What is the cause of lumpy growth in neck?

A 20-year-old recovering from a devastating brain abscess went to the doctor for a follow-up visit. His father went along and sat in the examining room, relieved to hear that the young man was progressing well.

Before they left, though, the physician pulled the father aside.

He could not help noticing that the older man had a lump the size of a golf ball protruding from his neck.

"How long has this been there?" he asked the man.

"A month, maybe," the man replied. "I'm not sure."

He was 53, a heavy smoker who drank a bit too much at times and worked in construction much of his life. The recession had taken his job and health insurance, and although he was qualified for Medicaid, he had not applied for coverage.

The lump did not hurt. He had no trouble swallowing. He had no fevers and seemed to be feeling fine. Still, the doctor was worried the growth was something bad, perhaps a head and neck cancer.

But because the man had no health insurance and had gone to the office as an outpatient, no tests could be obtained.

If he had been sick enough to be admitted to the hospital, the doctor might have been able to help.

"Apply for Medicaid and come back as soon as you can," the doctor said.

Three months later, the man returned with his Medicaid card. The doctor ordered a CT scan, which showed the mass was a large cystic structure about two inches across, filled with fluid the density of water.

What was it?

With the man's long history of smoking and drinking, the most likely diagnosis was cancer, although it was presenting in an unusual way.

If this were a tumor, why was it growing so slowly? And why was there so much fluid in the mass? Cancers are usually solid with little or no fluid in the center.

Could the tumor have stripped the blood supply to the central part of the mass leading to tissue death (necrosis) and subsequent liquefaction? That would be rare, but not impossible.

Or could it be an infection? TB would be on top of that list, but the patient had no fevers and no weight loss, symptoms that normally result from TB.

Then what about TB's cousin, Mycobacterium avium-intracellulare? This germ is almost always seen in patients with advanced HIV, and this patient had no risk factors nor other signs of that disease.

Perhaps, then, the man had what is commonly (if inelegantly) known as actinomycosis or "lumpy jaw."

That is caused by Actinomyces, an unusual bacterium that lives in the mouth and that can get under an unhealthy tooth and slowly make its way to the lymph nodes under the neck. But this man's teeth were perfectly healthy. And again, in the absence of fever or weight loss, an infection seemed unlikely.

In their search for a clue, the doctor ordered a fine-needle aspiration of the fluid in the mass. This relatively noninvasive biopsy is simple, not painful, and often yields the answer.

The results, however, did not provide much useful information. The fluid contained only a few polymorphonuclear leucocytes, the white blood cells that fight bacterial infections, along with bits of dead tissue.

No traces of tumor. No signs of TB.

The next step was to take the man to the operating room for a full excision of the mass.

When the head and neck surgeons opened the patient's neck, they realized the mass was thin-walled, characteristic of benign cysts.

They also found no signs of an invasion into adjacent healthy tissue, so whatever it was, it was clearly not a tumor. They suspected it was a branchial cleft cyst, which usually occur in much younger people.

The tissue went off to the pathology lab for analysis.

Word came back that the mass was, after all, a branchial cleft cyst.

Despite their alarming appearance, these cysts are totally harmless, a glitch in fetal development. In their early stages, human embryos, like fish, have tiny gill-like pouches in the neck. These rudimentary gills quickly close and disappear during the first few months of gestation. Occasionally, however, they fail to close and later in life present themselves as an expanding mass in the lateral neck.

That is what happened in this case. These cysts occasionally shrink on their own but have the potential to get infected and cause pain, redness, and fever.

Treatment is straightforward. The cysts can be aspirated to drain the fluid or they can be removed surgically.

Although it was not exactly great news for the patient to learn he had vestigial fishlike gills growing in his neck, he and his physicians were enormously relieved that the problem turned out to be so benign.

If nothing else, he will have a strong argument if he ever gets into a dinner-party debate about evolution with a creationist.