Pathology — Specimens, Reports and Test Interpretation, NMC MBBS licence examination syllabus (Nepal Medical Council).
A pathology report describes the tissue in the pot. Whether that tissue came from the lesion you were worried about is your problem, not the pathologist's.
The first two pathology chapters covered what disease does to tissue. This one covers the part a candidate uses every working day afterwards: choosing a specimen, reading what comes back, and knowing what a result can and cannot settle.
Three ways of sampling a lesion, and each can answer a different question. Choosing the wrong one wastes the procedure.
Cytology collects loose cells — from a needle passed into a lump, from a smear, from a fluid. It is quick, cheap and low-risk, and it can say that the cells look malignant. What it cannot show is invasion, because invasion is not a property of a cell: it is a relationship between cells and the tissue around them, and that relationship is destroyed when the cells are separated.
Needle biopsy takes a core with the architecture intact. It can show invasion, and it can usually type the tumour, which is what treatment depends on.
Excision removes the whole lesion with a rim of surrounding tissue. It is the only specimen that can report whether the margins are clear — whether the disease has been fully removed.
The practical test is a single question: does the report explain the clinical finding? If a hard, fixed, growing mass returns "normal fibrofatty tissue", those two facts do not fit together. The sample is far likelier to be the problem than the examination.
The wrong container. Fixative preserves tissue architecture for histology and kills organisms in the process. A specimen sent for culture in fixative arrives sterile and useless. If both are needed, both containers are needed — and the decision has to be made in the room, not afterwards.
No clinical detail on the form. A pathologist given "lump" reports differently from one told the patient's age, the site, how long it has been there and what you are worried about. The report is an opinion formed on the information available, and starving it of context makes it less useful.
The unlabelled or mislabelled pot. This is the error that can give one patient another patient's diagnosis, with an operation or a course of treatment following from it. Labelling at the bedside, against the patient, is the habit that prevents it — not labelling later from memory at the desk.
A test does not answer whether the patient has the disease. It changes how likely the disease already was. That sounds abstract until it is put concretely: the same result means different things in two different patients.
Where a disease is unlikely to begin with, most positive results will be false ones, and each false positive starts an investigation with its own risks and its own anxiety. Where a disease is very likely, a negative result may not be enough to abandon the diagnosis. NMCCM03 covers this from the screening side; the point here is at the bedside.
The habit worth building: before ordering a test, ask what you will do with each possible answer. If a positive and a negative lead to the same action, the test does not change management — and ordering it anyway generates findings that have to be explained.A woman has a breast lump; cytology reports malignant cells. This is enough to know the cells are malignant and to proceed with staging discussions, but not enough to plan surgery — a core biopsy is needed to type the tumour and confirm invasion.
A neck lump is biopsied; the report says "normal lymphoid tissue". If the lump is persistent, hard or growing, the report and the patient do not agree. Discuss with the pathologist and consider repeating rather than reassuring.
A specimen from a chronically discharging wound is sent in fixative. Histology may be informative but culture is now impossible, and in a discharging wound the organism is usually the question. Both containers were needed.
A screening test is positive in a young patient with no risk factors and no symptoms. Before acting on it, consider how likely the disease was beforehand. In a low-risk group most positives are false, and repeating or confirming is often more appropriate than starting treatment.
Cytology and biopsy. Cytology looks at cells; biopsy looks at cells within tissue. Only the second can demonstrate invasion, which is why the two are not interchangeable.
"Negative" and "excluded". A negative report excludes disease in the sample examined. Whether it excludes disease in the patient depends entirely on whether the sample was representative.
Clear margins and cure. Clear margins mean the excised specimen had tumour-free edges. It is good news and it is not a guarantee, because disease may already have spread beyond the specimen.
Cytology — cells, no architecture, cannot show invasion. Core biopsy — architecture, can show invasion and type. Excision — the only one that reports margins.
"No malignancy seen" describes the sample, not the patient. Ask whether the report explains the clinical finding.
A report that contradicts a strong clinical picture is discussed and repeated, not filed.
Fixative kills organisms — histology and microbiology need separate containers.
Label at the bedside. The mislabelled pot is the error that gives a patient someone else's diagnosis.
Before ordering, ask what each possible result would change. If nothing, the test is not needed.
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