Immunohistochemistry for dermatofibroma

No single stain should be read alone. The pathologist combines the stain pattern with cell shape, growth pattern, lesion depth, borders and the clinical information supplied with the biopsy.

A dermatofibroma is a usually benign fibrous skin growth. Its cells commonly show factor XIIIa staining and are often negative or only focally reactive for CD34, whereas some look-alike spindle-cell tumours may show a different distribution. Results can overlap, so these markers are clues rather than stand-alone verdicts.

Additional stains may be selected when the sample has unusual features or when the pathologist is considering another fibrous, nerve-related, muscle-related or melanocytic lesion. The panel is tailored to the microscopic differential diagnosis.

Review whether the report gives a clear diagnosis, describes any atypical features and comments on the specimen edges. A small biopsy may establish the type of lesion without removing it completely, so an involved edge does not by itself mean the growth is malignant.

If the findings are uncertain, the care team may request deeper tissue sections, more stains, review by a dermatopathologist or a larger sample. Management depends on symptoms, diagnostic confidence, growth behaviour and whether the lesion remains after sampling.

Arrange reassessment if the lesion grows quickly, changes notably, repeatedly bleeds without being knocked, becomes persistently painful or returns after removal. These changes do not determine the diagnosis, but they give the clinician a reason to examine or sample the area again.

After a biopsy, seek prompt advice for spreading redness, increasing warmth or swelling, pus, fever, uncontrolled bleeding or worsening pain at the wound.

Ask whether the microscopic appearance and stains agree, which alternative diagnoses were considered, whether the sample was adequate and whether any atypical features were present. Clarify whether observation, complete removal or specialist pathology review is recommended.