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 47-year-old woman presented with a painful, compressible, and mobile lump in the left axilla for three days without discharge or erythema. Prior to lump presentation, the patient had intermittent elbow and arm pain, lasting approximately 45 minutes. She denied fevers, chills, and night sweats. Her family history was significant for a father with liver cancer and maternal grandmother with bone cancer. She worked as a veterinarian and was a former smoker of five pack-years. On physical examination, there was a compressible, mobile, tender lump measuring 30 x 20 mm in the left axilla. Mammogram revealed normal right breast and left axillary lymphadenopathy (Figures , ). The ultrasound showed two adjacent enlarged axillary lymph nodes measuring 31 mm and 27 mm in diameter, respectively (Figure ).\nThe results from the mammogram and ultrasound supported the physical exam findings, prompting further CSD assessment with ultrasound-guided core biopsy. The biopsies showed necrotizing lymphadenitis that partially effaced the lymph node architecture. In the necrotic area, there were microabcesses with neutrophils and surrounding histiocytes, some of which were palisading (Figure ). Giant cells were scattered throughout. Staining for cluster of differentiation 20 and cluster of differentiation 3 showed some residual follicles and interfollicular T cells. Other stains including acid-fast bacilli, methenamine silver stain, toxoplasmosis, and periodic acid-Schiff were all negative. Cat scratch stain was positive. To confirm the diagnosis, serology for B. henselae was subsequently ordered with the results of abnormal B. henselae IgG titer of 1:1024, and abnormal B. henselae antibody IgM titer of 1:32.