|Year : 2017 | Volume
| Issue : 1 | Page : 58-63
Imprint cytology: A boon in tissue diagnosis
Charusheela Rajesh Gore, Bikash K Singh, Shirish S Chandanwale, Sushma G Gurwale, Harsh Kumar, Rupali Bawikar, Indranil Dey
Department of Pathology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pune, Maharashtra, India
|Date of Web Publication||9-Jan-2017|
Dr. Charusheela Rajesh Gore
Department of Pathology, Dr. D. Y. Patil Medical College, Pune, Maharashtra
Source of Support: None, Conflict of Interest: None
Background: The technique of imprint cytology has provided great impetus to cytodiagnosis due to its simplicity, cost effectiveness, rapid results. It plays a significant role in the rapid diagnosis of the lesions. Objectives: To analyze the sensitivity and specificity of imprint cytology and thereby to evaluate its diagnostic utility. Materials and Methods: The prospective study was carried out in a tertiary care hospital. It included 105 cases. Both benign and malignant lesions from different organ systems were included in the study. Various techniques like touch imprints scrape cytology and squash preparations were used according to the nature of tissue sample. The cytodiagnosis was correlated with histopathological (HP) diagnosis to evaluate the sensitivity and specificity of imprint cytology. Results: Maximum lesions were of central nervous system (25.7%) followed by breast, head, and neck. Imprint cytology diagnosis had sensitivity of 95.5% with 100% specificity for detection of benign and malignant lesions. Overall accuracy of detecting type of lesion was 98.1%. Total discordance with HP diagnosis was found in 1.9% of cases. Conclusion: The use of smear technique in intraoperative diagnosis provides a rapid and efficient means of pathological assessment which in experienced hand, is capable of obtaining a high degree of accuracy. Its use is highly recommended routinely.
Keywords: Cytology, histopathology, imprint smears
|How to cite this article:|
Gore CR, Singh BK, Chandanwale SS, Gurwale SG, Kumar H, Bawikar R, Dey I. Imprint cytology: A boon in tissue diagnosis. Med J DY Patil Univ 2017;10:58-63
|How to cite this URL:|
Gore CR, Singh BK, Chandanwale SS, Gurwale SG, Kumar H, Bawikar R, Dey I. Imprint cytology: A boon in tissue diagnosis. Med J DY Patil Univ [serial online] 2017 [cited 2019 Jun 16];10:58-63. Available from: http://www.mjdrdypu.org/text.asp?2017/10/1/58/197924
| Introduction|| |
Imprint cytology is a major breakthrough in the field of rapid tissue diagnosis. Besides its speed and enormous simplicity, it provides excellent cellular details.
It is a special variation of applied cytology that can be used for various purposes and is a type of nonexfoliative cytology.,
Although histopathological (HP) appearance of a lesion in any organ is considered to be the final arbiter of its diagnosis, yet the delay involved may at times affect the course of treatment in certain situations. Imprint cytology intends to overcome this delay and save valuable time. This technique was utilized by Forkner  in 1927 for lesions of excised lymph node. Since then the development of newer staining techniques like papanicolaou (PAP) and Giemsa etc., have provided great impetus to cytodiagnosis.
Dudgeon and Patrick in 1927 and Bamforth and Osborn in 1958 have reported favorably about imprint technique. In 1999, the College of American Pathologists recommended that sentinel lymph nodes from breast cancer should be examined intraoperatively by cytologic methods for the staging of the disease.
Further, this technique not only conserves tissue but avoids freezing artifact, giving it an edge over frozen section analysis. Recently, use of imprint technique for rapid diagnosis in postmortem examination has been emphasized.
However, despite its enormous utility, imprint cytology has yet not received due attention and recognition. We attempted this study to assess the accuracy of interpretation of imprint smears. The study also analyses the sensitivity and specificity of imprint cytology technique, thereby carving a niche for imprint cytology in the diagnostic procedure.
| Materials and Methods|| |
A total of 105 cases tumors and tumor-like lesions were included in the study. Fresh specimens were collected from operation theater either on a wet gauze or in normal saline. Specimens sent in formalin were not included in the study. Gross pathological features were recorded before imprints were prepared. Specimens were trimmed in the following manner before taking imprints.
The lymph nodes and encapsulated tumors were bisected with a sharp knife in one plane.
The larger tumor masses were trimmed at half inch diameter, and imprint was taken from different areas.
Using filter paper excess blood or normal saline was soaked. Then a direct imprint was prepared by pressing a clean glass slide gently on the freshly cut surface of the specimen. In this manner, two to three imprints were obtained on one slide.
We also obtained material by scrape method. In this, fresh tissue was scraped from one end to the other by slide and minimum three smears were prepared. In certain cases like central nervous system (CNS) tumors, smears were obtained by crushing a small bit of tissue on a slide by the surface of another slide.
As soon as the imprints were obtained, the smears were immediately fixed in 95% ethyl alcohol for staining by rapid hematoxylin and eosin method and PAP stain. Few smears were air-dried for Leishman's stain. All the smears were observed under microscope.
The cytological diagnosis was correlated with histopathology, which was considered as gold standard. The sensitivity and specificity of imprint were calculated. Diagnostic accuracy of imprint cytology was established.
| Results|| |
A total of 105 patients were included in the study. There were female predominance 61 (58%) cases.
The majority of the patients (23.8%) were in the age group of 31–40 years. Only five cases were in the age group of ≤20 years. The benign lesions were predominant (58%) and were seen in the age group between 21 and 40 years as compared to malignant lesions which were common after 51 years of age [Figure 1].
There were 61 (58%) benign lesions and 44 (42%) malignant lesions [Figure 1]. Lesions from different organ systems were included. Maximum lesions were of CNS followed by breast, head, neck, gastrointestinal system (GIT), and lymphoreticular system (LRS) [Figure 2].
The degree of cellularity was analyzed among benign and malignant lesions. Most of the malignant lesions showed excellent cell yield [Figure 3].
Comparison between imprint and HP diagnosis was done [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]. Forty-two malignant lesions and 61 benign lesions were correctly diagnosed by imprint, thus showing sensitivity of 95.5% with 100% specificity. Positive predictive value of imprint was 100% whereas negative predictive value was 96.8% [Table 1].
|Table 1: Association between imprint and histopathological examination diagnosis|
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|Figure 4: (a) Imprint of medulloblastoma showing poorly differentiated cells with high N/C ratio and densely staining nuclei. (b) Histopathological examination of the same showing sheets of round to oval cells with hyperchromatic oval nuclei and little cytoplasm (H and E, ×400)|
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|Figure 5: (a) Imprint of melanoma showing discohesive sheets of large cells with pleomorphic nuclei and prominent large nucleoli. Focal intracytoplasmic brown pigment seen (Leishman, ×400). (B) Histopathological examination highlighting similar features (H and E, ×400)|
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|Figure 6: (a) Imprint of papillary carcinoma thyroid showing high cell yield with loose clusters of cells arranged in papillary pattern (Leishman, ×100). (b) Histopathological examination showed true complex papillae (H and E, ×100)|
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|Figure 7: (a) Imprint of renal cell carcinoma showing group of tumor cells with vesicular round to oval nuclei. The cytoplasm is moderate granular pink (H and E, ×400). (b) Histopathological examination of the same showing group of tumor cells with large nuclei and eosinophilic granular cytoplasm (H and E, ×100)|
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|Figure 8: (a) Imprint of gastrointestinal stromal tumor showing spindle to epithelioid cells with oval nuclei (H and E, ×400). (b) Histopathological examination of the same showing spindle-shaped cells arranged in fascicles (H and E, ×100)|
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|Figure 9: (a) Imprint of meningioma showing spindle cells with monomorphic nuclei and low N/C ratio (H and E, ×400). (b) Histopathological examination showing oval to spindle shaped cells arranged in whorls (H and E, ×100)|
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|Figure 10: (a) Imprint smear from low-grade glioma showing comparatively low cell yield with thin walled capillaries (arrow) (H and E, ×100). (b) High power of the same showing neoplastic nuclei (arrow), larger than normal glia (H and E, ×400)|
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|Figure 11: (a) Imprint smear from nodular sclerosis type H.D showing low cell yield with large anaplastic Reed–Sternberg cell (Leishman, ×400). (b) Histopathological examination of the same showing bizarre Reed–Sternberg cells. Also seen are areas of necrosis in lower part (H and E, ×400)|
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The diagnostic accuracy of the imprint was analyzed. All malignant cytological diagnoses turned out to be malignant on HP examination (HPE), however in three benign and malignant lesions each; we were unable to pinpoint the exact nature of tumor. There were two (1.9%) false negative cases on imprint. Thus, the overall accuracy in detecting the lesions by imprint was 98.1% [Table 2].
| Discussion|| |
The present study was conducted with an aim to evaluate the diagnostic utility of imprint cytology. A total of 105 cases were included in the study.
The benign lesions were seen in comparatively younger age group as compared to malignant lesions [Figure 1]. This was statistically significant for the occurrence of benign and malignant lesions. Similar finding was noted in the study conducted by Orki et al. who observed that mean age for malignant lesions was 54.2 years.
Among the study group, only six (6%) cases had poor cell yield, of which majority were benign lesion [Figure 3]. We analyzed the causes of poor cell yield. Among these six cases, two were of multinodular goiter in hyper involution, which on HPE showed thyroid follicles over distended with colloid and lined by flattened cells. In the third case of nodular sclerosis type Hodgkin's lymphoma, cell yield was comparatively low. This can be attributed to sclerosis. The fourth case of dermoid cyst of scalp showed mainly keratinous material, and hence cell yield was poor. In the fifth case, scrapings from endometrium were also not satisfactory. The sixth case of low-grade glioma also showed comparatively low cell yield.
All malignant cytological diagnoses turned out to be malignant on HPE [Figure 4], [Figure 5], [Figure 6], [Figure 7], however in three benign and malignant lesions each; we were unable to pinpoint the exact nature of tumor [Figure 8], [Figure 9], [Figure 10], [Figure 11].
There was total discordance between imprint and HPE diagnosis in two cases (1.9%) which were given as benign on the imprint, however, turned out to be malignant on HPE. Overall accuracy of detecting type of lesion was 98.1% [Table 1] and [Table 2].
The study conducted by Suen et al. showed that imprint technique had a wide application with overall accuracy of 96.3%. Lee  studied diagnostic value of imprint cytology in a retrospective study of 522 histologically proven tumors from various sites. The total diagnostic accuracy was 92.9%. Overall, the false-positive and false-negative rates were 0.8% and 4.8%, respectively. Similar findings were seen in a study conducted by Scopa et al. who evaluated tissue imprints in surgical pathology and found that intraoperative imprint cytology achieved an overall accuracy rate of 94.3%. For benign and malignant lesions, the accuracy was 97.5% and 91%, respectively. The diagnostic yield, when intraoperative imprint cytology and frozen section were used together was 99%.
Liang et al. analyzed the causes of discrepancy between results of touch imprint cytology and histopathology. The major cause they found was interpretation error followed by sampling error. The specificity, negative predictive value, and accuracy were 98.7%, 94.6%, and 93.8% respectively in their study.
Association between imprint diagnosis and HPE diagnosis of breast, female genital tract and hepatobiliary lesions in study group showed that all malignant and benign lesions were correctly diagnosed by both the techniques. Thus accuracy was 100%. This was comparable with few other studies.,,,,,,,,
For GIT lesions, the overall accuracy of detecting lesion was 90.9%. We have come across some earlier studies where the overall diagnostic accuracy was 98%–100%.,,
All the benign cases were correctly diagnosed by imprint, while in one malignant case, differential diagnosis was offered. It was a small intestine tumor which on imprint cytology showed cellular fascicles of spindle cell with moderate pleomorphism. The diagnosis offered was of malignant spindle cell lesion with differentials of leiomyosarcoma and gastrointestinal stromal tumor (GIST). Later, it turned out to be malignant GIST on HPE [Figure 8]a and [Figure 8]b.
The association between imprint diagnosis and HPE diagnosis in CNS lesions showed that the overall accuracy in detecting lesions was 92.6%. Comparable results were found in study by Savargaonkar and Farmer  and Firlik et al.
In CNS, all the malignant cases were diagnosed correctly by imprint; however, in benign lesions, we were unable to pinpoint the diagnosis in two cases. In the first case, the tumor showed streaming fascicles of spindle-shaped cells without much pleomorphism or mitoses. We were unable to differentiate between meningioma and schwannoma on imprint alone. It turned out to be a schwannoma on HPE [Figure 9]a and [Figure 9]b.
In the second case, the smears were showing low cell yield. It was difficult for us to differentiate slightly larger nuclei of tumor from normal glial cells. Hence, the confident diagnosis of low-grade glioma could not be offered [Figure 10]a and [Figure 10]b.
The head and neck lesions showed that the overall accuracy in detecting lesion is 93.3%. Various other studies have shown it in the range of 89%–97%.,,,,
All the malignant cases were diagnosed correctly by imprint while there was difficulty in differentiating follicular adenoma from adenomatoid nodule in multinodular goiter. On HPE it turned out to be adenomatoid nodule. This is a very common difficulty faced by the pathologists.
The association between imprint and HPE diagnosis of kidney urinary bladder lesions showed that the overall accuracy of imprint in detecting lesions was 85.7%. All the benign cases were correctly diagnosed. Among one of the malignant cases where cytology showed pleomorphic spindle cells, the exact nature of these cells was difficult to guess on cytology alone. The HPE diagnosis, in this case, was malignant peripheral nerve sheath tumor.
Among the 11 cases of LRS, there was diagnostic difficulty faced in two. One of the cases on imprint showed poor cell yield, with few anaplastic tumor cells. Considering this, diagnosis of metastatic carcinoma was entertained. However, this turned out to be nodular sclerosis type of Hodgkin's lymphoma [Figure 11]a and [Figure 11]b. In the second case, imprint smears showed necrotic material admixed with acute inflammatory cells and few ill-formed granulomas. Considering this, the diagnosis of granulomatous inflammatory pathology was considered. However, HPE sections showed abscess with few malignant squamous cell. These were obscured on imprint smears due to the presence of necrotic material. The overall accuracy in detecting lesions in LRS in our study is 81.8% with sensitivity of 89%. There are some studies done on lymph node imprint cytology which showed sensitivity of 64%–93% and accuracy of 86%–98%.,,
Association between imprint and HPE diagnosis of skin and soft tissue lesions showed an overall accuracy of 75%. The low accuracy rate can be attributed to small sample size in this group. All the benign cases were correctly diagnosed on imprint; however, there was discordance in one of the cases where the imprint diagnosis was suggestive of lipoma however it turned out to be well-differentiated liposarcoma on HPE. The lipoblasts were not appreciated on imprint preparation. This is one of the disadvantages in these lesions. The earlier studies with larger sample size have shown better correlation.,
| Conclusion|| |
The imprint smear technique is simple and rapid and does not require any sophisticated instruments. There are certain advantages like the cellular details are better appreciated, and it can be used routinely as an adjunct to frozen section in rapid intraoperative evaluation. The limitations which we faced were in lesions with spindle cell morphology. These were difficult to interpret correctly on imprints alone. One can give close differentials for such lesions. Another problem faced was with necrotic tissue, where the necrotic material obscures the cellular details. Care should be taken in reporting such slides. We also recommend study of the individual system, with larger sample size for better data collection.
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Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8], [Figure 9], [Figure 10], [Figure 11]
[Table 1], [Table 2]