{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T05:14:38Z","timestamp":1783401278996,"version":"3.54.6"},"reference-count":22,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,7,7]],"date-time":"2026-07-07T00:00:00Z","timestamp":1783382400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Oncol."],"abstract":"<jats:sec>\n                    <jats:title>Background<\/jats:title>\n                    <jats:p>Apocrine encapsulated papillary carcinoma (A-EPC) of the breast is exceedingly rare, having been described primarily through sporadic case reports prior to 2022 (typically fewer than 10 cumulative cases per report). The largest series to date \u2014 28 cases from a single centre \u2014 was recently published in 2026. Whether breast-conserving surgery (BCS) is appropriate for A-EPC with frank invasion, and how the recent Rakha\u2013Quinn (2025) staging criteria should be applied, remain unresolved.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Case presentation<\/jats:title>\n                    <jats:p>A 57-year-old postmenopausal woman presented with a 5-month history of an enlarging right breast mass. Imaging demonstrated a 27 \u00d7 17 \u00d7 17\u00a0mm well-circumscribed nodule at the 9 o\u2019clock position, approximately 2\u00a0cm lateral to the nipple. Intraoperative frozen section identified prominent apocrine cytological features, predicting a hormone-receptor-negative phenotype; same-session sentinel lymph node biopsy (SLNB) was therefore performed during the index operation. Successful BCS with negative margins was achieved. Final histopathology demonstrated A-EPC (2.3 \u00d7 1.8 \u00d7 1.5\u00a0cm) with microscopic multifocal frank invasion (largest focus 4\u00a0mm; pT1aN0M0; 0\/4 sentinel nodes). Immunohistochemistry confirmed ER\u2212\/PR\u2212\/HER2 2+ (FISH-negative)\/AR+ (~90%)\/GCDFP-15+\/Ki-67 ~15%. A PIK3CA exon 20 H1047R\/L hotspot mutation was detected. After multidisciplinary discussion, no systemic therapy was administered and the patient completed adjuvant whole-breast radiotherapy.<\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusions<\/jats:title>\n                    <jats:p>Three points were central to this case: intraoperative frozen-section recognition of apocrine differentiation supported same-session SLNB during breast-conserving surgery; systematic application of the Rakha\u2013Quinn (2025) staging criteria \u2014 including the 5\u00a0mm proximity rule and the assessment of whether microscopic multifocal invasion indicates a diffusely invasive EPC-like pattern \u2014 supported staging as pT1a; and the co-occurrence of strong androgen-receptor positivity and a PIK3CA mutation provides a rationale for AR-PI3K dual-pathway targeted therapy should recurrence occur.<\/jats:p>\n                  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