Showing posts with label Punch biopsy. Show all posts
Showing posts with label Punch biopsy. Show all posts

Punch biopsy


What is punch biopsy?
Punch biopsy is one of the most widely used dermatologic procedures in primary care medicine. This technique obtains a full-thickness skin specimen for histologic assessment. A properly performed punch biopsy frequently yields useful diagnostic information. The technique is simple, rapid, and generally results in an acceptable final cosmetic appearance at the site.

What are the indications of punch biopsy?
Evaluation of skin tumors, diagnosis of skin disorders, removal of small skin lesions such as intradermal nevi and diagnosis of atypical appearing lesions.

How is punch biopsy performed?
Punch biopsy is performed with a circular blade known as a trephine, which is attached to a pencil-like handle. The instrument is rotated using downward pressure until the blade penetrates into the subcutaneous fat. A cylindrical core of tissue is then cut free and placed in formalin for transfer to the laboratory. Most 3- or 4-mm punch biopsy sites are closed with a single suture. The 2-mm punch biopsy sites frequently do not require suture closure, and Monsel's solution can be used for hemostasis if the wound is allowed to granulate.

Why is punch biopsy performed?
Punch biopsy is generally performed to evaluate lesions of uncertain origin or to confirm or exclude the presence of malignancy. This biopsy technique is considered the method of choice for many flat lesions. Suspected melanomas can be evaluated by this technique, especially when the lesion is too large for easy removal. The yield may be improved if the most suspicious or abnormal-appearing area (darkest, most raised, or most irregular contour) is biopsied. If the suspicion for melanoma is high, it is preferable to perform excisional biopsy to have the entire lesion available for evaluation.

What are the disadvantages of performing punch biopsy for suspected cancer lesions?
Punch biopsy used for basal and squamous cell carcinoma has one disadvantage. After these cancers have been biopsied using punch technique, the physician is obligated to perform a definitive excisional technique. Superficial techniques that are frequently employed for these lesions, such as curettage and electrodesiccation, may miss cells that have been driven deeper by the punch instrument. Physicians should not fear performing punch biopsy on a melanoma, because the biopsy does not alter the natural course of the disease, and a prompt biopsy expedites definitive treatment.

What should physicians be oriented of when performing a punch biopsy?
Physicians should be aware of the underlying anatomy when performing a punch biopsy. Certain areas of the body where there is little subcutaneous tissue pose the greatest threat of damaging underlying structures such as arteries, tendons, or nerves. Punch biopsy on the upper cheek can damage the facial or trigeminal nerves, and punch biopsy of the lateral digits or of the thin eyelids should be approached with great caution.

What are the implications of these factors on performing a punch biopsy?
Lesions overlying anatomic structures likely to be damaged by full-thickness skin biopsy: on the eyelid (globe), on the dorsum of the hand in elderly patients (tendons), or on the upper cheek (facial nerve) or fingers (digital nerves and arteries) should be contrindicated. Also foot and toe lesions in elderly patients or those with peripheral vascular disease.

 

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Skin Biopsy

Skin moles can be surgically removed for cosmesis or biopsied because of concern regarding the cancerous potential of a mole. A skin biopsy can be performed simply in the doctor's office. Several techniques are practiced, and each has specific advantages. Pigmented lesions suspicious for melanoma should be removed completely. This is best done by complete excision. We only do shave biopsies on such lesions if we are certain that the deepest portion of the lesion will be removed. Both shave and punch biopsies result in a scar. Benign lesions are only removed if the patient understands that a permanent scar will result.

skin moles removed for cosmetic considerations are often removed by shave excision. Punch excision can be used for relatively small moles. Large moles may require complete excision with sutured closure, because moles exceeding 1 cm in diameter often are not amenable to the shave technique. A simple conservative excisional biopsy with a sutured closure is usually the most speedy means to diagnosis if concern exists regarding the possibility of melanoma. If the mole is found to be benign, then, ordinarily, no further treatment is required.

Providing the pathologist with a complete excisional specimen affords the best opportunity to make an accurate diagnosis because all available criteria (including gross features such as size, circumscription, and symmetry) can be applied to the mole. Interpreting partial biopsy samples of melanoma is not wise, especially for pathologists with limited experience in the microscopic evaluation of melanocytic neoplasms; not uncommonly, it can lead to a false diagnosis of a mole. If a biopsy specimen represents a partial sample of a larger mole, the clinician should clearly indicate this to the dermatopathologist or pathologist on the requisition form. If any atypical feature is present, a second opinion from an expert dermatopathologist should be pursued.

Punch biopsy
A full thickness of skin can easily be obtained with a cylindric dermal punch biopsy tool. Disposable punches are very convenient (e.g., the Baker-Cummins punch). They are available in 2-mm, 3-mm, 3.5-mm, 4-mm, and 6-mm widths. The 3-mm punch is adequate for most lesions. Biopsies of the face may be peformed with a 2-mm punch to minimize scarring. The resulting wound has smooth, round edges and heals with a slightly depressed scar.
The procedure is adequate for the diagnosis of most tumors. If possible, lesions suspected of being malignant melanoma should be removed completely intact with an excisional biopsy.
Suturing round or oval defects produced by the punch has been advocated by some authors, but suturing does not lead to satisfactory approximation of the margins. Healing by secondary intention is slow but cosmetically acceptable.
Punch biopsy technique.
The site is prepared for biopsy with an alcohol pad; a sterile technique is not required. Local anesthesia is induced with 1% lidocaine with epinephrine. Epinephrine is avoided for biopsy near the fingertips. The injection is positioned around and under but not directly into the lesion.
The surrounding tissue is supported by stretching the skin with the thumb and index finger of the free hand. The punch is rotated back and forth between the thumb and forefinger while it is simultaneously pushed vertically into the tissue. Resistance is felt while the instrument penetrates through the dermis but ceases as the punch sinks quickly on entry into the subcutaneous tissue.
The punch is withdrawn and the cylindric piece of tissue is gently supported with smooth-tipped forceps; the specimen is cut deep with scissors to include subcutaneous tissue. Forceps with teeth may crush the specimen.
The tissue is immediately transferred to a preservative, and bleeding is controlled with Monsel's solution.

Shave biopsy
Shave biopsy and shave excision are useful for elevated lesions and when a full thickness of tissue is unimportant. Shave excision of nevi produces excellent cosmetic results. Any pigmented lesion suspected of being a melanoma should be totally removed by excisional biopsy.
Shave technique.
The lesion is elevated from the surrounding skin by infiltration with lidocaine. The surrounding skin is supported with the thumb and forefinger of the free hand. The flat surface of a #15 surgical blade is laid against the skin next to the lesion. With long strokes, the blade is smoothly drawn through the lesion; back-and-forth sawing motions produce a jagged surface. Several strokes may be required around the periphery of larger lesions. The last attachment of skin may be severed more easily with scissors than with a scalpel blade. Rough edges and contours can be smoothed with electrocautery, and bleeding can be controlled with Monsel's solution.

 

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