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.
Primary Morphological Elements of Skin without Cavity: Classification, Clinical Manifestations
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Primary morphological elements are changes in the skin and mucous membranes, induced by various pathological processes.
Five primary sexless morphological elements are distinguished:
- Macule (macula);
- Papule (papula);
- Tubercle (tuberculum);
- Nodule (nodus);
- Blister (urtica).
3D Models of Primary Morphological Elements without Cavity:
Vascular Inflammatory Macule
Vascular Non-Inflammatory Macule
Vascular Hemorrhagic Macule
Hyperpigmented Macule
Hypopigmented MaculeMacule (Patch)
A macule is a primary morphological element without cavity that appears on the skin or mucous membranes characterized by color change within a limited area. Macules are always flat and do not leave scars on the skin after resolution.
International sources classify macules by size as follows:
- A macule is a spot less than 1 cm in diameter;
- A patch covers more than 1 cm in diameter.
Depending on the nature, macules may be:
- Non-inflammatory;
- Inflammatory.
By origin, macules are categorized into:
- Vascular;
- Hemorrhagic;
- Pigmented.
Vascular Inflammatory Macule
Vascular inflammatory macules appear as a result of dermal vascular dilation against the backdrop of an inflammatory reaction, which disappear when pressure is applied (diascopy).
Macules may be pale pink to bright red, typically irregular in shape and margins undefined.
Macules up to 1 cm in diameter are called rozeolas, whereas spots over 1 cm are called erythemas.
These macules can occur in diseases such as syphilitic and infectious roseola, eczema, dermatitis, rosacea, and lupus erythematosus.
Vascular Non-inflammatory Macule
Vascular non-inflammatory macules result from temporary or permanent enlargement of skin vessels without an inflammatory response that do not disappear when pressure is applied (diascopy).
Examples include emotional erythema or flushing, hemangiomas, or telangiectasias.
Vascular Hemorrhagic Macule
Vascular hemorrhagic macules are non-inflammatory macules that occur when blood elements are released from the vascular bed into the surrounding tissues due to mechanical rupture of the vessel wall (trauma, bites) or an increase in its permeability (vasculitis, blood diseases).
By size, these macules are classified into:
- petechiae — up to 2 mm;
- purpura — 2 mm up to 1 cm;
- ecchymosis — over 1 cm.
Massive outpourings of blood into tissues are called hematomas.
When pressed upon, such macules do not disappear. During recovery, they may change color from bright red to yellow and green.
Hyperpigmented Macule
Non-inflammatory macules associated with excessive deposition of melanin are called hyperpigmented macules.
By origin, they are classified into:
- Сongenital (nevi);
- Acquired (chloasma, freckles, lentigo);
- Drug-induced (toxic melanoderma);
- Artificial (tatoos, permanent makeup).
Hypopigmented Macule
Non-inflammatory macules associated with partial or complete absence of melanin deposition are called hypopigmented macules.
Skin hypopigmentation may be:
- total congenital (albinism);
- local acquired (vitiligo).
Papule (Plaque)
A papule is a primary morphological element of a skin rash without a cavity that has a dense-elastic consistency and protrudes above the skin surface. After resolution, they do not cause scarring, but may leave temporary or permanent pigmented spots.
3D Models of Primary Morphological Elements Without Cavity:
Epidermal Papule
Dermal-Epidermal Papule
Dermal PapuleClassification of Nodules / Plaques
By depth:
- Epidermal — callus, wart, molluscum contagiosum, palmoplantar keratodermas;
- Dermal-epidermal — psoriasis, lichen planus, neurodermatitis, eczema, lupus erythematosus, dermatitis herpetiformis or Duhring disease, leprosy.
- Dermal — for example, papular syphilid (secondary syphilis).
By size:
- Papule (papula) — up to 1 cm in diameter;
- Plaque (plaque) — more than 1 cm in diameter.
By origin:
- Inflammatory:
- Proliferative processes in the epidermis: acanthosis (thickening of the spinous layer, for example in eczema); hypergranulosis (thickening of the granular layer, for example in lichen planus); hyperkeratosis (thickening of the stratum corneum, for example in palmoplantar keratodermas).
- Infiltrative processes in the dermis (for example, in secondary syphilis).
- Non-inflammatory:
- Metabolic — deposition of metabolic products (amyloid, lipids, mucin, etc.);
- Neoplastic.
By shape:
- Flat (epidermal, dermal-epidermal);
- Hemisphere‑shaped (dermal);
- Pointed (follicular).
By color:
- Skin‑colored (sebaceous gland adenoma, molluscum contagiosum);
- Violaceous (lichen planus);
- Reddish (psoriasis, exanthema, secondary syphilis, acute prurigo);
- Brown (pigmented urticaria, histiocytosis);
- Bluish (blue nevi, Fabry disease);
- Yellow (xanthomas, histiocytosis, granulomatous dermatosis);
- Black (certain types of nevi, Kaposi sarcoma).
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Nodule
A nodule is a primary morphological element of a skin rash without a cavity, usually round, with a diameter starting from 1 cm. It is characterized by varying depth (most often in the deeper layers). On palpation, a nodule feels firmer than a papule. It may ulcerate, leaving a scar.
A nodule most commonly occurs in lipoma, and may also be seen in tertiary syphilis, tuberculosis, leprosy, cutaneous leishmaniasis, erythema nodosum, intradermal nevi, and cysts.
Classification of Nodules by Depth:
- Dermal-epidermal;
- Dermal;
- Dermal-Subdermal;
- Subdermal.
FAQ
1. What are morphological elements without cavity?
These are primary manifestations of skin diseases that arise on previously unchanged skin and mucous membranes without cavities being formed. They represent dense formations or changes in skin coloration.
2. Why do hemorrhagic macules not disappear when pressed upon?
They are caused by the extravasation of blood from vessels into the tissues. Therefore, they do not blanch during diascopy and retain their color. Examples include petechiae, purpura, and ecchymoses.
3. How do a macule and a patch differ?
A macule is a spot up to 1 cm in diameter; a patch is larger than 1 cm. This distinction is conventional and is used to clarify the size of the lesion.
4. What is the difference between a papule and a nodule?
A papule (papula) is a superficial lesion up to 1 cm in diameter. A nodule (nodus) is a deep, firm lesion measuring 1 cm or more, which may be located in the dermis or subcutaneous tissue and often leaves a scar after ulceration.
5. Can a nodule be a benign lesion?
Yes, it can. For example, in lipoma or an intradermal nevus, a nodule may be benign and not cause inflammation.
6. Why is it important to distinguish types of primary lesions?
The type of morphological element helps the clinician establish a preliminary diagnosis, assess the nature of the process (inflammatory, neoplastic, vascular), and choose an appropriate treatment strategy.
References
1.
VOKA 3D Anatomy & Pathology – Complete Anatomy and Pathology 3D Atlas. VOKA 3D Anatomy & Pathology.
Available from: https://catalog.voka.io/
2.
Carter KF, Dufour LT, Ballard CN. Identifying primary skin lesions. Nursing. 2003 Dec;33(12):68-69.
3.
Burgin S. An approach to primary lesions. In: Burgin S, ed. Guidebook to dermatologic diagnosis. McGraw-Hill Education; 2021. Accessed 2025 Apr 1.
4.
Mowlabaccus WB. Common benign skin lesions [Internet]. DermNet; 2020.
Available from: https://dermnetnz.org
5.
Soutor C, Hordinsky MK, eds. Clinical dermatology: diagnosis and management of common disorders. 2nd ed. McGraw-Hill Education; 2022.
6.
Hunter JAA, Savin J, Dahl MV. Clinical dermatology. 3rd ed.
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