LAUSR

107 (figure 1J) and a herringbone pattern in the other half (figure 1K). CD34 was diffusely positive in both areas with storiform (figure 1I) and herringbone pattern (figure 1M). The MIB-1 index was approximately 10%, and p53 was negative over the entire lesion. No local recurrence or metastasis was detected two years after excision. Cases of DFSP in patients aged 18 or younger accounts for approximately 6% of all DFSP cases [1], and the disease is more likely to affect the lower extremities in these patients than adult patients [2]. Paediatric cases are less likely to suffer from local recurrence or metastasis (the local recurrence rate is reported to be 13.7% and <0.13%, and metastasis rate 1.1% and <0.03% in all cases and patients aged 18 or younger, respectively [3]). This could be attributable to the fact that advanced age and upper extremity involvement are risk factors for recurrence [4]. FS-DFSP is characterized by the structure of the fascicular or herringbone pattern, hypercellularity, abundant atypical cells, increased mitotic rate, decreased CD34 positivity (approximately 45% of FS-DFSP cases are CD34 negative) [5], and the presence of fibrosarcomatous change in at least 5% of the lesion [6]. FS-DFSP accounts for 10-20% of all DFSP [5]. Both the local recurrence rate and metastasis rate of FS-DFSP are higher than that for DFSP alone [5]. To the best of our knowledge, only 11 FS-DFSP patients aged 18 or younger, including our case, have been reported [7, 8]. We estimated that FS-DFSP cases are seen in less than 6% (11/184) of all DFSP cases of young age, with the assumption that the total number of paediatric DFSP cases is more than 183, based on a report in which 183 cases of histologically confirmed DFSP were described in young age [2]. The mean age was 10.5 years (range: 2-18 years), with a female to male ratio of 1:1 (five females and five males; one not specified). The lesion appeared most frequently on the thigh (4/11). Two out of eight cases with available data had decreased CD34 positivity in areas with fibrosarcomatous change. Local recurrence occurred in two patients and distant metastasis was reported in two patients, one of whom also developed local recurrence. To achieve clear margins, wide local excision is the first-line treatment. Radiotherapy is not recommended in paediatric cases, unlike adult cases. For unresectable or metastatic DFSP, imatinib mesylate, a PDGFR inhibitor, is the treatment of choice [8]. Much attention should be paid to the disease course of FS-DFSP due to the paucity of previously reported cases.