Benign solitary neurilemoma (Schwannoma). A correlative cytological and histological study of 28 cases.

A correlative histological and cytological study of 28 cases of solitary neurilemoma is presented. The typical histological mixture of Antoni type A and B tissue correlated well with the cytological findings. In the smears, the Antoni type A tissue was represented by tissue fragments with a fibrillar ground substance and slender, spindle-shaped cells forming obvious Verocay bodies in 24 cases, and the Antoni type B tissue by loose, microcystic fragments with single, elongated nuclei sometimes looking like fish-hooks and with indistinct, slender, cytoplasmic processes. The ancient neurilemomas, a variant of the ordinary neurilemomas, in this series were characterised both histologically and cytologically by nuclear hyperchromasia and polymorphism, which it is important to be aware of in order to avoid an erroneous diagnosis of sarcoma or probable sarcoma. The differential diagnosis is discussed and it is concluded that diagnosis of neurilemoma by fine-needle aspiration biopsy is possible, particularly when Verocay bodies and/or a fibrillar ground substance are present in the smears. It is stressed that fine-needle aspiration biopsy is an important aid to pre-operative diagnosis of neurilemoma, and thus to planning of the operative treatment.