Information on the skin biopsy
The timing of the biopsy
Avoiding secondarily-changed lesions
Since the progress of a disease needs to be recorded as representatively as possible in a biopsy, the efflorescences should not be affected by any external influences. Scratching or rubbing at a lesion can impair the ability to make an assessment. Thus, in psoriasis cases we generally see a parakeratosis at a narrowed Stratum granulosum; however, with long-term rubbing a compact orthokeratosis and expansion of the Stratum granulosum can also occur. Excoriated lesions frequently show neutrophile granulocytes, focal fibrin precipitates and plasma deposition at the horny cell layer, through which the underlying course of the disease can be obscured. An irritation or super-infection of skin tumours often accompanies atypical nuclei and mitoses, which can lead to faulty carcinoma diagnosis in malignant neoplasias (e.g. seborrhoeic ceratosis) or hyperplasias (e.g. Verruca vulgaris). In such cases, the biopsy should be postponed and an anti-inflammatory or antibacterial local treatment should be performed first of all. Conversely, advance treatment can also complicate diagnosis: thus, there is often no evidence of the presence of fungi in the horny cell layer following local anti-mycotic therapy, and pre-treatment with corticosteroids can alter the density and composition of an inflammatory filtrate. In general, great care should be taken with inflammatory dermatoses that the efflorescences to be biopsied are fully developed and have not been altered secondarily. The significance of the histopathological examination will then be greatest.