[5] In the majority of cases,[6] GF tumors are manifestations of the genetic disease, familial adenomatous polyposis (FAP), or its variant, the Gardner syndrome (GS).
[9] However, some cases of sporadic GF and DT will, over the ensuing months or years, present with other signs of, and be diagnosed as, FAP.
[1][2][10] GF tumors typically present as a single but in some cases multiple plaques (i.e. papule-like masses that are 10 mm or more in longest diameter)[6] located on the skin of the back or, less commonly, head, neck, extremities, or abdominal regions.
[1] GF plaques on the skin are generally white, rubbery,[9] painless masses[6] that occur mainly in children during the first decade of life[9] but have also been diagnosed in adults as old as 59 years.
[9] The majority of individuals presenting with GF tumors have or will develop FAP due to mutations in the APC gene.
Partially or totally inactive APC protein in FAP allows the excessive intracellular accumulation of β-catenin and thereby promotes development of the tumors, cancers, and other manifestations of this disease.
[13] The central feature of FAP is the formation over time of an increasing number of adenomatous polyps (i.e. abnormal growths of tissue projecting from a mucous membrane that have a high potential to become cancerous) in the colon and rectum.
Slit-like empty spaces and loci of adipose tissue and/or skeletal muscle may also be imbedded in the collagen bundles.
The outer edges of these tumors may entrap peripheral nerve fibers and blood vessels and may infiltrate into otherwise normal subcutaneous fat tissues.
[7] The diagnosis of GF depends on: its clinical presentation, i.e. occurrence as solitary plaque-like skin lesions that are located in the dermis of children; patient histories of previously having a GF tumor that was surgically removed;[1][15] characteristic histopathology findings;[3] tumor cell expressions of CD34[15] and β-catenin proteins[2] but not smooth muscle actin;[13] and the presence of other lesions associated with FAP, a family history of FAP, and/or family members with a history of FAP-like lesions.
[7] Individual cases of highly aggressive, symptomatic, and/or repeatedly recurring tumors diagnosed as DT but likely including GF-DT tumors have been treated with nonsteroidal anti-inflammatory drugs, antiestrogens (e.g. tamoxifen: desmoid tumor cells express estrogen receptors), radiation therapy, tyrosine kinase inhibitors (e.g. imatinib[16]), and chemotherapy (i.e. multiple drug regimens such as vinblastine combined with methotrexate, doxorubicin combined with dacarbazine, or adriamycin combined with dacarbazine or single drug regimens such as doxorubicin, methotrexate, vinorelbine, or metronomic, i.e. low-dose, long-term treatment, etoposide or cyclophosphamide).
[16] Additional recommendations for individuals diagnosed with Gardner fibromas include: 1) long-term follow-ups to check for recurrent disease and the development of other FAP lesions;[1] 2) genetic counseling;[2] 3) mandatory screening (e.g. colonoscopy) for FAP every 6[10] or 12 months;[14] and 4) surveillance of the individual's parents, siblings, and children for the presence and development of FAP-associated lesions.