Module 3 - Skin & Soft Tissue Lesions

Treatment

For Skin Lesions:

i.) Shave biopsy

When full-thickness excision of the lesion is unimportant, shave biopsy is used to remove an elevated lesion. Thus, it is ideal for elevated benign nevi, as it minimizes scarring, but inappropriate for melanoma, where full-thickness is crucial for diagnosis and prognosis.

The area is first frozen with lidocaine and then a surgical blade is drawn across the lesion in broad strokes to remove elevated tissue. This can leave a jagged surface, but can be smoothed out with electrocautery.

ii.) Punch biopsy

Cylindrical dermal punch tools of varying diameter (2 mm, 3 mm, 4 mm) are available to acquire a sample with a full-thickness of skin for analysis and leaving minimal scarring to the patient. This procedure is appropriate for most skin lesions except suspected melanoma cases, where complete excision of the lesion with normal margins should be performed. The site is prepared with 1% lidocaine and epinephrine and the surrounding skin stretched and supported during the incision with the punch blade. When the punch blade is withdrawn, a cylinder of tissue is produced and scissors or a scalpel blade are used to completely excise the tissue from the site. The sample is then placed  in formulin for pathology and the biopsy site sutured or bandaged as needed.

iii.) Excisional biopsy

Complete excision is the best treatment for a potential melanoma as full-thickness is required for accurate diagnosis using Breslow’s scale. The margin of normal tissue excised with the malignant lesion depends on tumour thickness.

iv.) Moh’s Micrographic surgery

Horizontal sections of tumour tissue are excised allowing all of the surgical margins to be examined and the maximal preservation of normal tissue. This excisional technique is indicated for BCC, where the tumour often has finger-like projections extending into normal tissue. Because each thin excision must be fixed, dyed and examined microscopically, this is a very time-consuming procedure requiring hours or days to perform. It is only performed at specialized centres.

v.) Electrodesiccation and Curettage

ED&C is indicated for the removal of superficial skin lesions, BCC and SCC. Sharp dermal curets are employed to scrape or scoop out the lesion or tumour tissue while an electrode attached to an electrodesiccation unit is used to control bleeding and eliminate any remaining fragments of abnormal tissue. A disadvantage of this procedure is the fact that electrodesiccation is known to result in more hypopigmentation and scarring.

vi.) Cryotherapy

Involves freezing the lesion with liquid nitrogen, either using a sterile contact probe or direct spray, and repeating freeze thaw cycles to maximize tissue damage. This can be a quick and effective treatment for small, superficial, non-malignant lesions. Freezing deep lesions can result in significant pain for the patient.

vii.)  Sentinel Lymph Node Dissection

SLN biopsy is appropriate for melanomas deeper than 1.0mm and for tumors 1mm or less when histologic ulceration is present and/or classified as Clark level 4 or higher. On the day of surgery, tumour tissue is injected with technetium (T99) to be taken up by lymphatic vasculature draining the tumour area. The T99 drains first to the sentinel node and then to the remaining regional nodes. The tumour site is also injected with lymphazurine 1% blue dye which is also taken up by the sentinel node. Because the sentinel node is the first site of drainage, T99 and lymphazurine are concentrated there, facilitating identification and removal of the SLN. Pathological examination of this tissue will determine tumour spread. If positive, regional lymph node dissection is performed as well as other investigations for tumour spread to other areas of the body.

 

For Soft Tissue Lesions:

i.) Fine-needle aspiration (FNA)

Using a narrow gauge needle on a 10 ml syringe, multiple passes are made through the mass in various directions to collect a sufficient tissue sample. The specimen is immediately fixed and sent to pathology. Although this collection method does not allow for the tumour mass to be graded, the presence of malignancy can be determined along with histological tumour type. Thus, despite being the least invasive diagnostic technique, it is also the least informative. Also, the rate of false-negatives with this technique is about 10% and should be verified with incisional or excisional biopsy. The rate of false-positives is very low.

ii.) Core-needle biopsy

After a small incision is made, the core biopsy needle is inserted into the skin until it reaches the tumour mass. The needle is then opened so that the inner trocar proceeds further into the tumour and, with manual stabilization, a sample is excised from the mass as the outer sheath closes over the inner trocar. The core of tissue obtained is immediately placed in formalin. Usually, several passes are made. If a good core sample is obtained, the information drawn from it can equal that found with an incisional biopsy. As with FNA, the rate of false-positives is very low, but false-negatives should be verified with incisional or excisional biopsy.

iii.) Incisional biopsy

This procedure is usually performed in an operating room under anaesthesia. It is generally recommended for tumours greater than 3 cm in diameter or where excisional biopsy is not indicated, as is the case with suspected sarcomas or for reasons of cosmetic impairment in regions such as the scalp or face. Drains should be avoided with this procedure and meticulous hemostasis must be performed to prevent tumour spread.

iv.) Excisional biopsy

Performed for tumours that are likely benign or less than 3 cm in diameter. An elliptical incision is made around the tumour along the lines of minimal skin tension excising the tumour in its entirety along with a margin of normal tissue. The incision should be made into subcutaneous tissue but not penetrate the fascia or deeper structures. Primary closure with layered suturing follows with samples fixed and sent to pathology.

 

Imaging for Soft Tissue Masses

    CT (Computed Tomography)

Used for larger, deeper tumours to assess the character and extent of tumour, the involvement of other structures and to determine surgical access to the site. Can employ CT-guided core-needle biopsy for deep tumours at surgically inaccessible sites.

    MRI (Magnetic Resonance Imaging)

Better imaging technique than CT for soft tissue tumours, however it is difficult to distinguish tumour tissue from edema.

    Angiography

    Useful when tumours are proximal to or impinge on major vessels. Better as an adjunct imaging technique than for primary imaging.


Author: SP Zinn