Sarcomas of the Skin

 

Dermatofibrosarcoma protuberans (DFSP) is a fairly uncommon, low-grade skin cancer that can be difficult to cure.  Like most skin cancers, it is not caused by solar radiation, but instead is caused by an accidental rearrangement of DNA in a gene. It affects people of all races, but it is somewhat more common in those with more darkly pigmented skin.  DFSP occurs most commonly in the young and middle-aged, from 18-55 years old.

Dermatofibrosarcoma protuberans arises in the second layer of skin, the dermis, and can spread to much deeper structures including the subcutaneous fat, muscle, and even bone.  It metastasizes (spreads internally through lymph nodes or the blood stream) in a very low number of cases, and generally only after the tumor has become very large.  A typical presentation of DFSP is that of a firm knot under the skin that grows very slowly.  It may form a scar-like lesion on top of the skin.  In time, large aggressive tumors can form.

Treatment is complete surgical removal.  The problem with DFSP is that it forms roots like tentacles that spread very much wider and deeper than can be seen with the eye.  Wide surgical excision can miss these roots resulting in recurrence in a high number of cases (16-50% in different studies).  Failure to clear the tumor can lead to these tumors recurring as very large, deep tumors that can pose extreme problems.  By contrast, Mohs surgery has recurrence rates that are dramatically lower, on the order of 2%.  For this reason, Mohs micrographic surgery is now considered the treatment of choice for DFSP.

 

Atypical Fibroxanthoma (AFX) is a common tumor that appears in older patients in heavily sun-exposed areas. It appears most often on the scalp, face and neck in older, fair-skinned men. AFX arises quickly and ulcerates to form a red, bleeding nodule. It can be confused with other types of skin cancer and a biopsy to exclude other types of cancer is the only way to make the diagnosis. AFX is thought to be a superficial variant of the more aggressive malignant fibrous histiocytoma . Fortunately, despite the ominous appearance of this cancer, it rarely metastasizes (spreads internally through lymph nodes or the blood stream), perhaps because it is usually cured surgically before allowed to spread. Inadequately treated or deeper lesions can become deadly, but htis is rare. Mohs micrographic surgery is often used to clear margins and keep the wound small, but simple wide surgical excisions is also effective. 

Malignant Fibrous Histiocytoma is the most common type of cancer that forms in the soft tissue. It is generally found on areas such as the upper legs, arms or abdomen. It has been found to develop in areas of the body where radiation therapy was given in the past.  Malignant fibrous histiocytomas often grow quickly and spread to other parts of the body, including the lungs. 

Leiomyosarcoma is an uncommon tumor of smooth muscle fibers.  It can begin in muscle cells inside the body, in which case it can be a very aggressive cancer.  If it arises from the skin, leiomyosarcoma is almost always curable because patients notice them and they are treated before they can become large and dangerous.  Leiomyosarcoma of the skin arises from the smooth muscle fibers known as the arrector pili muslce that attaches to the hair follicle.  The cause of this cancer is unknown, and probably not sun related.  Leiomyosarcoma usually presents as a firm bump just under the skin that can be painful to the touch.  These usually occur on the lower legs and arms, but can appear anywhere.  If caught early, these tumors are very curable.  Occasionally these tumors metastasize (spread internally through lymph nodes or the blood stream), especially if they have been allowed to grow to large size before treatment. The best treatment is surgical excision, and Mohs micrographic surgery is often recommended.

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