Clinical laboratory

Skin biopsy is an essential procedure in skin disease management, used for diagnosis as well as therapeutic purposes, performed with utmost professionalism by our doctors at TOP-DERM CLINICS.

Diagnosis accuracy depends on correct biopsy procedure, choosing the optimal site/lesion, adequate tissue sampling, proper biopsy specimen handling, using adequate transport media and providing the dermatologist with detailed clinical data.

The most frequently used biopsy procedures are: punch, shave, incisional, excisional, each with its own advantages and information provided.

Punch biopsy is the most utilized procedure both for diagnosis and therapeutic purposes. It is the method of choice for inflammatory dermatoses diagnosis, facilitating full-thickness skin assessment, from the epidermis to the superficial layer of hypodermis. Specific instruments are used, with preset sizes, the 4 mm diameter providing an adequate tissue sample for histopathological examination. It can also be used to remove small-size-growths (nevus, warts, keratosis, etc.) Punch biopsy is to be avoided in pigmented lesions, partial biopsy specimen being used to avoid atypical or malignant areas.

Shave biopsy involves sampling the outer layer skin lesion with a scalpel blade, being preferred for lesions limited to the epidermis. Ideal biopsy depth depends on the doctor’s experience, to ensure a balance between diagnosis accuracy and aesthetics. Superficial lesions such as seborrheic keratosis can undergo such biopsy. It is however a method to be avoided in cases with uncertain diagnosis or suspicion of malignant lesion due to absence of deeper tissues for histopathological evaluation.

Excisional biopsy consists of complete sampling of the entire skin lesion, including in-depth layer up to the subcutaneous tissue. This method is preferred when suspicions of malignant tumor arise. It requires more time and experience compared to other biopsy methods, but it supplies the anatomopathologist with more tissue and data. It consists of an elliptical excision of the skin lesion and suture.

Incisional biopsy is recommended in deep inflammatory processes (such as panniculitis, porokeratosis, ulcers, medium vessel vasculitis), when the shave biopsy would result in unaesthetic appearance or when the punch biopsy wouldn’t provide a representative tissue sample. The procedure is similar to excisional biopsy, except that it only samples part of the lesion, and the sample must include an area of 1 mm of perilesional tissue.

Immunohistochemistry (IHC) is a biological procedure with countless medical applications that was first conceptualized by Coons et al., primarily used in cancer diagnosis. Dermatopathology plays an essential role in the diagnosis of skin conditions, however, in some cases, these take on similar histopathological characteristics, in which situation immunohistochemistry has become an indispensable tool not only for differential diagnosis but also for treatment planning and prognosis of cutaneous neoplasms.

Developed from the antigen–antibody binding reaction, IHC is the main method of establishing the origin of  a tissue or of differentiating neoplastic cells.

In recent years, aside from the proteins frequently utilized, numerous markers with high sensitivity and specificity have been tested in this field.

Immunohistochemistry is frequently used for neoplastic diseases such as melanocytic tumors, hematolymphoid neoplasms, with fusiform cells and cutaneous metastases, cutaneous metastasis, although it can have a wide range of applications

Frequently used markers in melanoma diagnosis:

• S100 protein:  it is a high sensitivity marker for cutaneous melanoma, being positive >95% of cases, but with low specificity
• Gp100 (HMB 45): a relatively specific marker, yet also detected in benign melanocytic nevus
• MART1/MelanA: considered an important marker for melanoma diagnosis; it can be present in some benign melanocytic lesions as well
• Ki67: it is an active cell proliferation marker, > 10% positivity suggests melanoma diagnosis; it is correlated with the vertical growth phase, thus being a prognostic indicator
• SOX10: sensitive and specific marker for melanoma and for ganglia metastasis detection