This post is an answer to the Case – A Painless Lump in the Neck
What is the likely diagnosis?
This has the typical features of a branchial cyst.
Theories of its etiology
- The embryological hypothesis. In the development of the side of the neck, the second branchial arch of the fetus grows down over the third and fourth arches to form the cervical sinus. Normally, this sinus disappears before birth. It is postulated that its persistence leads to the formation of a branchial cyst. There is little doubt that this accounts for the rather uncommon branchial fistula – a track that is present at birth, opens in front of the origin of sternocleidomastoid above the sternoclavicular joint, and tracks upwards almost to the level of the palatine tonsil.
- The cervical lymph node theory. The cervical lymph nodes, on histological examination, are often found to contain rests of stratified squamous epithelium. One of these rests is postulated to break down into a cystic space – hence the squamous lining of the cyst. The fact that the cyst may enlarge after a throat infection – as happened in this case – supports this theory.
What does the fluid inside the cyst look like to the naked eye and what is its microscopic appearance?
The fluid is thick, turbid, yellowish white and looks just like pus. However, under the microscope, it is seen to contain typical cholesterol crystals. This woman’s cyst was indeed aspirated in the clinic, to confirm the diagnosis.
What may complicate this condition?
The cyst may become infected, producing an abscess, which requires surgical drainage followed by a rather difficult removal of the now adherent cyst wall to prevent further infections.
Are there any other diagnoses you might have to consider?
A tuberculous lymph node or, if infected, an acute cervical lymphadenitis.
What treatment do you think was advised in this case?
Elective surgical excision of the cyst, first to obviate the risk of infection and second because the patient was now anxious to get rid of her rather unsightly lump. This was duly carried out as a day case.
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