Histopathology is the science of looking at tissues related to diseases. Meanwhile, cytology is the science of looking into individual cells. Thus, this is the key difference between histopathology and cytology.
Moreover, histopathological examinations are more invasive and traumatic, while cytological examinations are less invasive and traumatic. Histopathology is the study of the signs of diseases using the microscopic examination of tissues.
On the other hand, cytology is the study of cells in terms of structure, function and chemistry. Both histopathology and cytology are widely used in medicine in order to diagnose and prevent diseases. In both studies, it is necessary to make glass slides of specimens, stain them using suitable dyes and examine under a microscope.
It is also necessary to observe slides by a specialized trained person often by a doctor. Thus, this is the summary of the difference between histopathology and cytology. Samanthi Udayangani holds a B.
Degree in Plant Science, M. This is an excellent comparison. Thank you for writing it. I write research papers for my Facebook group, The Science of Avian Health, and I would like to use some of the information in this article. Please grant me permission to do so. Cytopathology is a boarded subspecialty of Anatomic Pathology. Broadly defined it is a diagnostic discipline that requires application of distinct and discrete sets of criteria for evaluation of patient samples from diverse anatomic locations.
Specific diagnostic criteria are required because the unifying theme of cytology samples is the fact that cells are dispersed and therefore present outside the context of tissue architecture. That is to say, cells are either smeared onto a slide conventional Pap test; brushings from airway, bile duct, etc. Although the primary function of a cytopathologist is to appropriately apply cytopathologic criteria to arrive at an accurate diagnosis, it is also necessary to understand specimen procurement and specimen processing.
It is essential for the cytopathologist to appreciate when a diagnosis cannot and should not be proferred; to appreciate the importance of clinical history in the formulation of Differential Diagnoses; and to appreciate the impact of a cytologic diagnosis on patient management.
The cytopathologist is a patient advocate that may decide when a procedure may be performed and which ancillary tests may be indicated. A cytopathologist performs FNA biopsies or assesses adequacy of an FNA procedure performed by another practitioner and as such is directly involved in patient care. Even when the cytopathologist is not involved in the performance of procedures, appropriate interaction with clinicians is critical in ensuring that patients receive optimal care.
These are all activities in which many competencies play a role and become particularly interwoven. The cytopathologist must be able to appropriately triage specimens to permit optimal diagnostic evaluation and to avoid the need for repeat procedures.
Faculty, staff and residents are always involved in projects and opportunities for presentation and publication that enhance the cytology service. Inflammatory changes: As described before, sometime extensive inflammation may obscure cellular details and prevent appropriate interpretation. To avoid this problem, treating the patient and repeating the procedure afterwards is recommended.
Certain changes are induced by these treatment modalities. To decrease the pitfalls from these changes, appropriate and detailed history should be given by clinicians and awareness of the changes by the pathologist should be taken into consideration. Atypical cellular changes related to hemorrhage, infarction, or necrosis can be problematic. Awareness of these changes by the cytopathologist is very helpful to prevent both false positive and false negative diagnosis.
Despite efforts to be as accurate as possible, both false negative[ 95 — 99 ] and positive[ — ] diagnosis can still occur. False negative diagnoses are most commonly related to:. Desmoplasia: This is defined as the presence of fibrosis which is induced by certain tumors due to secretion of fibrogenic materials.
Many tumors can cause fibrosis around the malignant cells. The most notorious are mammary, pancreatic and billiary tree carcinomas in addition to nodular sclerosing Hodgkin's lymphoma. Applying negative pressure and multiple passes during the FNA procedure can help. Well-differentiated tumor cells: Certain tumors are extremely well-differentiated and they resemble their original cells.
For example, well differentiated thyroid follicular carcinoma and well differentiated hepatocellular carcinoma can be deceiving. Awareness of these tumors and appropriate understanding of limitations of cytology is recommended. In these circumstances, making the final diagnosis on tissue sections probably is more appropriate. Sampling problems: Sometimes the needle is not in the appropriate lesion of interest.
This can be resolved by having an experienced aspirator and judicious utilizing of image guidance. The presence of inflammation, radiation, and chemotherapy changes sometime can be over interpreted. Applying strict cytological criteria in these situations is very helpful. Pregnancy: Pregnancy sometimes can increase cell size in Papanicolaou smears. Awareness by the pathologist and providing appropriate history is recommended.
Contamination: Contamination can occur either through the needle tract or during processing. Awareness of this potential problem and being diligent regarding following the safety protocols between cases is very important and will decrease the impact of this issue. Inflammation and inflammatory changes, radiation and chemotherapy effects sometimes will lead to false positive diagnosis.
Awareness and applying strict criteria after receiving accurate history is the key to avoid this diagnostic trap. The presence of hemorrhage and infarction sometimes induce atypical changes in the cells. Awareness of this issue, which includes the presence of necrotic material and blood elements, should alert the pathologist to avoid false positive diagnosis.
Inexperience by the pathologist may induce false positive diagnosis. To eliminate this issue, consultation with other colleagues in the department of pathology is always helpful.
As part of routine quality control and quality assurance in the cytopathology laboratories, it is highly recommended to have two pathologists co-sign any new diagnosis of malignancy. Each organ has its own diagnostic limitation by cytology. However, common examples are provided in this list:. A reactive mesothelial cell versus well differentiated mesothelioma is sometimes difficult. Correlation with the clinical and radiological picture is always helpful. Glandular lesions on Pap smears.
Those are sometimes difficult, and communication with a gynecologist in the same situation to establish a common language and triaging protocols are very helpful. Breast: Ductal carcinoma in situ versus invasive ductal carcinoma is difficult to do on cytology. In addition, lobular lesions are sometime easily missed on cytology material.
Awareness of these lesions and common language communication with the clinician is very helpful. Respiratory lesions: Small cell carcinomas cells in sputum cytology sometimes are missed due to their small size and marked degeneration.
Well-differentiated carcinomas in general are not easy to diagnosis. Awareness and correlation of the clinical, radiological, and bronchoscope picture is very helpful.
Urinary cytology: Low grade transitional cell lesions are difficult to diagnose by urine cytology. Communication with the urologist and correlation with the cystoscopic picture is of optimum importance. Lymph nodes: The diagnosis of low-grade lymphoproliferative disorders is difficult based on cytology alone. To eliminate this issue, using the ancillary studies with immunophenotypic analysis either by immunohistochemistry or flow cytometry is very critical. Soft tissue: Low grade neoplasms are sometime difficult.
Awareness of the clinical and radiological picture with appropriate sampling and excellent communication with the clinicians is very helpful. Prostate: There is a consensus agreement that FNA of the prostate is not recommended since differentiation between prostatic intraepithelial neoplasia and invasive carcinoma is practically impossible based on cytomorphology alone. Pancreas: FNA of pancreatic lesions, especially if there is pancreatitis, may give rise to false positive diagnosis.
Awareness of the patient's history and the presence of calcification on radiological images are very helpful clues. In addition, cystic neoplasms are difficult to further be specified based on cytological examination alone. Central nervous system: As it is difficult on surgical biopsies, separating low grade gliomas from gliosis is also difficult on cytomorphology.
When screening CSF samples or contents aspirated from brain reservoirs, awareness about tumors that shed cells is very helpful. Utilizing the science of cytopathology whether exfoliative or FNA is cost effective, fast, simple and accurate. Team work emphasizing excellent communication skills is very important between pathologists and clinicians. All the information about the patient should be given to the pathologist in order to decrease the frequency of pitfalls that were described.
Encouragement of clinical pathologic correlation conferences and tumor boards is very helpful to establish common language and protocols with appropriate guidelines for diagnostic utilization of cytology materials. Source of Support: Nil. Conflict of Interest: None declared.
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Abstract This overview is intended to give a general outline about the basics of Cytopathology. Keywords: Cytology, fine needle aspiration. Open in a separate window. Figure 1. Figure 4. Figure 2. The optimum goal is to reach a definitive diagnosis This objective is the ultimate goal. As a screening tool The success story of utilizing Papanicolaou smears in detecting early precursor lesions of cervical cancer is well known in the developed word.
As a follow-up for different diseases Cytological examinations of specimens taken from different sites as a follow-up after establishing the initial diagnosis is a routine procedure. For determination of different prognostic factors in neoplasia diagnosis This is usually achieved as part of staging or using the cytological samples to perform ancillary studies, such as Her-2Neu analysis on breast mass aspirates.
Simple It is well known that getting most cytological samples is simple. Quick The procedure is very quick and diagnostic answers can be provided immediately at the time of procedure, if needed, or within the next hours. Cost effective The cost effectiveness of cytological examination is well documented in the literature, a feature that is becoming very critical given the current high health care costs. This includes: Gynecological samples: Papanicolaou smears are the first samples that started the exponential revolution of the cytopathology field.
Aspiration cytology Different names are used to describe this expanding technique. This technique has been used from any lesion in the body which includes two major areas: Palpable lesions: Palpable lesions can be targeted by a clinician and preferably by an experienced cytopathologist. Different types of smear preparations are utilized in the cytopathology laboratory, which includes: Direct smears as described above.
Figure 5. Figure 6. These include: Simple special stains such as stains for microorganisms. Figure 3. Adequacy It is recommended that a statement describing if the material was adequate to make an interpretation is inserted in the final report.
Diagnosis A specific diagnosis is always desired when possible. Descriptive diagnosis microscopic description Sometimes descriptive diagnosis and microscopic description of the smears may be helpful for the clinicians to make a therapeutic decision. Comment In certain circumstances a comment is needed to clarify or add some information that may harbor clinical importance. Recommendations Sometimes we need to call the clinicians and discuss the case with him either face to face or over the telephone.
Sometimes the material is sub optimal due to multiple factors, the most frequent are: Air drying artifacts leaving the smears for too long before staining. False negative diagnoses are most commonly related to: Desmoplasia: This is defined as the presence of fibrosis which is induced by certain tumors due to secretion of fibrogenic materials. On the other hand, false positive diagnosis is usually caused by: Pregnancy: Pregnancy sometimes can increase cell size in Papanicolaou smears.
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