Detailed Overview and Applications of Frozen Section in Surgical Practice
The frozen section (FS) procedure is a rapid diagnostic technique
performed during surgeries to provide real-time information about tissue
pathology. It has several critical applications that allow surgeons to make
immediate and informed decisions. Below is an exhaustive look at its
applications with detailed examples of how it is used in surgical practice.
1. Technical Process of Frozen Section
To understand the relevance of FS, it’s crucial to examine the
methodology. FS involves freezing the tissue sample to allow thin slicing
for microscopic examination. Key steps include:
Rapid Freezing: Tissue is placed in a cryostat, a machine that freezes the
sample to around -20°C. This freezing process preserves cell architecture
for quick examination.
Sectioning and Staining: A microtome within the cryostat slices the tissue
into thin sections (5-10 µm thick). The sections are stained, usually with
hematoxylin and eosin (H&E), which provides basic contrast to view
cellular structures.
Diagnosis and Reporting: Pathologists review the slide and report findings
to the surgical team, which helps guide the surgery immediately.
This entire process takes around 15-20 minutes, making it invaluable for
intraoperative decision-making.
2. Key Applications of Frozen Section in Surgical Practice with Examples
a. Oncologic Margin Assessment in Tumor Resections
FS is particularly essential in oncologic surgeries to confirm that no tumor
cells remain at the surgical margins, minimizing the risk of recurrence.
Example in Breast Cancer: During breast-conserving surgeries
(lumpectomies), FS helps assess the excised margin to confirm it is free of
cancer cells. If the margins are positive, meaning tumor cells are found at
the edge, the surgeon can excise additional tissue to achieve clear
margins.
Example in Head and Neck Cancer: Head and neck squamous cell
carcinoma often has irregular borders and can spread microscopically. FS
allows for margin assessment in real-time, so the surgeon can extend the
resection if necessary. This reduces recurrence risks, especially in
anatomically complex areas like the oral cavity or pharynx.
b. Lymph Node Evaluation for Metastasis
FS is crucial in evaluating lymph nodes to determine if a primary tumor
has spread, which informs staging and subsequent treatment.
Example in Breast Cancer: In sentinel lymph node biopsy (SLNB) for breast
cancer, the first lymph node draining the tumor site is excised and
examined by FS. If the node shows metastatic disease, the surgeon may
proceed with a full axillary lymph node dissection. If negative, further
lymphadenectomy may be avoided.
Example in Gastric Cancer: In gastric cancer surgery, FS can assess
perigastric lymph nodes. If FS identifies metastatic involvement, this may
alter the extent of nodal dissection or affect postoperative treatment
planning.
c. Intraoperative Diagnosis of Unknown or Uncertain Lesions
FS is useful when the nature of a lesion is uncertain, and determining
benignity or malignancy is necessary to decide the surgical approach.
Example in Central Nervous System (CNS) Tumors: FS is often used in
brain tumor surgeries to differentiate between gliomas and metastatic
lesions. The diagnosis affects the extent of resection, as gliomas might be
resected more extensively, whereas metastases may not require as
radical resection.
Example in Ovarian Tumors: During ovarian tumor resections, FS helps
determine if the tumor is benign, borderline, or malignant. For example, in
a suspected mucinous tumor, distinguishing a benign mucinous
cystadenoma from a malignant mucinous carcinoma affects the extent of
surgery. A benign tumor might allow for ovarian preservation, while
malignancy necessitates a more aggressive approach.
d. Assessment of Tissue Adequacy for Diagnosis
Sometimes, surgeons require confirmation that an adequate sample has
been taken, especially when biopsying deep-seated lesions.
Example in Pancreatic Lesions: For pancreatic masses, FS can confirm if
the biopsy sample contains sufficient pancreatic tissue, enabling
pathologists to make a definitive diagnosis. This is crucial in differentiating
between chronic pancreatitis and pancreatic adenocarcinoma, as the
latter requires a more aggressive resection.
Example in Musculoskeletal Tumors: In bone or soft tissue tumors, FS can
verify that a representative area of the lesion has been sampled, which is
important for sarcomas where extensive sampling is necessary to capture
high-grade areas.
e. Evaluation of Synchronous Lesions or Unexpected Findings
FS can be employed to evaluate lesions found unexpectedly during
surgery, ensuring appropriate treatment of all disease sites.
Example in Endometrial Cancer: In surgeries for endometrial cancer, FS
may be used if an unexpected ovarian mass is detected. This helps
determine if the mass is metastatic, which could prompt additional
surgical steps.
Example in Colorectal Cancer: During colorectal resections, if an
unexpected liver lesion is found, FS can assess for metastasis. If positive,
the surgeon may consider a more extensive resection or planning for
adjuvant therapy.
f. Determining Tumor Grade for Surgical Guidance
While grading is typically done postoperatively, FS may help provide a
preliminary tumor grade that can impact the immediate surgical plan.
Example in Endometrial Cancer: The preliminary grade of an endometrial
tumor affects the decision to proceed with pelvic lymphadenectomy. High-
grade tumors require more extensive surgical staging, including
lymphadenectomy.
Example in Soft Tissue Sarcomas: FS can be useful in high-grade sarcomas
where extensive resection margins are essential. A preliminary grading
assessment can help surgeons decide whether to perform wide local
excision or a more conservative resection.
g. Verification of Organ Origin in Ambiguous Cases
FS is useful for determining the tissue origin of small, ambiguous
specimens when surgical anatomy is uncertain.
Example in Parathyroid Surgery: Parathyroid glands can be small and
challenging to identify. FS can confirm parathyroid tissue, avoiding
unnecessary removal of other structures.
Example in Thyroid Surgery: In cases where a small mass is located near
the thyroid, FS can determine if it is of thyroid origin, parathyroid, or
lymph node, which directs the surgical approach accordingly.
3. Challenges and Limitations in Frozen Section Analysis
Although FS is invaluable, it has limitations that can impact its accuracy:
a. Technical Artifacts
Freezing Artifacts: Ice crystals can distort cellular morphology,
complicating the interpretation of subtle features. This is especially
problematic in fatty tissues, where freezing artifacts are common.
Thick Sections: Cryostat sections are generally thicker than formalin-fixed,
paraffin-embedded sections, which can obscure finer nuclear details
essential for grading or identifying low-grade dysplasia.
b. Sampling Errors
Focal Lesions: In cases where a lesion has a mix of benign and malignant
areas (e.g., certain sarcomas or ovarian teratomas), limited sampling
during FS can miss malignant components.
Necrotic Tumors: For large tumors with necrotic centers, viable tumor
regions must be carefully selected, or FS may yield a non-diagnostic
sample.
c. Diagnostic Limitations in Specific Tumors
Follicular Thyroid Lesions: Follicular neoplasms are challenging to
diagnose on FS due to the need to evaluate capsular or vascular invasion,
which is better assessed in permanent sections.
Pancreatic and Bile Duct Lesions: Differentiating chronic pancreatitis from
pancreatic adenocarcinoma is complex due to similar fibrotic responses.
Misinterpretation can occur, impacting surgical choices.
4. Accuracy and Reliability of Frozen Section
Frozen section has a high accuracy rate in experienced settings, with
reported rates often between 92-98%:
Breast Cancer Margin Assessment: FS for breast margin assessment has
shown accuracy rates around 95%. However, positive margins on FS can
still result in re-excisions due to the complex nature of breast tissue
architecture.
Gynecological Tumors: FS accuracy in ovarian tumors is approximately
98.5% for malignancy, but it drops to around 78.6% for borderline tumors
due to subtle cellular features that are more challenging to assess(Frozen
section).
5. Conclusion: The Clinical Relevance of Frozen Section in Surgery
The frozen section technique is integral to modern surgical pathology,
aiding in real-time, intraoperative decision-making. Its ability to provide
rapid diagnostic insights, assess margins, and stage disease enables
surgeons to tailor operations to individual patient needs. However, FS is
not a substitute for permanent sections; limitations such as artifacts,
sampling errors, and diagnostic complexity in certain tumors must be
acknowledged. Effective use of FS requires close communication between
the pathologist and surgeon to optimize patient outcomes and avoid
unnecessary surgeries.
