Histology · Year 1 · from Histology
Case 1: Intraoperative Frozen Section for Breast Mass
Clinical Presentation
A 54-year-old woman presents with a 2.5 cm palpable mass in her right breast discovered during self-examination. Mammography reveals an irregular, spiculated mass suspicious for malignancy (BI-RADS 5). Core needle biopsy confirms invasive ductal carcinoma. She is scheduled for lumpectomy with sentinel lymph node biopsy.
During surgery, the surgeon requests intraoperative frozen section consultation on the sentinel lymph node and surgical margins.
Clinical History
- Post-menopausal female, last menstrual period 4 years ago
- No family history of breast cancer
- No prior breast biopsies
- Core biopsy: Grade 2 invasive ductal carcinoma, ER+, PR+, HER2-
The Histology Question
The pathologist receives fresh tissue in the operating room:
- Sentinel lymph node: 1.2 cm lymph node, grossly unremarkable
- Superior margin: 0.3 cm rim of tissue
The tissue is rapidly frozen in OCT compound at -20C, sectioned at 5 micrometers on the cryostat, and stained with H&E. Results must be communicated to the surgeon within 20 minutes.
Frozen Section Findings
Sentinel Lymph Node: Sections show lymph node with preserved architecture. A focus of atypical epithelial cells is identified in the subcapsular sinus, suspicious for metastatic carcinoma. The cells are cohesive, have enlarged nuclei with prominent nucleoli, and appear foreign to the lymph node architecture.
Superior Margin: Sections show fibroadipose tissue with adjacent breast parenchyma. No tumor is identified within 2 mm of the inked margin.
Image: Invasive breast carcinoma, H&E stain. Note the irregular nests of tumor cells with hyperchromatic nuclei infiltrating the desmoplastic stroma. This histological pattern guides intraoperative decision-making.
Image source: Wikimedia Commons, Public Domain
Intraoperative Report
The pathologist calls the operating room:
- "Sentinel lymph node: POSITIVE for metastatic carcinoma, single focus in subcapsular sinus"
- "Superior margin: NEGATIVE for carcinoma"
Surgical Decision
Based on this information, the surgeon:
- Proceeds with axillary lymph node dissection due to positive sentinel node
- Does not require re-excision of superior margin
Final Permanent Section Diagnosis
After routine formalin fixation and paraffin embedding (24-48 hours later):
- Sentinel lymph node: Metastatic ductal carcinoma, 3 mm focus (confirmed)
- Superior margin: Negative, closest margin 3 mm (confirmed)
- Additional immunohistochemistry on tumor: Cytokeratin AE1/AE3 positive, confirming epithelial origin
Learning Points
- Frozen sections provide rapid intraoperative diagnosis - Results in ~20 minutes guide immediate surgical decisions
- Tissue processing differences:
- Frozen section: Fresh tissue frozen, sectioned at -20C, rapid H&E stain
- Permanent section: Fixed in formalin, dehydrated, embedded in paraffin, higher quality
- Frozen section limitations:
- Lower tissue quality than permanent sections
- Freezing artifact can obscure cellular details
- Small lesions may be missed (sampling error)
- Some diagnoses should be deferred (e.g., lymphoma subtyping)
- When frozen section is appropriate:
- Margin evaluation during cancer surgery
- Sentinel lymph node assessment
- Tissue identification (parathyroid vs. lymph node)
- Confirming adequate tissue sampling
- Histological interpretation relies on fundamental principles:
- Tissue architecture (preserved vs. disrupted)
- Cell morphology (normal vs. atypical)
- Staining patterns (basophilic nuclei, eosinophilic cytoplasm)
Discussion Questions
- Why is frozen section quality inferior to permanent sections?
- What artifacts might you expect to see in frozen sections?
- In what circumstances should a pathologist defer diagnosis to permanent sections?
- How does understanding normal histological architecture help identify pathology?