Part 2
History
A 67-year-old man presented with a palpable lump in the left axillary tail for 2 weeks. There was no associated fever, chills, or overlying redness. Diagnostic left breast mammography and ultrasound were performed for further assessment of the palpable lump (Figure 1).
67-year-old man with a palpable lump in the axillary tail of the left breast. A: Diagnostic left breast mediolateral oblique mammogram with a BB marker in the region of the palpable area demonstrates an asymmetry (long arrow) in the upper posterior breast anteriorly, and an adjacent enlarged left axillary lymph node posteriorly (short arrow). Radial (B) and antiradial (C) ultrasound images of the left axilla in the palpable area demonstrate an irregular hypoechoic mass with increased vascularity measuring 2.1 × 1.7 × 1.2 cm (long arrow), and an adjacent enlarged left axillary lymph node with diffuse cortical thickening (short arrow). D: Post clip left breast mediolateral mammogram depicting a Q clip (arrow) within an asymmetry, corresponding to the biopsied mass.
Diagnosis: Bartonella (cat scratch disease)
On mammography, there was a focal asymmetry in the upper outer left breast corresponding to the palpable area (Figure 1A). Ultrasound of the targeted site showed an irregular hypoechoic mass in the left axillary tail (Figures 1B and C) with lymphadenopathy. Ultrasound-guided biopsy of the mass revealed soft tan-yellow tissue with necrotizing granulomatous inflammation. A Warthin-Starry stain showed rod-shaped bacilli consistent with Bartonella henselae. Acid fast bacilli and Gram stain testing showed no evidence of acid fast bacilli or fungal elements.
The differential diagnosis of the imaging findings includes breast cancer, abscess, sarcoma, lymphoma, and chronic granulomatous inflammation. Abscess is a less likely differential diagnosis because the patient presented with no systemic symptoms such as fever, chills, malaise, overlying warmth, or redness. Also, there was no prior history of surgery at that site, making scar or fibrosis less likely. The patient had adopted a kitten 2 months before the onset of symptoms.
This case is an unusual presentation of cat scratch disease, which typically presents as benign regional lymphadenitis resulting from a scratch or a bite in the distal upper extremity (1). It most commonly affects children and adolescents, with a peak reported in patients aged between 2 and 14 years (2). The lymphadenopathy usually occurs 1–3 weeks after inoculation and may persist for several months after other local symptoms have subsided. The condition is self-limited, with most cases resolving within 1 month, with or without treatment (3). Breast parenchymal involvement is much less likely, typically presenting as a palpable lump with enlarged axillary lymph nodes (3). A definite diagnosis is based on polymerase chain reaction for DNA analysis or serologic testing, because isolating Bartonella species in culture is a difficult process, and histologic examination usually shows nonspecific features such as granulomas (4, 5).
This patient’s presentation is rare, given his age, the presenting symptoms, and the uncommon imaging findings. The patient tested positive for Bartonella IgG antibodies, and symptoms subsided after a short course of azithromycin.
Conflict of interest statement
None declared.
References
