Imaging Studies
MRI is a useful primary step in differentiating plantar fibromatosis from surrounding tissue. Images show some signal intensity heterogeneity and, usually, infiltrative margins. [8] MRI can show the degree of deep invasion of the plantar fibromatosis, which often reaches the aponeurosis. [9]
The MRI signal intensity and the consistency of the clinical location of Ledderhose disease enable the diagnosis to be made with reasonable confidence. However, one must consider the diagnosis of clear cell sarcoma in the differential. In effect, the 2 entities can have similar MRI findings and clinical locations.
For fluorine-18 fluorodeoxyglucose (FDG) imaging, see Scheler et al. [10]
Histologic Findings
All types of plantar fibromatosis have a dense fibrocellular tissue with mature collagen and fibrocytes in various stages of maturation, but they do not have prominent atypical features or abnormal mitotic activity. The overlying epidermis and superficial dermal tissue are usually normal, but the neoformation, which grows upward and downward, generally replaces the adipose tissue. The proliferation often involves many cellular foci surrounded by fibrous scarlike connective tracts.
In superficial plantar fibromatosis, the limits are usually undefined. Some areas may be almost acellular, with a scarlike appearance. In other areas, or in the most active early cases, the fibrocytic component can be dense, with cells closely packed together; the differential diagnosis with fibrosarcoma can be difficult in these cases. The reticulin network is often prominent. Usually, inflammation-associated infiltrate is not present. The connective stroma may involve various aspects. The stroma may be dense and fibrous; less commonly, it is loose. Sometimes, myxoid or chondroid areas can be seen. Vascularization is not a prominent feature. Local nerves and Vater-Pacini corpuscles can seem to be increased in number or size.
In juvenile aponeurotic fibroma, the cells are round or oat-shaped, and the stroma is chondroid (cartilage analogue fibromatosis). Aggressive forms are usually more cellular and have increased mitotic activity. Peripherally, the proliferation is poorly limited and penetrates the neighboring structures. Hamartomatous cerebriform plantar fibromatosis has a variable fibromalike, lipomatous, angiolipomatous, or combined structure.
The myofibroblast is the key proliferative cell in some so-called fibromatoses; therefore, these might be better named myofibromatoses. In these fibromatoses, results of tests for cytologic markers in muscle cells are positive.
In recurrent plantar fibromatosis, as in aggressive fibromatosis, tumoral cells express platelet-derived growth factor-B (PDGF-B) proto-oncogene. [11] This proto-oncogene encodes the B chain of PDGF-B, a mitogen for fibrocytes, whereas normal plantar fascia, nonrecurrent plantar fibromatosis, and scars do not. Thus, the detection of PDGF-B may be a useful adjunct to the pathologic evaluation of invasive plantar fibromatosis for prognostic purposes.
Osseous metaplasia and distinct multinucleate giant cells have been reported in Ledderhose disease. [12, 13]
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Superficial fibromatosis of the heel.
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Juvenile aponeurotic fibroma.
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Hamartomatous fibromatosis.
