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Cat‐scratch disease (CSD) is a granulomatous lymphadenitis that most commonly results from cutaneous inoculation caused by a scratch from a domestic cat. The causative microorganism is Bartonella henselae, a Gram negative bacillus. Approximately 90% of patients who have cat‐scratch disease have a history of exposure to cats, and 75% of these patients report a cat scratch or bite (Arrieta and McCaffrey 2005). Dogs have been implicated in 5% in these cases. This disease process begins in the preauricular and cervical lymph nodes as a chronic lymphadenitis and may ultimately involve the salivary glands, most commonly the parotid gland by contiguous spread (English et al. 1988).

Figure 3.15. A 52‐year‐old man (a) with a one‐year history of vague discomfort in the left upper neck. Screening panoramic radiograph (b) showed no evidence of a sialolith. His diagnosis was chronic submandibular sialadenitis and he was prepared for left submandibular gland excision (c). The surgery was carried through anatomic planes, including the investing layer of the deep cervical fascia (d). The dissection is carried deep to this layer since a cancer surgery is not being performed that would require a dissection superficial to the investing fascia. Exposure of the gland demonstrates a small submandibular gland due to scar contracture (e). Inferior retraction of the gland allows for identification and preservation of the lingual nerve (f). The specimen (g) is bivalved (h), which allows for the appreciation of scar within the gland. The resultant tissue bed (i) shows the hypoglossal nerve, which is routinely preserved in excision of the submandibular gland. Histopathology shows a sclerosing sialadenitis (j). The patient's symptoms were eliminated postoperatively, and he healed uneventfully, as noted at one year following the surgery (k).

The diagnosis of CSD has changed with advances in serologic and molecular biologic techniques. These methods have replaced the need for the Rose Hanger skin test previously used to establish the diagnosis of CSD. Testing for the presence of antibodies to B. henselae is now the most commonly used test to confirm the diagnosis. The two methods used for antibody detection are the indirect fluorescent antibody (IFA) and the enzyme immunoassay (EIA). When tissue is removed for diagnosis, histologic examination might demonstrate bacilli with the use of Warthin–Starry staining or a Steiner stain. Lymph node involvement shows reticular cell hyperplasia, granuloma formation, and occasionally a stellate abscess.

In most cases, no active therapy is required. The patient should be reassured that the lymphadenopathy is self‐limited and will spontaneously resolve in two to four months. Antibiotic therapy is indicated when patients are symptomatic. Antibiotics reported to be most effective include rifampin, erythromycin, gentamycin, azithromycin, and ciprofloxacin. Surgery becomes necessary when the diagnosis is equivocal, or when incision and drainage is indicated (Figure 3.16).