Definition: Atypical lymphadenopathies fail to achieve the morphologic criteria of a malignant neoplasm, but exceed the usual concepts of follicular, lymphoid, or sinus histiocytic hyperplasias. Rich cellular proliferations usually composed of prominent histiocytes, or immunoblasts, or both with or without a vascular scaffolding obscure the nodal architecture.

Etiology

 infectious lymphadenitis

• nodal toxoplasmosis
• nodal infectious mononucleosis
• nodal zoster
• vaccination-induced lymphadenopathies

 dermatopathic lymphadenitis (associated with cutaneous disease)
 anticonvulsant pseudolymphoma

• hypersensitivity to anticonvulsants (usually phenytoin),

 Chediak-Higashi syndrome
 sinus histiocytosis with massive lymphadenopathy
 giant lymph node hyperplasia
 angioimmunoblastic lymphadenopathy
 nodal Kawasaki disease (mucocutaneous lymph node syndrome)

 nodal histiocytoses

• acute disseminated histiocytosis

See also

 lymph nodes

• adenitis
• lymphadenopathies