Cancer is a disease where cells grow uncontrollably and can spread to other parts of the body. Normally, cells grow and die in an orderly fashion; in cancer, this process breaks down due to genetic changes. Dermatofibrosarcoma Protuberans (DFSP) is a rare soft tissue sarcoma, a cancer developing in connective tissues like fat, muscle, and skin.
Understanding DFSP
DFSP is a rare skin cancer originating in the dermis (the skin’s middle layer). It arises from fibroblasts, cells found in the dermis’s connective tissue. Characterized by slow growth, it is locally aggressive, infiltrating surrounding tissues like fat, muscle, and bone. Despite its aggressive local nature, DFSP rarely spreads to distant parts of the body. It accounts for approximately 1% to 6% of all soft tissue sarcomas and affects about 4 out of 1 million people worldwide each year, making it an uncommon diagnosis.
DFSP typically appears on the trunk (chest, back, shoulders, abdomen, buttocks) and extremities. Though it can occur anywhere, including the head and neck, it is less frequent there. The tumor often presents as a firm, raised patch or nodule. In many cases, a specific genetic change—a translocation between chromosomes 17 and 22—leads to the fusion of COL1A1 and PDGFB genes. This fusion results in the overproduction of a growth factor, promoting uncontrolled cell proliferation.
How DFSP Presents
DFSP often begins as a small, firm patch of skin feeling rubbery or hard. This initial patch may resemble a bruise, a birthmark, or a deep-seated pimple. It is often discolored, appearing reddish-brown, purplish, or flesh-toned. The lesion grows slowly, often over months or years, which can delay detection.
As the tumor grows, it may become a raised lump or nodule, pushing into the skin’s top layer. These protuberant masses can be firm or rubbery and may appear fixed to the skin. DFSP is often painless in its early stages. Pain, tenderness, bleeding, or ulceration may develop as the tumor grows larger or becomes more advanced, though this is less common.
Diagnosing DFSP
Diagnosing DFSP begins with a physical examination, where a healthcare provider examines any suspicious lumps or patches. This initial assessment is crucial, as the tumor’s slow growth often leads to delays in diagnosis. Imaging studies assess the tumor’s size, depth, and relationship with surrounding structures like muscles, nerves, and bones. Magnetic Resonance Imaging (MRI) often provides detailed images to determine the tumor’s extent.
A definitive diagnosis requires a biopsy, taking a tissue sample from the suspicious area. This sample is then examined under a microscope by a pathologist. The biopsy helps confirm the presence of cancer cells and differentiates DFSP from other skin conditions that may look similar. Pathological examination identifies specific cellular characteristics, such as spindle-shaped cells in a “storiform” or “cartwheel” pattern, and confirms the characteristic COL1A1-PDGFB gene fusion, which guides treatment decisions.
Treatment Approaches for DFSP
The primary treatment for DFSP is surgical excision, aiming to remove the entire tumor with clear margins. Due to DFSP’s infiltrative nature, often extending beyond what is visibly apparent, wide local excision is commonly performed. This procedure involves removing the tumor with a surrounding margin of seemingly healthy tissue (typically 2-3 centimeters) to minimize recurrence risk. Achieving clear margins is important, as positive margins significantly increase the risk of recurrence.
Mohs micrographic surgery (MMS) is an effective surgical technique for DFSP, especially for tumors in cosmetically sensitive areas like the head and neck. MMS involves removing the tumor layer by layer, with each layer immediately examined under a microscope to ensure all cancer cells are removed before the procedure concludes. This precise method maximizes cancerous tissue removal while preserving healthy tissue, leading to a very low local recurrence rate, often approaching zero percent when performed effectively.
Radiation therapy may be used when surgical margins are positive or complete surgical removal is not feasible due to tumor size or location. It can help reduce the risk of local recurrence by targeting any remaining cancer cells. For advanced or unresectable DFSP, targeted therapy with the drug imatinib is an option. Imatinib targets the COL1A1-PDGFB gene fusion, which drives most DFSP tumor growth, and can shrink the tumor, sometimes enabling surgical removal.
Living with DFSP
Following DFSP treatment, long-term follow-up and monitoring are important due to possible local recurrence. Recurrence can happen many years after initial treatment, with many instances occurring within the first three years post-surgery. Regular check-ups, often every 6-12 months initially, are recommended to detect any signs of recurrence.
The prognosis for DFSP is favorable, particularly with complete surgical removal. The 10-year survival rate is high, around 99.1%. While local recurrence is the most common concern, distant spread is infrequent. Vigilance through consistent self-examination and scheduled medical evaluations helps ensure early detection and management of recurrences.