A 35-year-old BRCA1-positive woman elects for risk-reducing salpingo-oophorectomy (RRSO). Pathological examination of the fallopian tube using the SEE-FIM (sectioning and extensively examining the fimbriated end) protocol reveals a serous tubal intraepithelial carcinoma (STIC) at the fimbria. This finding is clinically significant because:
- A STIC is a precursor of mucinous ovarian carcinoma and warrants hysterectomy
- B STIC represents metastatic spread from an endometrial serous carcinoma — requiring endometrial sampling
- C STIC at the fimbriated end is now considered the origin of most high-grade serous carcinomas of the ovary, peritoneum, and fallopian tube — necessitating staging and adjuvant platinum-taxane chemotherapy ✓
- D STIC is a benign reactive change in BRCA1 carriers with no malignant potential
Explanation
The current paradigm for high-grade serous carcinoma (HGSC) pathogenesis is that most cases originate from the fimbriated end of the fallopian tube as STIC — a p53-signature → STIC → HGSC progression. STICs show TP53 mutations, BRCA1/2 dysfunction, MIB-1 (Ki-67) >10%, and loss of PAX2 expression, identical to the associated invasive HGSC. Discovery of STIC on RRSO specimen in a BRCA1 carrier warrants: full surgical staging, abdominal washing for cytology, and omentum biopsy. If occult invasive carcinoma is excluded and STIC is confined, most guidelines recommend carboplatin-paclitaxel adjuvant chemotherapy given the risk of peritoneal spread.
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
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Written and medically reviewed by the StethoPrep medical team.