Incidental findings on single-photon emission computed tomography/computed tomography (SPECT/CT) lymphoscintigraphy in breast cancer: the proposed Westmead SPECT/CT incidental findings classification

Background The aim of this study is to determine the prevalence of incidental radiological findings detected on SPECT/CT performed as part of pre-operative lymphoscintigraphy for sentinel lymph node biopsy (SLNB) in patients undergoing breast cancer surgery and development of a modified classification to workup these lesions. Methods A retrospective audit was performed of all SPECT/CT performed in combination with lymphoscintigrams in breast cancer patients presenting with clinically node negative axillae and operated on by breast surgeons at the Westmead Breast Cancer Institute over a 12-month period. Results Four hundred and nineteen patients were included in the study. In 149 patients (35.6%), there was a total of 205 incidental findings. The most common findings were, pulmonary abnormalities (38.5%), abdominal findings (27.8%), thyroid nodules (14.6%), cardiac abnormalities (10.7%) and others (8.3%). Using our proposed Westmead SPECT/CT incidental findings (WSIF) classification, 7.8% were known, 17.6% were major findings, 48.3% were minor findings, 15.1% were minimal findings and 11.2% were equivocal findings. 17.6% (n = 36) underwent further workup and investigation and 3.4% of patients (n = 5) required therapeutic intervention, including chemotherapy for primary lung cancer(n = 1) and surgeries (thoracotomy, n = 1; thyroidectomy, n = 2; colonoscopy, n = 1). 93.8% (n = 393) had at least one SLN mapped, most commonly located in Level 1 of the axilla. Conclusion The incidental findings on SPECT/CT in combination with lymphoscintigraphy is within the range of previous studies (27.3-59.5%). A small proportion of patients required significant major interventions (3.4%). We propose that all incidental findings should be assessed according to our WSIF classification to aid in triaging need for further investigation and management.