Where is imprint cytology (cytologic examination of tissue imprints) most commonly used?

Imprint Cytology: Primary Clinical Applications

Imprint cytology is most commonly used for intraoperative assessment of sentinel lymph nodes in breast cancer and for rapid evaluation during brain tumor surgery. 1

Primary Clinical Settings

Sentinel Lymph Node Evaluation in Breast Cancer

Breast cancer sentinel lymph node biopsy represents the predominant application of imprint cytology in modern surgical practice. 1, 2

• Imprint cytology allows immediate intraoperative assessment of sentinel lymph nodes (SLNs) by touching cut nodal surfaces to glass slides, providing cellular imprints that can be rapidly evaluated 1
• The technique achieves sensitivity of 90.9-96.0%, specificity of 97.8-100%, and overall accuracy of 92.1-98.36% for detecting nodal metastases 3, 4
• A positive imprint provides immediate practical assistance for surgical decision-making, though negative imprints are not definitive evidence that a node is tumor-free 1

The American Society of Clinical Oncology guidelines explicitly recognize imprint cytology as a legitimate intraoperative assessment method, noting it can detect micrometastases more accurately than conventional frozen section analysis 1, 3. However, approximately 8-9 false-negative results occur per 100 patients evaluated, meaning disease will not be detected intraoperatively in roughly one-third to one-half of patients with metastatic nodes 1, 5.

Brain Tumor Intraoperative Consultation

Touch (imprint) cytology should be used on all brain tissue samples during neurosurgical procedures, regardless of size or type. 1, 2

• Imprint preparations excel at detecting processes with cellular dyscohesion including inflammatory processes, hematologic processes, pituitary adenomas, germinomas, small round blue cell tumors, and metastatic tumors (especially melanoma) 1
• Touch/drag preparations provide particular utility for necrotic or hemorrhagic tissue when attempting to sample for rare tumor cells 1
• The technique provides excellent cellular detail superior to frozen sections, with no freezing artifacts, and delivers extremely rapid results using Diff-Quik staining 1, 2

The College of American Pathologists emphasizes that cytology can be performed on even the tiniest brain tissue samples that could easily be lost during frozen section preparation 1.

Secondary Applications

Oral/Oropharyngeal Squamous Cell Carcinoma

• Imprint cytology has been described for sentinel lymph node assessment in oral squamous cell carcinoma (OSCC), with one study demonstrating high sensitivity and specificity in 30 cases 1
• The technique has an advantage over frozen section evaluation in that no tissue is lost during sample generation 1
• However, recent studies show frozen section evaluation may be more accurate for intraoperative diagnosis in this setting, and much larger studies are required before widespread adoption 1

General Surgical Pathology

• Imprint cytology achieves 94.3% accuracy across diverse surgical specimens from all organs, with 97.5% accuracy for benign lesions and 91% for malignant lesions 6
• When combined with frozen section, the diagnostic yield reaches 99% 6
• The false-negative rate is 1.3% with no false-positive results reported 6

Critical Limitations and Pitfalls

Negative imprint cytology results should never be interpreted as definitive evidence of tumor-free tissue; suspicious findings must be deferred to permanent paraffin sections. 1

• Sampling limitations and the challenge of detecting micrometastases result in false-negative rates of 38.2-50.8% in certain populations, particularly after neoadjuvant chemotherapy 7, 8
• Patients with micrometastases or isolated tumor cells have 2.3 times higher risk of false-negative imprint cytology results compared to macrometastases 7
• In breast cancer patients initially node-negative (N0) who received neoadjuvant chemotherapy, imprint cytology is positive in only 5-9.6% of cases, questioning its utility in this specific population 8

Optimal Practice Integration

Multiple cytology preparation types should be routinely employed on each specimen to provide complementary diagnostic information. 2

• Pairing touch/imprint preparations with smear/squash preparations maximizes diagnostic yield 1, 2
• Air-dried smears with Diff-Quik staining and alcohol-fixed smears with H&E or Papanicolaou staining represent standard protocols 2
• Cell block preparation should be performed when special studies (immunohistochemistry, flow cytometry, molecular testing) may be required 2