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 49-year-old woman presented with arm pain for five days. The pain was located in the right armpit and sensitive to touch. The patient also reported bilateral ear pain. There were no chills, fevers, or night sweats. The patient had a normal screening mammogram five months prior. Her family history was significant for her mother with breast cancer and her father with gastric cancer. Socially, she had two cats. On physical examination, there was a painful mass below the right armpit with no overlying skin lesions. Because of the location of the mass and the family history of breast cancer, a repeat mammogram and an ultrasound were recommended. The imaging results were remarkable for a morphologically abnormal right axillary lymph node measuring 31 mm in diameter (Figure ). Ultrasound-guided biopsy was performed, and the surgical pathology exam results were consistent with cat scratch lymphadenopathy. Flow cytometry revealed no detectable monoclonal B cells or immunophenotypically aberrant T cells, which diminished the concern for malignancy. Serology was not available for this case.