy, as these directly impact mortality and require urgent intervention.

Endocrine Causes (Highest Priority)

• Cushing syndrome presents with dorsocervical fat accumulation ("buffalo hump") alongside centripetal obesity, proximal muscle weakness, hypertension, purple striae, supraclavicular fat pad enlargement, hyperglycemia, and hypokalemia—this constellation mandates immediate endocrine evaluation 1
• Adrenocortical carcinoma, though rare (1–2 per million incidence), can cause Cushing syndrome with hypersecretion of cortisol and must be excluded in any patient with buffalo hump and other stigmata of cortisol excess 1

HIV-Associated Lipodystrophy

• Dorsocervical lipomatosis occurs in 1–2% of HIV patients, representing regional fat accumulation that is not due to hypercortisolism—24-hour urinary free cortisol and dexamethasone suppression tests are normal in these patients 2
• This can occur with or without protease inhibitor therapy, suggesting the mechanism involves regional abnormalities in lipogenesis and lipolysis related to HIV infection itself 2

Metabolic/Insulin Resistance

• When a dorsocervical fat pad appears in the context of obesity, it may signal underlying insulin resistance with dyslipidemia (elevated triglycerides, increased LDL, reduced HDL) 3

Mandatory Initial Work-Up

Step 1: Screen for Cushing Syndrome

• Measure 24-hour urinary free cortisol excretion as the initial screening test 2
• Perform overnight low-dose dexamethasone suppression test (1 mg at bedtime, measure morning cortisol; normal suppression is <83 nmol/L or <3 μg/dL) 2
• If either test is abnormal, measure plasma cortisol every 4 hours for 24 hours to assess circadian rhythm—loss of the normal nadir at midnight suggests Cushing syndrome 2

Step 2: Metabolic Assessment

• Fasting plasma glucose followed by 2-hour oral glucose tolerance test (75 g glucose load) to detect insulin resistance, pre-diabetes, or diabetes 3
• Fasting lipid panel to identify the dyslipidemic pattern associated with metabolic syndrome 3
• Thyroid-stimulating hormone (TSH) to exclude thyroid disease as a contributing factor 3

Step 3: HIV Testing

• HIV serology is mandatory in any patient with dorsocervical fat pad without clear Cushing syndrome, given the 1–2% prevalence of buffalo hump in HIV-positive patients 4, 2

Step 4: Imaging When Cushing Syndrome Is Confirmed

• If biochemical testing confirms hypercortisolism, obtain contrast-enhanced CT of the abdomen to evaluate for adrenal masses, as adrenocortical carcinoma requires open adrenalectomy (not laparoscopic) due to rupture risk 1

Critical Pitfalls to Avoid

• Do not assume buffalo hump equals Cushing syndrome—HIV-associated lipodystrophy and metabolic syndrome can produce identical physical findings without hypercortisolism 2
• Do not rely on physical examination alone—dorsocervical fat accumulation in HIV patients shows normal cortisol dynamics and normal dexamethasone suppression despite the prominent hump 2
• Do not skip the oral glucose tolerance test—fasting glucose alone misses early glucose intolerance in patients with insulin resistance 3

Treatment Algorithm

If Cushing Syndrome Is Confirmed

• Refer immediately to endocrinology and surgical oncology for definitive management of the underlying cause (adrenal tumor, pituitary adenoma, ectopic ACTH) 1
• Surgical resection of adrenocortical carcinoma via open adrenalectomy is the definitive treatment when the tumor is the source of cortisol excess 1

If HIV-Associated Lipodystrophy

• Liposuction is the only effective treatment for dorsocervical fat pad in HIV patients, as no definitive medical therapy exists 4
• Dissector-assisted liposuction offers superior outcomes by pre-dissecting fibrous tissue, reducing resistance, and minimizing trauma—57 patients treated with this technique showed significant improvement at 6 months without complications 5
• Traditional lipectomy causes significant scarring and prolonged recovery, making it less favorable than modern liposuction techniques 5

If Metabolic Syndrome/Insulin Resistance

• Weight reduction of 7–10% of excess body weight is the most effective strategy for obesity-associated dorsocervical fat accumulation 3
• Treat underlying conditions such as polycystic ovary syndrome with hormonal therapy and insulin-sensitizing agents 3
• Address cardiovascular risk aggressively, as patients with insulin resistance and dorsocervical fat carry markedly increased cardiovascular disease risk due to accompanying dyslipidemia 3

Surgical Considerations for Cosmetic Improvement

• For patients with dorsocervical fat pad causing significant aesthetic or functional impairment, liposuction using a 3.5mm harvesting cannula with cutting edge after fibrous tissue dissection provides excellent outcomes 5
• The average volume of buffalo hump treated surgically is approximately 329 mL, and immediate improvements in appearance are observed in all patients 5
• Liposuction is appropriate for patients with dorsocervical fat pad from any cause once life-threatening etiologies (Cushing syndrome, malignancy) are excluded 5, 6