Skin Biopsy in Dermatology: Classification, Technique, and Diagnostic Value
Skin biopsy. This article covers punch, shave, and excisional techniques, specimen handling and fixation, and the role of biopsy in dermatology and oncology.
Diascopy in Dermatology: Mechanism of Action, Technique, and Differential Diagnosis of Skin Lesions
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Diascopy is a simple yet informative diagnostic method in dermatology, based on the examination of skin changes under pressure. This technique is still used in modern dermatology due to its high diagnostic effectiveness and accessibility. Diascopy was first described in the late 19th century and remains in clinical use today.
Principle and Mechanism of Diascopy
Diascopy is performed by applying light pressure to the skin surface with a transparent glass or plastic spatula. For this purpose, a diascopic device with illumination or a dermatoscope may also be utilized. The procedure is based on the phenomenon of optical clearing of the epidermis under compression, which allows the healthcare professional to visually determine the nature of morphological elements, specifically:
- To differentiate hemorrhagic (bleeding) from erythematous (inflammatory) lesions.
- To detect hidden pigmentation.
- To assess vascular structures.
Step-by-Step Technique of Skin Diascopy
Diascopy is performed in several steps:
- Preparation: the skin area to be examined is cleaned.
- Application: the diascopic instrument is pressed firmly against the area until the surrounding tissues blanch.
- Evaluation: changes in skin elements under pressure are assessed.
- Revascularization: the time required for color restoration after pressure is recorded.
- Interpretation: the results are analyzed.
Evaluation of Results: Positive and Negative Diascopy
The changes observed under pressure are differentiated into:
- Positive diascopy: the lesion disappears or changes its color (typical for vascular and inflammatory lesions).
- Negative Diascopy: no change in color is observed (typical for hemorrhagic and certain pigmented lesions).
Differential Diagnosis in Dermatology
Vascular Lesions
- Eczema, dermatitis: due to their inflammatory nature, the lesions tend to blanch under pressure and immediately regain color.
- Vasculitis: lesions do not disappear, as they are caused by hemorrhage.
- Telangiectasias: these lesions may blanch slightly but retain their distinct vascular pattern.
- Hemangiomas: upon examination, these elements blanch, then slowly regain color.
Pigmented Skin Lesions
- Dermal nevi: color remains unchanged.
- Melanoma: uneven pigmentation and abnormal color persist.
- Dermatofibroma: the pigment may blanch slightly; the “dimple sign” is observed.
- Hemosiderosis: lesion color intensity diminishes.
Infectious and Inflammatory Diseases
- Lupus vulgaris, sarcoidosis: the “apple jelly” sign is observed, with yellow-brown nodules visible.
- Granuloma annulare: firm papules blanch slightly.
- Roseola (in syphilis, toxicoderma, rubella, measles, typhus or typhoid fever): lesions disappear under pressure.
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Advantages and Limitations of Diascopy
Advantages
- The technique requires minimal time.
- It is completely safe and painless.
- No specific patient preparation is needed.
- The method does not require complex or expensive instruments.
Limitations
- Diascopy does not replace histological examination.
- The method has low informative value for deep-seated lesions.
- It requires extensive expertise for correct interpretation.
FAQ
1. What are the main indications for diascopy?
Diascopy is indicated for differential diagnosis of vascular (vasculitis, hemangiomas), pigmented (nevi, melanoma), and infectious/inflammatory skin lesions.
2. Can diascopy be used instead of skin biopsy?
No. Diascopy is an auxiliary method that aids in preliminary diagnosis and differentiation. It does not replace skin biopsy (histological examination), which remains the gold standard for definitive verification of many pathologies.
3. When is diascopy least informative?
Diascopy is less informative for deep-seated lesions, since surface pressure cannot adequately empty vessels or lighten pigment in deeper dermal or subcutaneous layers.
4. What is positive diascopy?
Positive diascopy means that the lesion disappears or changes color under pressure. This sign is typical for lesions caused by inflammation or vascular dilation (erythema, telangiectasias).
5. When does the “apple jelly” sign apply?
The “apple jelly” sign, revealed by diascopy, is characteristic of lupus vulgaris and sarcoidosis, where yellow-brown nodules resembling jelly are visualized.
References
1.
VOKA Catalogue. [Electronic resource].
https://catalog.voka.io/
2.
Dermoscopy in general dermatology: practical tips for the clinician British Journal of Dermatology, Volume 170, Issue 3, 1 March 2014, Pages 514–526.
3.
Matos D, Coelho R. “Apple Jelly” Sign: Diascopy in Cutaneous Sarcoidosis. Acta Med Port. 2015 May-Jun;28(3):394. doi: 10.20344/amp.5396. Epub 2015 Jun 30. PMID: 26421796.
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Скрипкин, Ю. К. Дерматовенерология. Национальное руководство / под ред. Ю. К. Скрипкина, Ю. С. Бутова, О. Л. Иванова. – Москва : ГЭОТАР-Медиа, 2014. [Skripkin, Yu. K. (2014). Dermatovenerologia. National’noye rukovodstvo (Dermatovenereology: National guidelines) Skripkin, Yu.K. (Ed.), Butov, Yu. S. (Ed.), Ivanova, O. L. (Ed.). Moscow: GEOTAR-Media]. – 1024 с.
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Clinical Dermatology: A Color Guide to Diagnosis and Therapy 6th Edition by Thomas P. Habif MD (Author).
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Dermatology, 5th Edition. Author : By Jean L. Bolognia, MD, Julie V. Schaffer, MD and Lorenzo Cerroni, MD.
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