Cytologic diagnosis of cat scratch disease (CSD) by fine-needle aspiration

Cat scratch disease (CSD) is usually a benign, self-limited lymphadenitis, characterized by suppurative granulomas. It can, however, produce a wide spectrum of clinical symptoms and cytologic changes and be the source of diagnostic dilemmas. Identification of pleomorphic bacilli (PB) with silver impregnation stains aids in the diagnosis, but this has not been well documented in cytologic preparations or in cases without the classic morphologic changes. We reviewed 13 aspirations from eight patients (aged 13-36 yr) occurring over a 15 mo time period, all clinically or cytologically suspicious for CSD. Sites included: axilla (6), parotid (3), epitrochlear (1), neck (1), submental (1), and intraclavicular (1) nodes. Neoplasia was initially suspected clinically in 38% of the cases. All but two patients had cat exposure on subsequent interview. The cytologic differential included bacterial abscess and lymphoproliferative disorders in 31%. Neither granulomas nor suppurative inflammation were seen in all cases. Changes included: granulomas (77%), PMNs (62%), dispersed epithelioid histiocytes (46%), and suppurative granulomas (38%). A modified silver stain (Modified Steiner, Sigma Diagnostics, St. Louis, MO) was performed on all specimens. Silver positive organisms were seen in 69% of cases and were not limited to those preparations with suppurative granulomas. Fine-needle aspiration biopsy (FNAB) is an effective method for diagnosing CSD despite its heterogeneous appearance; and, when combined with clinical information and silver staining, may obviate the need for excision.