Benign lymphoepithelial lesions

Benign lymphoepithelial lesions (BLL or BLEL), also misleadingly known as AIDS-related parotid cysts (ARPC), are mixed solid and cystic lesions that enlarge the parotid glands, and are usually associated with cervical lymph node enlargement, and nasopharyngeal lymphofollicular hyperplasia.

Epidemiology

Despite their aforementioned alternative name, BLL are seen usually in HIV positive patients without AIDS, and are not an AIDS defining illness. It is relatively common in the HIV population, with 5% of patients eventually developing BLL.

Pathology

Thought to arise from dilatation of intraglandular ducts from obstruction due to lymphoid hypertrophy. They are bilateral in ~20% of cases. 

Location

BLLs most commonly arise in the parotid gland, and are only rarely seen in the submandibular glands or sublingual glands.

Radiographic features

  • well circumscribed cystic spaces
  • may demonstrate thin rim enhancement on post contrast MRI
  • ultrasound demonstrates these 'cystic' lesions to actually have multiple small septations, and commonly also small mural nodules (40%)
  • a vascular pedicle may be seen entering the cystic region

BLLs are usually seen associated with other sites of lymphoid hyperplasia 4, including:

  • prominent nasopharyngeal adenoidal tissue: seen in 35% of HIV positive patients 4
  • posterior triangle lymphadenopathy
  • abnormal bone marrow signal

Differential diagnosis

See also

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