Involvement of chromosomes 17 and 22 in dermatofibrosarcoma protuberans

COL1A1-PDGFB Fusion Associated Fibrosarcoma of the Uterine Corpus: A Case Report and Literature Review

Uterine collagen type 1 alpha 1 (COL1A1) and platelet-derived growth factor beta chain (PDGFB) fusion associated fibrosarcoma is a recently described entity characterized by a specific translocation t(17;22) (q22;q13) leading to the formation of COL1A1-PDGFB fusion transcripts that are typically associated with dermatofibrosarcoma protuberans. So far, only 4 cases of COL1A1-PDGFB fusion associated fibrosarcoma involving the female reproductive system have been reported in the literature. All cases showed strong diffuse expression of CD34. COL1A1-PDGFB fusion associated fibrosarcomas are aggressive tumors with a propensity for chemotherapy resistance and a poor prognosis. We are reporting the fifth case of a uterine COL1A1-PDGFB fusion associated fibrosarcoma. A 58-yr-old female presented with a large uterine mass with extension into bilateral pelvic sidewalls, mesentery of rectosigmoid colon and the vagina. A hysterectomy, bilateral salpingo-oophorectomy, and tumor debulking procedure was performed. Microscopic evaluation revealed a mitotically active cellular spindle cell neoplasm with focal osteoclast like giant cells, myxoid changes and necrosis. CD34 was diffusely and strongly positive throughout the tumor. Next-generation sequencing showed presence of the COL1A1-PDGFB fusion. The patient was treated with multiple chemotherapy regimens, however, progressed under therapy with worsening symptoms and development of extensive pelvic disease. She died of disease 13 mo after the initial diagnosis. In summary, uterine COL1A1-PDGFB fusion associated fibrosarcomas are rare tumors with aggressive clinical behavior that need to be considered in the differential diagnosis of CD34-positive uterine spindle cell neoplasms. Novel treatment options may include imatinib, a tyrosine kinase inhibitor used for treatment of advanced and unresectable dermatofibrosarcoma protuberans that was given in 1 uterine sarcoma case and showed promising initial response.

Cutaneous soft tissue tumors: how do we make sense of fibrous and "fibrohistiocytic" tumors with confusing names and similar appearances?

In the 2018 World Health Organization Classification of Skin Tumors, a wide range of predominantly benign mesenchymal neoplasms are included in the fibroblastic, myofibroblastic, and "fibrohistiocytic" categories. By far the most common of these tumors is dermatofibroma (fibrous histiocytoma). There are many histologic variants of dermatofibroma, some of which (cellular, aneurysmal, and atypical) are associated with a higher risk of local recurrence; these variants may be mistaken for more aggressive tumor types, including sarcomas. Furthermore, distinguishing among the fibrous and "fibrohistiocytic" tumors can be a diagnostic challenge, given their sometimes-similar histologic appearances and confusing nomenclature. Immunohistochemistry and molecular genetic assays play a relatively limited role in the diagnosis of these tumor types, with notable exceptions (i.e., epithelioid fibrous histiocytoma and dermatofibrosarcoma protuberans). Proper recognition of dermatofibrosarcoma protuberans is critical, since this tumor type is associated with locally aggressive behavior; transformation to the fibrosarcomatous variant brings metastatic potential. In recent years, understanding of the molecular pathogenetic basis for cutaneous mesenchymal neoplasms has increased dramatically, with the discovery of gene rearrangements in some of these tumor types. In this review, the histologic features of the most common fibrous and "fibrohistiocytic" cutaneous mesenchymal neoplasms will be discussed, as well as recently identified molecular genetic alterations.

Dermatofibrosarcoma protuberans with a novel COL6A3-PDGFD fusion gene and apparent predilection for breast

Dermatofibrosarcoma protuberans is a locally aggressive superficial mesenchymal neoplasm. It typically occurs in adulthood, and has been reported to have a slight male predilection. Tumors have a characteristic histopathologic appearance, including: storiform architecture, infiltrative "honeycomb" growth within subcutaneous adipose tissue, and immunoreactivity for CD34. Virtually all molecularly characterized cases to date have been found to harbor a COL1A1-PDGFB fusion product. Following identification of an index patient with a novel COL6A3-PDGFD fusion gene, we undertook a molecular investigation, using a combination of RNA sequencing and fluorescence in situ hybridization (FISH), to assess the prevalence of PDGFD rearrangement in dermatofibrosarcoma protuberans (N = 63). Three additional patients were found to have balanced PDGFD rearrangements. Interestingly, all 4 tumors arose on the breast of females. As a result, we subsequently examined 16 additional cases of primary breast dermatofibrosarcoma protuberans, identifying 2 additional tumors with PDGFD rearrangement. The morphology and immunophenotype of all 6 cases was analogous to those with the canonical COL1A1-PDGFB fusion; none of the cases showed fibrosarcomatous transformation. This study illustrates that the COL6A3-PDGFD fusion product is rare in dermatofibrosarcoma protuberans, and associated with an apparent predilection for breast. An awareness of this variant is important for pathologists, as it will not be detected using conventional reverse transcription polymerase chain reaction or FISH-based diagnostic assays for dermatofibrosarcoma protuberans.

Pediatric soft tissue tumor pathology: A happy morpho-molecular union

Since its foundation by remarkably talented and insightful individuals, prominently including Pepper Dehner, pediatric soft tissue tumor pathology has developed at an immense rate. The morphologic classification of tumoral entities has extensively been corroborated, but has also evolved with refinement or realignment of these classifications, through accruing molecular data, with many derivative ancillary diagnostic assays now already well-established. Tumors of unclear histogenesis, classically morphologically undifferentiated, are prominent amongst pediatric sarcomas, however, the classes of undifferentiated round- or spindle-cell-tumors-not-otherwise-specified are being dismantled gradually with the identification of their molecular underpinnings. Within recent years, for example, numerous subcategories of 'Ewing-like' round cell sarcoma have emerged. Such advances have provided the basis for novel diagnostic and prognostic sub-classifications. Efforts at defining cell- or lineage-of-origin for several tumor types have produced interesting insights especially for rhabdomyosarcoma. The remarkably early onset of pediatric sarcomas defies the theory necessitating stochastic accumulation of several somatic mutations for cancer development and indeed, these tumors may be remarkably genomically stable, often belying their aggressive nature. Much is coming to light recently regarding the role of epigenetic modifications in the evolution of these sarcomas. Indeed the morphologic features of embryonal tumors generally (not just sarcomas) may be highly reminiscent of arrested differentiation, and given the tight epigenetic regulation of cell fate determination and cell identity maintenance, a theory of epigenetically-driven oncogenesis sits easily with these tumors. The age-delimited distinct biologies of 'pediatric' and adult GIST are intriguing, particularly, the SDH-deficient 'pediatric' form, driven by a metabolic defect, but resulting in epigenetic dysregulation with genome-wide DNA methylation changes. There is little doubt that many of the gaps in our understanding of pediatric sarcoma biology will be filled by a deeper appreciation of the role of dysregulated epigenetics including chromatin biology, perhaps best exemplified in malignant rhabdoid tumor. The field of pediatric soft tissue tumor pathology grows ever more interesting. Importantly though, it must be emphasized, that none of this progress could have occurred, or indeed continue, without the initial step of accurate diagnosis, founded solidly on morphology - thank you Pepper for your unparalleled contributions to this field! The opportunity to be your apprentice for five years has been a bigger and more positive influence than words can express.

Fluorescence in situ hybridization analysis is a helpful test for the diagnosis of dermatofibrosarcoma protuberans

Cytogenetically, most dermatofibrosarcoma protuberans are characterized by chromosomal rearrangements resulting in the collagen type-1 alpha 1 (COL1A1)-platelet-derived growth factor β (PDGFB) fusion gene. This abnormality can be detected by fluorescence in situ hybridization (FISH) analysis in routine practice. The aim of this study was to evaluate the role of the FISH analysis in the diagnosis of dermatofibrosarcoma protuberans. A FISH analysis was prospectively and systematically performed on a series of 448 consecutive tumor specimens. All cases were reviewed by two independent pathologists and classified in three categories according to the probability of a DFSP diagnosis before molecular analyses. Cases were classified as certain when dermatofibrosarcoma protuberans was the only possible diagnosis. Those cases for which dermatofibrosarcoma protuberans remained the first diagnosis, but other differential diagnosis existed, were regarded as probable. When dermatofibrosarcoma protuberans was considered a differential diagnosis, they were labeled as possible. The final diagnosis was supported by clinicopathological findings and results of FISH analyses. Immunohistochemical analysis of CD34 was systematically performed, and additional markers when necessary. The cases (n=37) with a non-interpretable FISH were excluded. For the 185 certain tumors specimens: 178 (96%) FISH analyses showed a PDGFB/COL1A1 rearrangement, 7 (4%) were negative. For the 114 probable tumors specimens: 104 (91%) FISH analyses were positive and 10 (9%) were negative leading to a new diagnosis in 8 cases. For the 112 possible cases: 91 (81%) FISH analyses were negative and 21 (19%) were positive. Of the 21 cases, initial diagnoses included unclassified sarcoma, myxofibrosarcoma, dermatofibroma, reactive lesion, solitary fibrous tumor, perineurioma, benign nerve sheath tumor, and undifferentiated spindle cell tumor without malignant evidence. FISH analysis has been helpful for confirming the diagnosis of dermatofibrosarcoma protuberans in 25% (104/411) of cases and necessary for the diagnosis of dermatofibrosarcoma protuberans in 5% (21/411) of cases.

Molecular diagnostics complementing morphology in superficial mesenchymal tumors

Molecular techniques are increasingly important in the practice of surgical pathology. In soft tissue tumors, there are a number of tumors with recurring cytogenetic abnormalities. Knowledge of these abnormalities has furthered our understanding of these tumors and has also allowed development of molecular techniques to aid in the diagnosis. This review will focus on mesenchymal tumors with specific cytogenetic abnormalities that may present as a superficial tumor of the dermis or subcutis.

Dermatofibrosarcoma protuberans in children: an update on the diagnosis and treatment

Dermatofibrosarcoma protuberans (DFSP) is a fibrohistiocytic tumor of low grade malignant potential. Although rare, pediatric cases pose a particular challenge in diagnosis and management. In children, the clinical appearance may be heterogeneous and a high index of suspicion is necessary to avoid delays in diagnosis which can lead to further morbidity. Histologic examination, often with the use of appropriate immunostains, is necessary for diagnosis. Advances in the understanding of the molecular genetics of DFSP have led to further diagnostic and therapeutic modalities. DFSP is thought to result from a translocation between platelet-derived growth factor beta (PDGFB, 22q13.1) and type 1 collagen (COL1A1, 17q21≈22) leading to a fusion protein (PDGFB) which stimulates the PDGF receptor. Detection of this translocation in tissue via PCR or fluorescence in situ hybridization (FISH) can be helpful in difficult cases. While surgery with wide local excision or Mohs micrographic surgery is the mainstay of treatment, the use of targeted therapy with imatanib mesylate shows promise in large or unresectable tumors. Knowledge of the clinical features, histology, genetics, and treatment options is important for successful management of these tumors.

Fibrous and fibrohistiocytic neoplasms: an update

Important advances in fibroblastic and fibrohistiocytic tumors relevant to dermatologists and dermatopathologists include (1) recognition that myxofibrosarcoma is a distinct entity that frequently arises in skin; (2) CD10 is sensitive but not specific atypical fibroxanthoma; (3) neurothekeomas lacking S100 expression are probably fibrohistiocytic/fibroblastic tumors, whereas S100+ myxoid variants are better classified as nerve sheath myxomas; (4) the recognition of a primary cutaneous variant of solitary fibrous tumor; (5) thelimitations of b-catenin immunohistochemistry in desmoid tumors; and (6) the prognostic utility of clinical and histopathologic variables in dermatofibrosarcoma protuberans, and the effects of imatinib mesylate therapy.

Response of malignant scalp dermatofibrosarcoma to presurgical targeted growth factor inhibition

Dermatofibrosarcoma protuberans (DFSP) is an uncommon, locally aggressive, malignant cutaneous tumor that sparingly presents on the scalp. Dermatofibrosarcomas often result from the formation of a fusion oncogene on translocated or supernumerary ring chromosomes 17 and 22, causing the overexpression of PDGFRβ driven by the COL1A1 promoter. Because of uncertainty surrounding appropriate treatment of aggressive scalp DFSP, the authors performed an extensive review of the available data from a MEDLINE (Ovid) search to describe the clinical presentation and treatment options for this rare tumor. Their search identified 39 different cases, including the illustrative case presented in this study.

Adjuvant therapy for this malignant lesion is not universally established in the literature. In the present case, the authors successfully treated a locally invasive scalp DFSP with presurgical therapy that specifically inhibited the PDGFβ receptor. Imatinib significantly shrank the DFSP tumor mass, reduced hypervascularity, reduced metabolic activity on PET scanning, and permitted a safe gross-total resection. Although wide excision and Mohs micrographic surgery remain the standard surgical treatments for DFSP, the authors illustrate that presurgical chemotherapeutic treatment by imatinib provides a critical adjunct to traditional therapy.

Classification and pathology

Soft tissue tumors are a heterogeneous group of benign and malignant processes. Some are assumed to be reactive; others are clearly neoplastic. Because of their rarity, they frequently pose diagnostic problems for surgical pathologists. Accurate diagnosis of these tumors is enhanced by knowledge of the clinical features of the given lesions and, at times, by application of immunohistochemical and molecular techniques. In this article the lesions are described essentially in accordance with the World Health Organization classification.

Giant cell fibroblastoma: an update and addition of 86 new cases from the Armed Forces Institute of Pathology, in honor of Dr. Franz M. Enzinger

A quarter of a century ago at the International Academy of Pathology in Boston, Mass, Drs Enzinger and Shmookler's seminal abstract on giant cell fibroblastoma (GCF) included 20 GCFs on the back and thigh of mostly male children. These tumors involved dermis and subcutis, and had parallel fascicles of wavy uniform spindled cells with wiry collagen, dense sclerosis, and gaping spaces with scattered and rimming pleomorphic giant cells. EM suggested fibroblastic phenotype. All cases had benign behavior, but almost half recurred. The caveat was mistaking this tumor for a malignancy. In 1989, Drs Enzinger, Shmookler, and Weiss published this abstract as 28 cases from the AFIP (1960-1981), including 4 adults up to 55 years old. They proposed a relationship of this childhood tumor to dermatofibrosarcoma protuberans (DFSP). Since these original descriptions of GCF, there has been additional immunohistochemical and molecular support for a relationship between DFSP and GCF. We reviewed additional AFIP cases of GCF since 1981, in honor of Dr Enzinger. These new cases included 60 males and 26 females, whose ages ranged from 6 months to 62 years (median, 6 years; 62%, younger than 10 years; 77%, younger than 20 years; and only 10 patients were older than 40 years). Thirty-nine GCF cases with evaluable epidermis were observed to be protuberant, one with superficial ulceration. Most cases were dermal and subcutaneous, 3 purely dermal, and 5 involved superficial skeletal muscle. Almost all cases demonstrated a honeycomb pattern, and several, a parallel pattern of infiltration. Several cases spared adnexa. Pure GCF areas ranged from solid and collagenized to angiectoid and myxoid, the latter with small to large cystlike spaces. Most cases were relatively hypocellular, except one case with more atypia and mitotic activity. GCF demonstrated myoid whorls in 2 cases, a feature previously described in DFSP. Most remarkable is the peculiar perivascular lymphocytes in an onionskin pattern in GCF, not observed in DFSP. Furthermore, histologic intralesional hemorrhage seems to be common in GCF, particularly near the fascia. Fourteen of our 86 cases demonstrated 5% to 70% (median, 20%) dense nongiant cell storiform areas, interpreted as hybrid GCF-DFSP. Three of these cases demonstrated hypercellular DFSP. One hybrid case had fibrosarcomatous transformation. Two cases of pure GCF recurred as a hybrid tumor with DFSP areas, one of these with hypercellular DFSP. In all but one case, the DFSP was adjacent to GCF with an abrupt transition. Most cases studied were positive for CD34 (more intense in DFSP than relatively hypocellular GCF areas) and negative for smooth muscle actin, desmin, HMB-45, keratin, and S100 protein. GCF is exactly clinically and morphologically the same as Dr Enzinger and colleagues originally described it. Additional observations of marked perivascular and onionskin-like chronic inflammation and consistent hemorrhage may aid in the diagnosis of this previously well-described tumor. Collectively, we now have even more convincing morphologic, immunophenotypic, and molecular evidence that GCF is on a spectrum with DFSP.

Dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a soft tissue neoplasm of intermediate malignancy that is initially localized to the skin from where it can invade deep structures (fat, fascia, muscle and bone). It is the most frequent fibrohistiocytic tumor, comprising approximately 1.8 % of all soft tissue sarcomas and 0.1 % of all cancers. It has an estimated incidence of 0.8-5 cases per one million persons per year. Treatment of localized disease consists in complete surgical excision of the lesion by conventional surgery with wide margins (>3 cm) or by micrographic Mohs surgery. Although the cases of metastatic DFSP do not reach 5 % of the total, almost all of them appear after previous local relapses. The prognosis for metastatic cases is very poor with a survival of less than 2 years following detection of metastatic disease. Patients with locally advanced DFSP are not candidates for an initial radical surgical therapy therefore neoadyuvant treatment is required prior to surgery in order to reduce tumor burden. In this regard, chemotherapy and radiotherapy have not been highly efficacious so it is necessary to consider new alternatives. The demonstration of the oncogenic power of the translocation COL1A1-PDGFB in DFSP has allowed the successful introduction of drug therapy with antagonists of the PDGFB receptor for metastatic or locally advanced cases.

Análisis del gen de fusión COL1A1-PDGFB en un caso de dermatofibrosarcoma protuberans con componente de fibrosarcoma

Dermatofibrosarcoma protuberans (DFSP) is an infrequent tumor of intermediate malignancy, with little tendency to develop metastases but with a high rate of local recurrence. Cytogenetically, DFSP is characterized by a reciprocal translocation, t(17;22)(q22;q13), which is a conditioning factor in the fusion of the collagen type I alpha I gene (COL1A1) in chromosome 17q with the platelet-derived growth factor beta chain gene (PDGFB) in chromosome 22q. The fusion of these genes is variable, involving one of the 51 exons of the COL1A1 gene and exon 2 of the PDGFB gene. We present the case of a 37-year-old woman with a tumor on the arm whose histology showed a neoplastic infiltration of the subcutaneous cellular tissue made up of fusiform cells with an elongated nucleus in a storiform pattern and other more pleomorphic cells in a herringbone pattern, compatible with DFSP with a fibrosarcoma component. The molecular biology study with RT-PCR analysis of paraffin-embedded material and later sequencing showed a new fusion of exon 19 of the COL1A1 gene and exon 2 of PDGFB, supporting a diagnosis of DFSP. A study of the COL1A1-PDGFB fusion products is useful in cases where histology and immunohistochemistry are insufficient for the differential diagnosis of DFSP versus other sarcomas. It also justifies the use of new avenues of treatment with tyrosine kinase inhibitors.

Dermatofibrosarcoma protuberans: report of a case with a variant ring chromosome and metastases following pregnancy

BACKGROUND

The most frequent molecular abnormality observed in dermatofibrosarcoma protuberans (DFSP) is the formation of a supernumerary ring chromosome or translocation resulting in fusion of the gene encoding the alpha-chain of type 1 collagen, COL1A1 from 17q22, to the platelet-derived growth factor beta-chain, PDGFB gene from 22q13. Rare cases documenting variant ring or marker chromosomes involving regions other than 17q22 and 22q13 have been reported. Further analysis in three of these cases demonstrated the presence of the COL1A1 and PDGFB genes.

METHODS

We report a further case of DFSP with a rare variant ring chromosome. The tumor appeared to undergo accelerated growth during pregnancy, then metastasized following pregnancy. We describe the clinical, histological, immunohistochemical, and cytogenetic features.

RESULTS

The metastatic tumor showed a variant r(17;?) chromosome. A locus-specific probe was required to demonstrate presence of the PDGFB gene within the ring, indicating cryptic molecular rearrangement between chromosomes 17 and 22, and recombination with an unknown chromosome.

CONCLUSIONS

Cryptic rearrangement of chromosomes 17 and 22 should be suspected in variant ring chromosomes and translocations. Pregnancy may contribute to accelerated growth of DFSP, and delay in surgical resection should be avoided.

Congenital dermatofibrosarcoma protuberans with fibrosarcomatous and myxoid change

This report describes a case of congenital dermatofibrosarcoma protuberans (DFSP) with fibrosarcomatous (FS) and myxoid areas. Immunohistochemical results showed that tumour cells in ordinary DFSP areas were diffusely positive for CD34, whereas in the FS and myxoid areas, few tumour cells were positive for this antigen. Ki-67 positive tumour cell numbers were greater in the FS (11.8%) and myxoid areas (19.8%) relative to ordinary DFSP areas (2.2%). Reverse transcription polymerase chain reaction and sequence analysis showed the presence of an identical COL1A1-PDGFB fusion transcript in ordinary DFSP (plaque-like area), FS, and myxoid areas of DFSP. These results indicate that the three components of DFSP have a common histogenesis. This study documents the first application of gene analysis involving the myxoid area of DFSP.

Genetics of dermatofibrosarcoma protuberans family of tumors: from ring chromosomes to tyrosine kinase inhibitor treatment

Dermatofibrosarcoma protuberans (DP) is a rare, slow-growing, infiltrating dermal neoplasm of intermediate malignancy, made up of spindle-shaped tumor cells often positive for CD34. The preferred treatment is wide surgical excision with pathologically negative margins. At the cytogenetic level, DP cells are characterized by either supernumerary ring chromosomes, which have been shown by using fluorescence in situ hybridization techniques to be derived from chromosome 22 and to contain low-level amplified sequences from 17q22-qter and 22q10-q13.1, or t(17;22), that are most often unbalanced. Both the rings and linear der(22) contain a specific fusion of COL1A1 with PDGFB. Similar to other tumors, the COL1A1-PDGFB fusion is occasionally cryptic, associated with complex chromosomal rearrangements. Although rings have been mainly observed in adults, translocations have been reported in all pediatric cases. DP is therefore a unique example of a tumor in which (i) the same molecular event occurs either on rings or linear translocation derivatives, (ii) the chromosomal abnormalities display an age-related pattern, and (iii) the presence of the specific fusion gene is associated with the gain of chromosomal segments, probably taking advantage of gene dosage effects. In all DP cases that underwent molecular investigations, the breakpoint localization in PDGFB was found to be remarkably constant, placing exon 2 under the control of the COL1A1 promoter. In contrast, the COL1A1 breakpoint was found to be variably located within the exons of the alpha-helical coding region (exons 6-49). No preferential COL1A1 breakpoint and no correlation between the breakpoint location and the age of the patient or any clinical or histological particularity have been described. The COL1A1-PDGFB fusion is detectable by multiplex RT-PCR with a combination of forward primers designed from a variety of COL1A1 exons and one reverse primer from PDGFB exon 2. Recent studies have determined the molecular identity of "classical" DP, giant cell fibroblastoma, Bednar tumor, adult superficial fibrosarcoma, and the granular cell variant of DP. In approximately 8% of DP cases, the COL1A1-PDGFB fusion is not found, suggesting that genes other than COL1A1 or PDGFB might be involved in a subset of cases. It has been proposed that PDGFB acts as a mitogen in DP cells by autocrine stimulation of the PDGF receptor. It is encouraging that inhibitory effects of the PDGF receptor tyrosine kinase antagonist imatinib mesylate have been demonstrated in vivo; such targeted therapies might be warranted in the near future for treatment of the few DP cases not manageable by surgery.

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 tissues.

COL1A1-PDGFB gene fusion demonstrates a common histogenetic origin for dermatofibrosarcoma protuberans and its granular cell variant

Granular cell variant of dermatofibrosarcoma protuberans is very rare with only one report of two cases. We report a new case in which we demonstrated the presence of the dermatofibrosarcoma protuberans-specific COL1A1-PDGFB fusion from paraffin-embedded tissue. This case analysis demonstrated the utility of molecular genetics as a powerful tool for the diagnosis of atypical forms of dermatofibrosarcoma protuberans.

Fusion of COL1A1 exon 29 with PDGFB exon 2 in a der(22)t(17;22) in a pediatric giant cell fibroblastoma with a pigmented Bednar tumor component. Evidence for age-related chromosomal pattern in dermatofibrosarcoma protuberans and related tumors

In contrast with classic dermatofibrosarcoma protuberans (DP), genetic information about the juvenile or pigmented variant forms of DP, so-called giant cell fibroblastoma (GCF) and Bednar tumor (BT), is limited. In the sole karyotyped case of BT a supernumerary ring containing chromosomes 17 and 22 sequences, similar to DP rings, was reported, whereas in three GCF cases, t(17;22) or der(22)t(17;22) with COL1A1-PDGFB fusion involving exons 11, 40, and 47, respectively, have been described. Here, we report the first cytogenetic and molecular analysis of a tumor from a 5-year-old child that contained both GCF and BT components. The karyotype and molecular analyses confirmed the common histogenetic origin between DP, GCF, and BT in showing the presence of a der(22)t(17;22) fusing the COL1A1 exon 29 to PDGFB exon 2. Because COL1A1 exon 29 has been involved previously in gene fusion with PDGFB exon 2 in several cases of adult or infantile DP presenting either t(17;22) or ring chromosomes, our results support the concept that DP, GCF, and BT are morphologic variants of a same entity, rather than distinct tumors. Of interest, our findings give prominence to the relation between patient age and the chromosomal rearrangement pattern in DP and related tumors. Whereas only a few adult DP cases presented with translocations, all the infantile cases, either DP, GCF, or mixed BT-GCF, as shown here, contained translocation derivatives but not ring chromosomes. All the ring chromosomes were observed in adult cases. With respect to cytogenetic studies, DP, GCF, and BT appear to be a unique model for age-related chromosomal rearrangement progression.

Overrepresentation of 17q22-qter and 22q13 in dermatofibrosarcoma protuberans but not in dermatofibroma: a comparative genomic hybridization study

Histopathological differentiation between dermatofibrosarcoma protuberans (DFSP) and dermatofibroma (DF) is often difficult, because both neoplasms share some clinical features and the presence of a storiform pattern. In the present study, we investigated the usefulness of comparative genomic hybridization (CGH) in the diagnosis of these entities by examining 12 DFSP and 12 DF cases. The most frequent DNA sequence copy number changes detected in 10 (83%) of 12 DFSP cases (mean, 1.9 aberrations/tumor; range, 0-3) consisted of gains of 17q22-qter (10 tumors), 22q13 (nine tumors), and 8q24.1-qter (three tumors). High-level amplification, which was detected in three tumors, was seen only in chromosome 17, with 17q23-q25 as the minimal common region. Loss of DNA sequences was not found in DFSP cases. In contrast, two (17%) of the 12 DF cases (mean, 0.5 aberrations/tumor; range, 0-4) showed DNA sequence copy number changes, although recurrent gains and losses and high-level amplifications were not observed. Gains were more common than losses in DF. Overrepresentation of 17q and 22q sequences was a common finding in DFSP but not in DF. Thus, CGH seems to be useful for distinguishing DFSP from DF in most cases.

Supernumerary ring chromosomes in dermatofibrosarcoma protuberans may contain sequences from 8q11.2-qter and 17q21-qter: a combined cytogenetic and comparative genomic hybridization study

Dermatofibrosarcoma protuberans (DFSP) presents with characteristic cytogenetic features such as reciprocal t(17;22)(q22;q13) or, more commonly, supernumerary ring chromosomes containing sequences from chromosomes 17 and 22. Here, we report the identification of a novel abnormality in a 43-year-old woman with DFSP. Cytogenetic analysis of tumor cells showed the presence of a supernumerary ring chromosome as the sole anomaly. Amplification of 8q11.2 approximately qter and 17q21 approximately qter sequences was confirmed by comparative genomic hybridization (CGH); the present case apparently lacked amplification of chromosome 22. To our knowledge, this is the first case indicating that the ring chromosome in DFSP is possibly associated with amplified material from chromosomes 8 and 17.

Spectral karyotyping reveals 17;22 fusions in a cytogenetically atypical dermatofibrosarcoma protuberans with a large marker chromosome as a sole abnormality

The presence of an extra ring chromosome containing material from 17q and 22q, or, less frequently, a t(17;22)(q22;q13), is a cytogenetic hallmark of dermatofibrosarcoma protuberans (DFSP). However, occasionally tumors with other, atypical karyotypes are encountered. We describe a case of recurrent DFSP without a ring chromosome or a t(17;22) on standard cytogenetic analysis. In all cells analyzed by G-banding, an additional, large marker chromosome was present as a sole abnormality. This chromosome apparently included chromosome 8 or the 8q arm, but the origin of its remaining part could not be determined with certainty. To characterize further the abnormal chromosome, we applied spectral karyotyping (SKY). SKY confirmed the presence of an extra chromosome 8 or arm 8q in the marker and showed that its remaining part was composed of segments from chromosomes 7, 17, 21, and 22, with two copies of a 17;22 fusion. Our results and the literature data suggest that, in addition to a specific 17;22 fusion, amplification of material from chromosomes 17, 22, 8, 5, 7, and 21 may play a role in DFSP development and/or progression. Furthermore, our case demonstrates the usefulness of SKY in detection of a diagnostically relevant 17;22 fusion in DFSP patients who have unusual karyotypic features.

CD34-positive cellular blue nevi

BACKGROUND

Although cellular blue nevi (CBN) are well known and characterized, the histopathologic and clinical spectrum of these tumors continues to evolve. We report four CBN with a distinctive histologic and immunohistochemical pattern.

METHODS

The histologic features and immunohistochemical staining for S-100 protein, HMB-45, Bcl-2 and CD34 of four CBN with distinctive features were evaluated using routine methods and compared to common CBN.

RESULTS

All four of these distinctive CBN where known to be congenital, and all showed aggregates of plump spindled cells with round to oval nuclei in aggregates and more slender spindled cells with thin wavy nuclei. The slender, spindled cells showed an infiltrative pattern laterally into the dermis and deep into the subcutaneous fat. All four tumors showed diffuse expression of an immunohistochemical stain for CD34, as well as for S-100 protein, Bcl-2, and HMB-45.

CONCLUSION

Positive immunohistochemical staining with the progenitor marker CD34 defines a subset of CBN. These tumors appear to fit within the spectrum of neurocristic cutaneous hamartomas and may arise from more primitive neurocristically derived cells. Further follow-up of these tumors will be necessary to determine whether this subset of CBN defines a subset with a characteristic biologic behavior.

Low grade fibromyxoid sarcoma. a further low-grade soft tissue malignancy characterized by a ring chromosome

Supernumerary rings in the context of a simple karyotype characterize several low-grade malignant tumors of soft tissue and bone. Low-grade fibromyxoid sarcoma is an uncommon low-grade sarcoma, the cytogenetics of which has not yet been reported. Here we describe the first molecular-cytogenetic characterization of a pulmonary metastasis of low-grade fibromyxoid sarcoma. The histology of the primary and recurrent tumors was consistent with the diagnosis of low-grade fibromyxoid sarcoma of the usual type, whereas the pulmonary metastasis was of the "giant rosettes" variant. Cytogenetic analysis revealed a ring chromosome. Because gain of material of chromosomes 7 and 16 was detected by CGH, the ring chromosome is assumed to be composed of material from these respective chromosomes.

A giant cell angiofibroma involving 6q

Giant cell angiofibroma, a recently proposed new clinicopathological entity, arises exclusively in the orbit in adults and histologically exhibits features intermediate between those of giant cell fibroblastoma and solitary fibrous tumor. In a typical case of giant cell angiofibroma, abnormalities of chromosome 6 with a common pattern involving 6q13 were detected together with various other chromosomal aberrations. To our knowledge, this is the first reported case of giant cell angiofibroma demonstrating chromosomal abnormalities.

Accelerated growth of dermatofibrosarcoma protuberans during pregnancy

Dermatofibrosarcoma protuberans (DFSPs) are uncommon skin tumors that have a high incidence of local recurrence even with wide surgical margin, but DFSPs rarely metastasize. Previous reports have suggested that DFSPs may enlarge more rapidly during pregnancy. We report 3 additional cases of DFSPs that showed accelerated growth during pregnancy. Immunohistochemical stains for CD34, S-100 protein, factor XIIIa, and estrogen and progesterone receptors were performed on biopsy specimens. The tumors in all 3 patients, and 4 additional DFSPs from 2 male and 2 female subjects, showed expression of progesterone receptor. As with many other stromal neoplasms, DFSPs appear to express low levels of hormone receptors, which may be one factor that accounts for their accelerated growth during pregnancy.

A case of dermatofibrosarcoma protuberans with a ring chromosome 5 and a rearranged chromosome 22 containing amplified COL1A1 and PDGFB sequences

Dermatofibrosarcoma protuberans (DFSP) is a cutaneous tumour of borderline malignancy, the cytogenetic features of which include the translocation t(17;22)(q22;q13) or, more commonly, supernumerary ring chromosomes containing material from 17q22 and 22q13. These rearrangements result in the COL1A1/PDGFB fusion gene. Here, we describe a case of DFSP displaying a ring chromosome 5 together with a large marker chromosome composed of chromosome 22 alphoid DNA, material from distal 12q and amplified COL1A1 and PDGFB sequences. This is the first case of DFSP with multiple copies of COL1A1 and PDGFB not confined to ring chromosomes, showing that DFSP is similar to other borderline malignant mesenchymal tumours, where rings and giant markers are alternative vehicles for amplified material.

Pretreatment with intralesional hyaluronidase prior to excision of dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSPs) are an uncommon malignancy that commonly recur, but rarely metastasize. The origin of DFSPs is controversial; however, they stain with the progenitor marker CD34. DFSPs usually show increased stromal mucin, mainly hyaluronic acid (HA). HA increases cellular proliferation, delays differentiation and increases cellular motion. We evaluated the pretreatment of DFSPs with intralesional injections of hyaluronidase (HD) prior to the surgical excision. Five of nine cases of DFSPs were pretreated with HD. In HD-pretreated cases the margins for excision of the residual tumor were reduced. HD pretreatment also decreased CD34 staining and increased polarizable collagen in the residual tumor.

Cutaneous fibrous perineurioma

Tumors of perineurial origin are rare. Three variants of perineuriomas have been described, a storiform perineurial fibroma, an intraneural perineurioma, and a recently described sclerosing perineurioma. We present two patients with cutaneous fibrous perineurioma located in acral areas. Both tumors had a deep circumscribed margin with a prominent vascular component. They contained small round cells and spindle cells that express EMA and show membrane staining for type IV collagen. Cutaneous fibrous perineuriomas fit within the spectrum of neurocristicly derived cellular proliferations.

Relevance of cytogenetic and fluorescent in situ hybridization analyses in the clinical assessment of soft tissue sarcoma

Soft tissue sarcomas are a heterogeneous group of malignant tumors displaying a wide range of clinical presentations, morphological features, and biological behaviors. These characteristics and the recent development of differentiated treatment regimens for the different types of soft tissue sarcomas call for refined histological classification using additional ancillary approaches such as cytogenetic and molecular genetic analyses. We coupled classical cytogenetics and fluorescent in situ hybridization (FISH) on both metaphases and interphase nuclei to show the feasibility of this approach to characterize tumor type-specific chromosome rearrangements in soft tissue sarcomas of different histotype. In 35 cases analyzed, we detected the presence of specific chromosome rearrangements such as t(X;18) in synovial sarcoma (SS), t(12;16) in myxoid liposarcoma (MLS), t(11;22) in peripheral primitive neuroectodermal tumors (pPNET), t(2;13) in alveolar rhabdomyosarcoma (ARMS) and ring chromosomes in dermatofibrosarcoma protuberans (DFSP). In several cases, the presence of these cytogenetic rearrangements was of help for a differential diagnosis. The FISH analysis using painting probes not only confirmed the cytogenetic results but also allowed the identification of tumor-specific chromosome changes in those cases presenting low mitotic index or with poor quality chromosomes. Moreover, in the absence of analysable metaphases, FISH was successfully performed on interphase nuclei. Taken together, these results indicate both the diagnostic and clinical relevance of a molecular cytogenetic analysis in the study of soft tissue sarcomas.

Deregulation of the platelet-derived growth factor B-chain gene via fusion with collagen gene COL1A1 in dermatofibrosarcoma protuberans and giant-cell fibroblastoma

Dermatofibrosarcoma protuberans (DP), an infiltrative skin tumour of intermediate malignancy, presents specific features such as reciprocal translocations t(17;22)(q22;q13) and supernumerary ring chromosomes derived from the t(17;22). In this report, the breakpoints from translocations and rings in DP and its juvenile form, giant cell fibroblastoma (GCF), were characterised on the genomic and RNA level. These rearrangements fuse the platelet-derived growth factor B-chain (PDGFB, c-sis proto-oncogene) and the collagen type I alpha 1 (COL1A1) genes. PDGFB has transforming activity and is a potent mitogen for a number of cell types, but its role in oncogenic processes is not fully understood. COL1A1 is a major constituent of the connective tissue matrix. Neither PDGFB nor COL1A1 have so far been implicated in any tumour translocations. These gene fusions delete exon 1 of PDGFB, and release this growth factor from its normal regulation.

Another case of t(17;22)(q22;q13) in an infantile dermatofibrosarcoma protuberans

We have identified a new dermatofibrosarcoma protuberans (DP) case with a t(17;22) (q22;q13) occurring in a child. The translocation was substantiated by the presence of one or two copies of the sole der(22)t(17;22). This rearrangement added to two normal chromosomes 17 and one or two chromosomes 22, resulted in trisomy 22cen-q13 and trisomy (or tetrasomy) 17q22-25. This observation confirms the specificity of the association of DP with the t(17;22) found together with extra copies of the der(22)t(17;22). It also points out a possible prevalence of translocation rather than rings in DP of the childhood disease.