[73] Prognostic Features of Myxofibrosarcoma: A Clinicopathologic Study Assessing the Impact of FNCLCC Grading System

Wonwoo Shon, Michael M Wolz, Sarah M Jenksins, Karen J Fritchie. Mayo Clinic, Rochester, MN

Background: There has been variability in the diagnostic and grading criteria of myxofibrosarcoma. To address these issues we undertook a retrospective review of myxofibrosarcomas to assess the prognostic effectiveness of the widely accepted FNCLLC grading system and to determine what clinicopathologic features are important in prognosis.
Design: The Mayo Clinic pathology archive was searched for primary, non-treated cases of myxofibrosarcoma. 32 cases of myxofibrosarcoma meeting these criteria were evaluated with regards to size, atypia (mild, moderate, severe), % myxoid area (<5%, 5-50%, >50%), mitotic rate (per 10 high power fields), and % tumor necrosis (0, ≤50%, >50%). All cases were also graded using the FNCLCC grading system.
Results: Table 1 summaries the histopathologic features of 32 studied cases. The tumors occurred in 19 females and 13 males, ranging from 27.8 to 87.7 years (median 69.4 years). The lesions ranged in size from 1.5 to 16.5 cm (mean 6.2 cm) and involved the lower (19) and upper (7) extremities, trunk (2), head (2), shoulder (1), and buttock (1). FNCLCC grades were: Grade 1 (12), Grade 2 (14), and Grade 3 (6). Follow-up information was available for 31 patients (range 0.1 to 17.9 years; mean 4.2 years; median 3.0 years). The 5-year overall survival and recurrence/metastasis-free rates were 70.9 % and 59.6%, respectively. By Cox univariate analysis, tumor size greater than 5 cm (p=0.0004) and presence of tumor necrosis (p=0.0262) correlated with increased mortality. Other morphologic parameters, including FNCLCC grade (p=0.14), degree of atypia (p=0.82), mitotic count (p=0.47) and myxoid component (p=0.84), showed no significant association with outcome.
Conclusions: The tumor size (>5 cm) and presence of tumor necrosis were identified as statistically significant factors for poor outcome. This data also suggests that the current FNCLCC grading system may not be useful as a prognostic indicator for myxofibrosarcoma. The percentage of myxoid area did not correlate with outcome, suggesting that tumors with any myxoid component (even <5%) be considered in the spectrum of myxofibrosarcoma.

Histopathologic findings of 32 myxofibrosarcomas
 Total (N=32)
% Myxoid 
<5%7 (21.9%)
5-50%8 (25%)
>50%17 (53.1%)
Cytologic atypia 
Mild1 (3.1%)
Moderate12 (37.5%)
Severe19 (59.4%)
Mitotic rate 
<10HPF19 (59.4%)
10-20HPF5 (15.6%)
>20HPF8 (25%)
% tumor necrosis 
018 (56.3%)
≤50%11 (34.4%)
>50%3 (9.4%)
112 (37.5%)
214 (43.8%)
36 (18.8%)

Category: Bone & Soft Tissue

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 9, Monday Morning


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