Clinicopathological correlation

Clinicopathological correlation is the comparison of clinical observations with the findings in a pathological specimen to determine whether they form a coherent account of the same process. In dermatopathology, the clinical observations can include lesion location, appearance, size and change over time, while the specimen supplies microscopic tissue organization. These are complementary observations, not interchangeable measurements.

A skin biopsy is removed tissue sent for microscopic assessment and a written pathology report, as described by the American Academy of Dermatology.^[ref] Relating the report to the clinical question requires knowing what was sampled. A sample from the edge, the centre or an unrelated nearby site need not contain the same structures.

An original geometric example illustrates the issue. Suppose an observed lesion has a circular surface footprint $8\mathrm{mm}$ across and a circular $2\mathrm{mm}$-diameter sample lies wholly inside it. The sample covers the fractionof that projected area. This does not say that the remaining area has the same histology, or that one sixteenth of the three-dimensional lesion volume has been examined. It shows why a local finding cannot automatically stand for the complete visible lesion.

Correlation can also expose a mismatch: the tissue pattern may not account for the reported location or extent, or the specimen description may not match the documented sample. That discrepancy is information to investigate rather than a reason to force agreement. Conversely, a compatible clinical history does not prove every microscopic interpretation. Keeping the original observations and the resulting inference separate makes the reasoning testable.

In a study of the added value of clinical information, the same specimens could be interpreted with prespecified information withheld and then supplied, while controlling reading order and access to previous answers. The outcome would be a change in defined interpretations or reference agreement. Improvement cannot be assumed merely because more contextual information is available.