Atrophic dermatofibrosarcoma protuberans: report of a case demonstrated by detecting COL1A1-PDGFB rearrangement.

Dermatofibrosarcoma protuberans is a locally aggressive mesenchymal neoplasm. It usually presents as an indurated plaque that protrudes above the surface of the skin. Some patients have clinically persistent plaques that might be atrophic. The atrophic variant of dermatofibrosarcoma protuberans may be confused with some common skin diseases with atrophic appearance. We reported a 40-year-old woman who had a 10-year history of an atrophic dermatofibrosarcoma protuberans. Molecular analysis showed a fusion between COL1A1 exon 31 to exon 2 of PDGFB. The lesion was totally excised, with negative margins of the resection demonstrated by CD34 immunostaining. To our knowledge, this is the second case of atrophic dermatofibrosarcoma protuberans confirmed by detection of COL1A1-PDGFB fusion gene. This appears to be the first report of a fusion between COL1A1 exon 31 to exon 2 of PDGFB in atrophic dermatofibrosarcoma protuberans. VIRTUAL SLIDES: The virtual slides for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/1249657688795311.

Early recurrence in standard-risk medulloblastoma patients with the common idic(17)(p11.2) rearrangement.

Medulloblastoma is diagnosed histologically; treatment depends on staging and age of onset. Whereas clinical factors identify a standard- and a high-risk population, these findings cannot differentiate which standard-risk patients will relapse and die. Outcome is thought to be influenced by tumor subtype and molecular alterations. Poor prognosis has been associated with isochromosome (i)17q in some but not all studies. In most instances, molecular investigations document that i17q is not a true isochromosome but rather an isodicentric chromosome, idic(17)(p11.2), with rearrangement breakpoints mapping within the REPA/REPB region on 17p11.2. This study explores the clinical utility of testing for idic(17)(p11.2) rearrangements using an assay based on fluorescent in situ hybridization (FISH). This test was applied to 58 consecutive standard- and high-risk medulloblastomas with a 5-year minimum of clinical follow-up. The presence of i17q (ie, including cases not involving the common breakpoint), idic(17)(p11.2), and histologic subtype was correlated with clinical outcome. Overall survival (OS) and disease-free survival (DFS) were consistent with literature reports. Fourteen patients (25%) had i17q, with 10 (18%) involving the common isodicentric rearrangement. The presence of i17q was associated with a poor prognosis. OS and DFS were poor in all cases with anaplasia (4), unresectable disease (7), and metastases at presentation (10); however, patients with standard-risk tumors fared better. Of these 44 cases, tumors with idic(17)(p11.2) were associated with significantly worse patient outcomes and shorter mean DFS. FISH detection of idic(17)(p11.2) may be useful for risk stratification in standard-risk patients. The presence of this abnormal chromosome is associated with early recurrence of medulloblastoma.

Dermatofibrosarcoma protuberans with unusual sarcomatous transformation: a series of 4 cases with molecular confirmation.

Dermatofibrosarcoma protuberans (DFSP) is a superficial sarcoma of intermediate malignancy usually composed of monotonous short spindle cells with storiform architecture. The tumor cells are diffusely reactive for CD34 and characterized by a translocation involving chromosomes 17 and 22 or a supernumerary ring chromosome that results in the fusion of exon 2 of platelet-derived growth factor beta (PDGFß; 22q13) to various exons of collagen type 1 alpha 1 (COL1A1; 17q22). In some tumors, fibrosarcomatous transformation can occur and is characterized by a monotonous spindle cell proliferation arranged in fascicles or a herringbone-type pattern. We report 4 DFSPs with unusual and pleomorphic sarcomatous transformation. They occurred on the back, scalp, shoulder, and forehead of women (ages 31,48, 48, and 27 year). In addition to areas of conventional DFSP that strongly expressed CD34, 2 cases showed pleomorphic areas mimicking undifferentiated pleomorphic sarcoma/malignant fibrous histiocytoma: 1 case had a patternless area and 1 case had combined round/spindled cells with myxoid areas. Reverse transcription--polymerase chain reaction was performed in 1 case, confirming the presence of a COL1A1-PDGFß fusion transcript. The remaining three cases were found to be positive for a PDGFß gene rearrangement by fluorescence in situ hybridization. This series illustrates that sarcomatous transformation in DFSP may occasionally display areas, which can mimic undifferentiated pleomorphic or unclassified sarcoma. Ancillary diagnostic testing may be helpful to confirm the diagnosis, especially in small biopsies.

COL1A1:PDGFB chimeric transcripts are not present in indeterminate fibrohistiocytic lesions of the skin.

Indeterminate fibrohistiocytic lesions of the skin share histological and immunohistochemical features of both benign fibrous histiocytoma/dermatofibroma and dermatofibrosarcoma protuberans (DFSP). Unlike dermatofibroma, DFSP harbors recurrent genetic aberrations resulting in the fusion of COL1A1 on chromosome 17 and PDGFB on chromosome 22. Because indeterminate fibrohistiocytic lesions share some features with DFSP, they were evaluated for the possible presence of COL1A1-PDGFB chimeric transcripts. Twelve formalin-fixed paraffin-embedded cases were examined for COL1A1-PDGFB chimeric transcripts using a previously validated sensitive multiplex reverse transcriptase-polymerase chain reaction assay. The median patient age was 52.5 years (33-70 years) with 9 females and 3 males. The most common site was the extremities (n = 8) followed by the trunk (n = 2) and the head and neck region (n = 2). All demonstrated the expected reactivity for both CD34 and factor XIIIa, and the majority focally infiltrated into subcutaneous fat. Of the 6 patients with follow-up, 2 had residual tumor excised, but no patient developed a recurrence. None of the tumors harbored COL1A1-PDGFB fusion transcripts identified by reverse transcriptase-polymerase chain reaction. Although indeterminate fibrohistiocytic lesions share some features with DFSP, the lack of COL1A1-PDGFB chimeric transcripts suggests that they are distinct entities.

Dermatofibrosarcoma protuberans COL1A1-PDGFB fusion is identified in virtually all dermatofibrosarcoma protuberans cases when investigated by newly developed multiplex reverse transcription polymerase chain reaction and fluorescence in situ hybridization assays.

Dermatofibrosarcoma protuberans (DFSP) is a cutaneous, locally aggressive spindle cell tumor of intermediate malignancy. Tumor cells are reactive for CD34 and characterized by a t(17;22) translocation or a supernumerary ring chromosome that results in the fusion of exon 2 of PDGFB to various exons of the COL1A1 gene. We developed a multiplex reverse transcription polymerase chain reaction (RT-PCR) assay to detect fusion transcripts for all possible COL1A1 breakpoints. Twenty-seven formalin-fixed, paraffin-embedded DFSP cases were analyzed using 18 COL1A1 forward primers and 1 exon 2 PDGFB reverse primer. Sequence analysis was performed to definitively characterize breakpoints. Results were correlated with histology, immunohistochemistry, PDGFB break-apart fluorescence in situ hybridization analysis, and cytogenetics when available. Fusion transcripts were detected by RT-PCR in all but one DFSP case. Sequencing revealed a PDGFB exon 2 breakpoint in all cases. COL1A1 breakpoints were in exons 7 (1 patient), 10 (1), 29 (2), 40 (1), 46 (3), and 49 (2), and intronic between exons 13:14 (1), 26:27 (2), 30:31 (1) 33:34 (1), 43:44 (7), 45:46 (1), and 46:47 (1). Three novel COL1A1 breakpoints were identified, intronic between exons 13:14 (1), 30:31 (1) and in exon 49 (2). There was no correlation found between breakpoints and age, sex, or histologic variants. Using this sensitive multiplex RT-PCR assay in combination with fluorescence in situ hybridization, we found COL1A1-PDGFB rearrangements appear more prevalent in DFSP than previously reported. Its detection may be particularly helpful in the differential diagnosis of atypical, fibrosarcomatous, and metastatic DFSP.