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      When one hears the word "BIOPSY", visions of cancer cannot be avoided.  One thinks of breast biopsy, for example, and it is hard not to think of cancer as a possible finding.  In the foot, biopsy can take many forms.  There is biopsy of skin, biopsy of deeper soft tissue, fine needle aspiration of cysts and other fluid-filled masses, and in some cases bone biopsy.  Today - we are going to talk about the biopsy of the SKIN and other skin-like structures, such as NAIL or NAIL BED TISSUE.  While biopsy of the skin of the foot is done to rule out potential malignancies, such as basal cell carcinoma, squamous cell carcinoma, and malignant melanoma, there are many other reasons to biopsy.  

     Skin biopsy of the foot can be done to find out why the skin is discolored and/or dry and scaly.  Fungal infections, such as Athlete's foot, are often misdiagnosed.  A red, itchy, and dry/scaly area on the foot is not always fungus!   While dry and scaly red skin on the bottom of the foot, and extending into the web spaces (area between the toes) is probably fungal, there are other causes.  Bacterial infections can infect this area also.  Allergic reactions to things touching the skin (contact dermatitis), atopic dermatitis, psoriasis, eczema, and other non-infectious skin problems are much more common than fungus when the top, or dorsal aspect of the foot is involved.  Parasitic infections, including scabies and creeping eruption (larva migrans) can also cause severe itching, redness, and changes in the skin that may make one think there is a fungus.  Antifungal medications will have NO EFFECT on such conditions.  Making things even more interesting, it is possible to have a fungal infection between the toes that gets SECONDARY INFECTION with bacteria..  In this case, a culture of the drainage, along with a biopsy and/or culture for fungus is very beneficial.  A WOOD'S LAMP or ultraviolet light examination can also help. Skin biopsies in cases of red/itchy/dry skin can save the patient time and money in that a definitive diagnosis is made and there is usually no need to keep switching medications from antifungals - to steroids (cortisone type creams) - to another steroid - to a mixed steroid and antifungal.  You know which medication to use as soon as the biopsy report comes back.

   Skin biopsy can also be done to determine the diagnosis of a skin "tumor" when it is not certain by visually examining it, or when conservative treatment does not work.  Warts, for example, are very common on the bottom of the foot (PLANTAR WARTS).  These are often treated with cryotherapy (freezing), chemical cauterization with acid, electrical cauterization (Hyfrecation) or with a laser.  None of these, however, gives a specimen for microscopic examination.  If a wart-like lesion does not respond to these treatments, or it comes back again and again, a biopsy is indicated.  In many cases, sutures are not needed, expecially if the lesion is small.  Other things can look like warts - such as an IPK (very deep corn), porkeratosis (blocked sweat duct causing a wart like lesion), and foreign bodies (a small splinter or piece of glass can feel much like a wart).  Biopsy of one of these lesions is very helpful in determining the course of treatment.  If a lesion is treated as a wart, for example, and it is actually an IPK or corn, the problem will keep coming back because it is not a problem within the skin.  Such lesions are due to PRESSURE, and can be caused by a bone spur, accessory or extra bone, prominent metatarsal bone, or even the way the foot functions.  People with excessive pronation or flat feet often get a deep corn or IPK beneath the 2nd metatarsal head.  I have seen MANY cases where these were treated as warts - with freezing, acid, surgical removal, even skin grafting, and continual recurrence,  If the lesion had been biopsied, the microscopic exam would have shown that the layer of skin that is thickened is NOT what is seen with a wart, and that all of these treatments are futile.  Using a custom orthotic device or arch support would help to eliminate the pressure, and possibly eliminate the lesion altogether!  

    Bleeding under the nail - often referred to as "Tennis toe" and properly called a SUBUNGUAL HEMATOMA is a very common condition.  This is seen in very active people such as runners, tennis players, and other athletes.  It is due to pressure and friction of the nail against the nail bed or skin under the nail.  On the other hand, it can also be seen on older adults on blood thinners such as Coumadin or even aspirin.  A single traumatic event, such as dropping something on the toe, can also cause hemorrhage under the nail and it gets trapped and cannot come out.  The problem is that while 99+% of these "dark areas under the nail" are BLOOD, it is also possible to get a melanoma under the nail.  Melanomas are very serious, highly malignant lesions, typically non-painful, and cannot always be differentiated from blood just by looking at it.  Doing a punch biopsy, to remove a portion of the nail and some of the nail bed beneath it, is an excellent way to tell if the problem is just blood or a potentially fatal melanoma.  Nail unit biopsy can also be done in cases of suspected nail fungus, where the thickening and discoloration of the nail is not responding to medication, laser treatment, or other conservative measures.  Trauma to the nail can result in thickening and discoloration, and if there is no fungus present, topical antifungakl medication, oral antifungal medication, and laser will not work.  The nail may have to be removed.   I have also seen patients with psoriatic nails.  Psoriasis can cause abnormal looking toenails, and while they will often have "pits" or little holes in the nail, sometimes the nails just look thick and discolored with debris under the nails.  Some patients don't even know they have psoriasis, and again the use of medications for fungus will not help them.  Laser treatment may have some benefit in these patients, but they certainly will not respond the same way that fungus nails respond to laser. 

    Once again, biopsy of the skin on the foot can be used to confirm or rule out the presence of a malignant condition.  It must be understood however, that there are many other reasons that a biopsy of that thickened, discolored, dry, or wet skin or nail may be needed.  While most dermatologists, and many podiatrists do perform skin biopsy on the foot, this is one diagnostic tool that is NOT done often enough!   When the diagnosis of a skin or nail problem is questionable, or the problem just is not responding the way it should be responding, ask your doctor to do a biopsy.  

      

   

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