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Myxoid dermatofibrosarcoma protuberans: clinicopathologic,
immunohistochemical, and molecular analysis of eight cases.Am
J Dermatopathol. 2007 Oct;29(5):443-8.
Dermatofibrosarcoma protuberans (DFSP) represents a locally
aggressive mesenchymal neoplasm of skin and subcutis with
characteristic clinicopathologic, immunohistochemical, and molecular
findings. In addition to typical cases, morphologic variants such as
pigmented, fibrosarcomatous, myofibroblastic, and granular cell DFSP
have been described. Purely or predominantly myxoid DFSP is
extremely rare, and may cause considerable diagnostic problems.
Eight cases of predominantly myxoid DFSP were studied.
Paraffin-embedded blocks and slides were retrieved from the files of
the authors. Clinical data were obtained from the referring
pathologists and dermatologists. Immunohistochemistry was performed
using the ABC method, and three cases were studied by polymerase
chain reaction technique. There were six male and two female
patients (age range: 29 to 74 years). Locations included the
inguinal area (three cases), thigh, upper arm, shoulder, abdominal
wall, and back (one each). The patients were treated by wide
excision as well as reexcision. Tumor size ranged from 1.5 to 12 cm.
Histologically, a nodular growth with peripheral diffuse
infiltration, as well as a diffusely infiltrating growth of
relatively uniform spindled and stellated tumor cells containing
slightly enlarged nuclei, was noted. Three cases were entirely
myxoid, and in five cases more than 80% of the tumor area showed
myxoid stromal changes. In two cases each, focal fibrosarcomatous
and focal giant cell fibroblastoma-like changes were present. At
least focally, hypocellular areas were evident in one case.
Scattered enlarged tumor cells were seen in two cases. The mitotic
rate ranged from 1 to 10 mitoses in 10 high-power fields. Numerous
blood vessels with slightly fibrosed vessel walls were seen in seven
cases. Immunohistochemically, tumor cells in all cases stained
positively for CD34, and in one case each a focal expression of
alpha-smooth muscle actin and epithelial membrane antigen (EMA) was
noted. The remaining antibodies (CD99, CD31, S-100, Factor XIIIa)
were all negative. Polymerase chain reaction technique showed in one
case the characteristic COL1A1-PDGFB fusion gene. Follow-up
information in seven cases (range: 2 months to 10 years; mean: 62
months; median: 48 months) revealed a local recurrence at 5 years.
In conclusion, myxoid DFSP represents a very rare morphologic
variant with characteristic changes that has to be distinguished
from benign and malignant myxoid mesenchymal neoplasms as
superficial angiomyxoma, superficial acral fibromyxoma, myxoid
solitary fibrous tumor, myxoid perineurioma, low-grade
myxofibrosarcoma, low-grade fibromyxoid sarcoma, myxoid liposarcoma,
and myxoid synovial sarcoma. |
