Soft Tissue Tumors in Children and Adolescents:
A Morphologic Pattern Oriented Approach with Molecular and Genetic Correlations
Section 6 -
Gardner Fibroma and Desmoid Fibromatosis
Cheryl M. Coffin, M.D.
David M. Parham, M.D.
A 12-year old boy developed a painful enlarging nodular and plaque-like mass in the superior
paraspinal region. He had a history of superficial soft tissue masses in the paraspinal region, head,
chest wall, and posterior thigh since two years of age. Biopsies in the past had revealed benign fibrous
lesions, including one from the same site. The family history was remarkable for rhabdomyosarcoma in a
paternal uncle at 3 years of age, desmoid tumors and colonic adenomas in the father, and colonic
adenocarcinomas in paternal relatives. Genetic testing of the child and his father revealed an APC mutation.
Discussion and Differential Diagnosis:
This case is an example of Gardner fibroma with development of a desmoid fibromatosis in the same
site, in a patient with APC. The points for discussion are the clinicopathologic features and
differential diagnosis of Gardner fibroma and desmoid tumor, the association with APC, and manifestations
of APC in childhood and adolescence.
The rubbery plaque-like areas of the mass showed typical features of Gardner-associated fibroma with
hypocellular sheets of haphazardly arranged collagen fibers separated by clear cracks and bland spindle
cells. The Gardner fibroma entrapped adipose tissue, blood vessels, and nerve fibers.
Immunohistochemistry revealed reactivity for CD34 in the bland spindle cells. The round nodular area
showed histologic features of desmoid fibromatosis with interlacing bundles of uniform spindle cells
separated by variable collagen and delicate curing blood vessels. The spindle cells had oval to
elongated nuclei, abundant cytoplasm, and indistinct cell borders. In some areas, the tumor cells had a
more plump stellate configuration, and myxoid foci were present. There was variable immunohistochemical
reactivity for smooth muscle actin. Occasional mitoses were seen, but no atypical mitoses were
Gardner fibroma is a distinctive, densely collagenized, sheet-like proliferation of bland spindle
cells. It entraps normal tissues, such as fat nerve and blood vessels. Frequently it is an early
manifestation of familial adenomatous polyposis and may be associated with classic desmoid fibromatosis,
as in this case. It occurs in superficial and deep soft tissues of the trunk, head and neck, and
extremities. Gardner fibroma in childhood can serve as a sentinel event for identifying an individual or
a family with adenomatous polyposis coli.
Desmoid tumor accounts for up to 60% of fibrous tumors of childhood, although it has traditionally
been considered an adult-type fibromatosis. There is a well-established association with familial
adenomatous polyposis (FAP, Gardner syndrome) and with antecedent trauma, surgery, and irradiation. A
desmoid fibromatosis in early childhood may be the initial manifestation of an APC mutation or may occur in the same site as a pre-existing or concurrent Gardner
fibroma. The firm, grey-white, oval or fusiform mass has irregular infiltrative margins and a white,
whorled, or trabeculated cut surface. There is limited information to suggest that foci of mucoid
degeneration, abundant plump stellate tumor cells, and a large number of small slit-like blood vessels in
the central portions of the tumor may be associated with a higher tendency for recurrence. The local
recurrence rate is 33 to 68%. The advancing border of the tumor infiltrates between and entraps adjacent
tissue, and chronic inflammation may be seen at the periphery. It is usually very difficult to determine
the surgical margins at the time of operation. Desmoid fibromatosis is a clonal neoplasm which may
harbor trisomies 8 and 20 and 5q deletion in addition to APC mutation.
The differential diagnosis includes fibromatoses, keloid or hypertrophic scar, nuchal fibroma,
infantile myofibromatosis, nerve sheath tumors, inflammatory myofibroblastic tumor, and low-grade spindle
cell sarcomas such as myofibrosarcoma and low-grade fibromyxoid sarcoma. In most instances the
distinction can be made on the basis of histopathology and immunohistochemistry.
This case highlights the association between FAP and Gardner fibroma and emphasizes that Gardner
fibroma can be the sentinel event for the diagnosis of adenomatous polyposis coli in a child and family
members. In FAP the average onset of intestinal adenomas is 25 years and the lifetime risk of intestinal
adenocarcinoma is 100%. Extracolonic manifestations of adenomatous polyposis coli seen in children
include gastrointestinal, soft tissue, and other types of lesions. In the gastrointestinal tract,
tubular adenomas are characteristic and additional lesions include hyperplasia, hamartomas,
adenocarcinoma, carcinoid tumor, and hepatoblastoma. In the soft tissue, fibromas and desmoid tumor are
the most frequently encountered lesions, but there is an increased frequency of rhabdomyosarcoma in
families with APC mutation. Nasopharyngeal angiofibroma may also be
associated with FAP. Other lesions encountered in children with APC
mutations include epidermoid cysts, osteomas, brain tumors, thyroid carcinoma, dental abnormalities, and
congenital hypertrophy of the retinal pigment epithelium.
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