An 18-year-old male patient presented with a new, large, and tender lump under his left axilla for two weeks with associated chills, night sweats, and left thumb lesion for one week. The patient reported sleeping with his cat and experiencing a recent cat bite. His family history was significant for his grandmother with an unknown type of cancer in the axillary region. On physical examination, two tender subcutaneous nodules in the left axilla, measuring 5 cm and 1 cm in diameter, respectively, were discovered. On the left thumb, an erythematous and excoriated papule was noted. Given his clinical presentation, social history, family history, and physical examination, the differential diagnosis included lymphoma, reactive lymphadenopathy, abscess, deep epidermal inclusion cyst, and CSD. An ultrasound revealed enlarged left axillary lymph nodes with cortical thickening, measuring up to 33 mm, prompting further investigation with axillary lymph node biopsy (Figure ). On tissue examination of the biopsy, necrotizing lymphadenitis was identified, which is consistent with CSD. To confirm the diagnosis, serology for B. henselae was subsequently ordered resulting in an immunoglobulin G (IgG) titer against B. henselae of 1:256 and an immunoglobulin M (IgM) titer of >1:256. No monoclonal B-cell or abnormal T-cell populations were detected on flow cytometry.
A 58-year-old woman presented with breast and rib pain. She reported left axillary lymphadenopathy, abdominal fullness, and malaise. She denied fever and breast drainage. Her past medical history was significant for hepatitis C. Socially, she had two cats and was bitten by a cat a month prior. Review of systems was positive for fatigue and negative for appetite change, chills, diaphoresis, and fevers. Lung cancer screening CT, which was completed a day prior to this visit, showed an ill-defined mass measuring up to 3.5 cm in the left axilla. There was mild adjacent soft tissue stranding. These findings indicated an infectious, inflammatory, or malignant process. She was promptly treated with doxycycline for CSD, but also recommended to obtain a diagnostic mammogram and an ultrasound of the left axilla. The imaging showed an enlarged lymph node with an adjacent abscess, which altogether measured 30 x 17 mm in the left axilla (Figure ).\nTherefore, a lymph node biopsy and drainage of the abscess with culture were ordered. The lymph node biopsy revealed necrotizing granulomatous inflammation with the following differential diagnosis: CSD, tuberculosis, and other infectious entities. The abscess culture was negative for aerobic/anaerobic organisms and showed few polymorphonuclear leukocytes. Given her history of a cat scratch, symptoms, and pathology results, an infectious etiology was most likely. To confirm the diagnosis and rule out other causes, serology for B. henselae was ordered which showed high B. henselae IgG titer of >1:1024 and IgM titer of 1:128.