Lymphadenoma

Related Cases: HP-0310

The Key Features

  • Benign salivary gland tumor with epithelial and reactive lymphoid components;

  • Most tumors show sebaceous differentiation;

  • Luminal cells in tubuloglandular structures positive for CK7 but negative for CK20;

  • No association with HPV, EBV or HHV8;

  • Has to be separated from metastatic carcinoma.

  Clinical Futures

  • Typically occurs in the adults as painless mass of long duration in the parotid gland;

  • Most patients over the age of 50 years (84%), with a slight male preponderance (1.31);

  • Two thirds show some sebaceous differentiation, and one third of tumors lack sebaceous differentiation;

  • About 48% of patients have additional co-morbidities, including immunomodulatory drug therapy for autoimmune diseases and/or chemotherapy for cancers (30%) , or had associated low-grade malignancies;

  • No association with HPV, EBV, or HHV-8.

  Gross Findings

  • Well circumscribed with a median size of 2.2 cm; most (84%) tumors encapsulated

  • Cut surface: mostly homogenous, multicystic, gray-tan to yellow;

  • Cyst contents: gelatinous, yellow sebum like, chalky white, or not specified.

  Microscopic Findings

  • Sebaceous Lymphadenoma:

    • Epithelial component: solid nests, trabeculae, cords, glands, and tubules of basal, glandular, squamous, and sebaceous cells;

    • Presence of basal cell layer at the periphery;

    • Solid or cystic centers;

    •  Tubuloglandular structures with two cell layers, an outer basal cell layer and an inner luminal glandular cell layer comprising cuboidal or low columnar cells;

    • Frequent keratinization in squamous cells;

    • Cyst contents: keratinous material, eosinophilic proteinaceous fluid, or sebaceous secretions.

  • Non-Sebaceous Lymphadenoma

    • Epithelial component: predominantly solid cords and trabeculae of basal cells admixed with low columnar cells around tubuloglandular spaces without any sebaceous differentiation;

    • Squamous differentiation with keratinization not frequent.

  • Lymphocytic Infiltrate:

    •  Mixed B-cells and T-cells lymphocytes

    • Reactive germinal centers note in most cases (84%)

    • Stromal foreign body type giant cell granulomatous reaction,  frequently noted in association with ruptured cyst in sebaceous LAD (50%), and less frequently in non-sebaceous tumors;

    •  Intraepithelial B and T lymphocytes noted in most cases, but usually not remarkable.

  Immunohistochemistry Staining

  • Basal cells: Positive for p63, CK5/6, and high molecular weight keratin

  • In tubuloglandular structures, luminal cells positive for CK7 but negative for CK20;

  • Most cases (63%) negative for myoepithelial markers (calponin, smooth muscle actin, smooth muscle myosin, and S100 protein);

  • No detection of HPV, EBV, and HHV-8.

  Differential Diagnosis

  • The tumor is often well-demarcated with a capsule, which can mimic metastatic adenocarcinoma or squamous cell carcinoma in the lymph node with the present of irregular nests of tumor cells. However, the lack of significant cytologic atypia and presence of basal layers navigate away from a malignany.

  Treatment and Prognosis

  • Rare cases may undergo malignant transformation.

  Reference

  • Modern Pathology (2012) 25, 2635

  • Oncology Letters 7: 1097-1101, 2014

Last update: 01/25/2016