Dermatofibrosarcoma protuberans, giant cell fibroblastoma, and hybrid lesions in children: clinicopathologic comparative analysis of 28 cases with molecular data--a study from the French Federation of Cancer Centers Sarcoma Group

The clinicopathologic and immunohistochemical features of 28 dermatofibrosarcoma protuberans (DFSP), giant cell fibroblastomas (GCFs), and hybrid lesions occurring in children are presented, including molecular data for seven of them. There were 19 pure adult-type DFSP (9 male and 10 female patients aged between a few days [neonate] and 13 years, median 7 years), 5 pure GCF (all males aged from 2 to 8 years, median 4 years), and 4 hybrid tumors (all males aged from 1 to 4 years, median 2.5 years). Tumor locations in pure adult-type DFSP included the trunk (6) and lower (11) and upper (2) limbs. Pure GCFs were observed on the trunk (4) and knee (1), and hybrid lesions on the trunk (2) and lower (1) and upper (1) extremities. Tumor size (n = 20) ranged from 0.6 to 5 cm (median 2 cm). Histologically, pure DFSP presented as monotonous and infiltrative, low-grade, dermal/hypodermal storiform spindle cell proliferations, sparing adnexal structures. GCF showed a dense fibrous to myxoid matrix containing slender wavy spindle cells and multinucleated giant stromal cells often lining angiectoid spaces. Hybrid lesions showed varying combinations of DFSP and GCF areas. Mitotic activity ranged from 1 to 3 mitoses per 10 high power fields. All tumors were diffusely positive for vimentin and CD34 but negative for smooth muscle actin, desmin, epithelial membrane antigen, and cytokeratins; one pure adult-type DFSP was also S-100 protein positive; <1% of nuclei were Ki67 (Mib-1) positive. One karyotyped adult-type DFSP showed an unbalanced t(17;22) (q22;q13) translocation. Multiplex RT-PCR analysis and sequencing of PCR products in seven cases showed gene fusion transcripts in two pure DFSP, two pure GCFs, and one hybrid lesion. Results were uncertain in one pure GCF; one adult-type DFSP was negative. Treatment procedures were known for 27 patients, consisting of 16 wide excisions and 11 marginal excisions. Follow-up information on 15 widely excised tumors (median 24 months; range 5-144 months) showed no recurrence. Five of six marginally excised lesions with available follow up recurred 2 months to 6 years (median 2 years) after initial surgery; all but one were cured by wide reexcision. None of the tumors metastasized. In conclusion, this study emphasizes 1) the occurrence of adult-type DFSP in children, 2) the close relationship between DFSP and GCF clinically, histologically, and molecularly, 3) the excellent prognostic of these lesions if widely excised, and 4) the diagnostic usefulness of RT-PCR analyses in detecting the gene fusion transcripts resulting from the t(17;22) (q22;q13) in paraffin-embedded tissue

Supernumerary ring chromosomes containing chromosome 17 sequences : a specific feature of dermatofibrosarcoma protuberans?

Mystery surrounds the mechanisms by which the uncommon cutaneous tumor dermatofibrosarcoma protuberans (DP) arises and progresses. A clue may be at hand in the form of extra abnormal chromosomes (one to three ring chromosomes per case with or without other chromosome abnormalities) seen in some 10 cases, including five cases in our experience. The specificity of the rings to DP would be enhanced if the rings were found to contain a contribution from a constant chromosome. We here report fluorescence in situ hybridization (FISH) results bearing on the chromosomal content of DP rings, together with clinical, pathologic, and cytogenetic documentation of our first two cases, which were briefly reported earlier, and three new DP cases. To dissect a translocation (in our 2nd case), we probed by FISH and discovered chromosome 17 sequences in the rings in all five DP cases. Nonfluorescent bands were seen on some rings painted with a whole chromosome 17 probe, indicating the presence in these rings of foreign chromosome sequences. The complexity of the rings was underscored by the detection in only one case of chromosome 17 centromeric sequences. The situation in DP seems to have parallels to that in well-differentiated liposarcoma, another tumor of intermediate malignancy with extra abnormal marker chromosome containing contributions from a constant chromosome and variable donors. In DP the supernumerary rings are clearly specific and significant

Translocation-positive Low-grade Fibromyxoid Sarcoma: Clinicopathologic and Molecular Analysis of a Series Expanding the Morphologic Spectrum and Suggesting Potential Relationship to Sclerosing Epithelioid Fibrosarcoma: A Study From the French Sarcoma Group

Low-grade fibromyxoid sarcomas (LGFMS) bear either the t(7,16) (q32-34;p11) or t(11,16) (p11;p11) translocations, resulting in FUS-CREB3L2 or FUS-CREB3L1 fusions, respectively. Heretofore, fusion transcripts were mainly detected in frozen tissues, using reverse transcription-polymerase chain reaction. In this study, we aimed to develop a reliable method to detect these in paraffin-embedded tissues, and to examine the clinicopathologic characteristics of a series of translocation-positive LGFMS. Sixty-three neoplasms with typical morphologic features of LGFMS and 66 non-LGFMS tumors selected for their resemblance to LGFMS (LGFMS-like tumors) were examined. RNA of sufficient quality could be extracted from 111/129 (86%) cases (59 LGFMS, 52 non-LGFMS). Of all, 48/59 (sensitivity, 81%) LGFMS contained detectable transcripts (45 FUS-CREB3L2, 3 FUS-CREB3L1). Most relevant clinicopathologic features of fusion-positive LGFMS included predominance in lower extremities (22/48; thigh: 13/48), deep situation (46/48), and occasional presence of unusual histologic features, for example, hypercellular areas (16/48), foci of epithelioid cells (13/48), and giant rosettes (6/48). Most tumors expressed EMA (41/45), at least focally, CD99 (38/41) and bcl-2 (36/41) while being essentially negative for CD34 (2/45), mdm2 (1/41), smooth muscle actin (1/45), S100 protein (0/46), desmin (0/44), h-caldesmon (0/42), keratins (0/44), and CD117 (0/40). Eleven presumed LGFMS were fusion negative. Of all, 7/52 non-LGMFS neoplasms contained FUS-CREB3L2 transcripts, of which 4 had been diagnosed as sclerosing epithelioid fibrosarcoma. In conclusion, FUS-CREB3L1/L2 fusion transcripts can be detected in paraffin-embedded LGFMS in a sensitive manner, using reverse transcription-polymerase chain reaction. Most fusion-positive LGFMS are EMA-positive and CD34/S100/smooth muscle actin negative. The presence of epithelioid cells and fusion transcripts in both LGFMS and a subset of sclerosing epithelioid fibrosarcoma suggest that these neoplasms might be relate