Superficial Angiomyxomas Frequently Demonstrate Loss of Protein Kinase A Regulatory Subunit 1 Alpha Expression: Immunohistochemical Analysis of 29 Cases and Cutaneous Myxoid Neoplasms With Histopathologic Overlap.

Superficial angiomyxomas (SAMs) are benign cutaneous tumors that arise de novo and in the setting of the Carney complex (CC), an autosomal dominant disease with several cutaneous manifestations including lentigines and pigmented epithelioid melanocytomas. Although most SAM do not pose a diagnostic challenge, a subset can demonstrate histopathologic overlap with other myxoid tumors that arise in the skin and subcutis. Traditional immunohistochemical markers are of limited utility when discriminating SAM from histopathologic mimics. Since protein kinase A regulatory subunit 1 alpha (PRKAR1A) genetic alterations underlie most CC cases, we investigated whether SAM demonstrate loss of PRKAR1A protein expression by immunohistochemistry. In our series, 29 SAM, 26 myxofibrosarcoma, 5 myxoid dermatofibrosarcoma protuberans, 11 superficial acral fibromyxomas, and 18 digital mucous cysts were characterized. Of the 29 SAM examined in this study, 1 was associated with documented CC in a 5-year-old girl. SAM tended to arise in adults (mean 49.7 y; range: 5 to 87 y). Loss of PRKAR1A was seen in 55.2% of cases (16/29) and had a male predilection (87.5%, 12/16). PRKAR1A-inactivated SAM demonstrated significant nuclear enlargement (100%, 16/16 vs. 23.1%, 3/13), multinucleation (81.3%, 13/16 vs. 23.1%, 3/13), and presence of neutrophils (43.8%, 7/16 vs. 0%, 0/13). In contrast, PRKAR1A was retained in all cases of myxofibrosarcoma (100%, 26/26), myxoid dermatofibrosarcoma protuberans (100%, 5/5), superficial acral fibromyxomas (100%, 11/11), and digital mucous cyst (100%, 18/18). Taken together, PRKAR1A loss by immunohistochemistry can be used as an adjunctive assay to support the diagnosis of SAM given the high specificity of this staining pattern compared with histopathologic mimics.

Alteration of PDGFRß-Akt-mTOR pathway signaling in fibrosarcomatous transformation of dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a cutaneous mesenchymal tumor of intermediate malignancy and fibroblastic/myofibroblastic differentiation. Fibrosarcomatous (FS) component is a high-grade component of DFSP. The detailed oncogenic difference between DFSP and FS components is not clear. We thus investigated the Akt-mTOR pathway in both components. We used 65 tumor samples obtained from 65 patients. The phosphorylation of Akt-mTOR pathway proteins (Akt, mTOR, 4EBP1, and S6RP) and PDGFRα/ß was assessed by immunohistochemical staining, the results of which were confirmed by Western blotting. The immunohistochemical results were as follows: in ordinary DFSP components, p-PDGFRα-positive tumors were 41.9% (18/43 cases), p-PDGFRß 55.8% (24/43 cases), p-Akt 51.2% (22/43 cases), p-mTOR 39.5% (17/43 cases), p-4EBP1 46.5% (20/43 cases), and p-S6RP 41.8% (18/43 cases); in DFSP components of FS-DFSP, 52.6% (10/19 cases), 47.4% (9/19 cases), 52.6% (10/19 cases), 36.8% (7/19 cases), 52.6% (10/19 cases), and 52.6% (10/19 cases); and in FS components, 45.5% (10/22 cases), 36.4% (8/22 cases), 72.7% (16/22 cases), 54.5% (12/22 cases), 72.7% (16/22 cases), and 68.2% (15/22 cases), respectively. There were significant positive correlations of the phosphorylation of most of the Akt-mTOR pathway proteins (p-Akt, p-mTOR, p-4EBP1, and p-S6RP) with each other (P < .05). Phospho-PDGFRß was well correlated with the phosphorylation of Akt-mTOR pathway proteins in DFSP components of ordinary and FS-DFSPs, but these correlations were weaker in FS components. This study suggested the association of activation of Akt-mTOR pathway proteins and PDGFR with the progression of DFSP to FS. The Akt-mTOR pathway is thus a potential therapeutic target in imatinib-resistant DFSP/FS.

Expression of MMP-2, MMP-9 and MMP-11 in dermatofibroma and dermatofibrosarcoma protuberans.

Dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) are the spindle cell mesenchymal neoplasms of the dermis and subcutis. Their histogenesis still remains uncertain and controversial. Traditionally, CD34 and factor XIIIa or other markers have been widely used to distinguish these two diseases. However, the results of these markers reveal overlapping and they lack specificity. Formalin-fixed, paraffin-embedded blocks were collected from the biopsied cases in Kaohsiung Medical University Hospital in Taiwan between 2004 and 2006. This study included 19 cases of DF and 17 cases of DFSP. Immunohistochemical analysis using antibodies CD34, matrix metalloproteinases (MMP)-2, MMP-9, and MMP-11 was performed. We found that the expression of CD34, MMP-2 and MMP-11 shows significant statistical differences in Immunohistochemistry (IHC) study positive or negative reactivity (positive of CD34 in DFSP and positive of MMP-2 and MMP-11 in DF; p=0.03, p<0.001, and p<0.001, respectively) between DF and DFSP. The result for expression of MMP-9 reveals no differences. The results indicate that the pathogenesis of DF and DFSP are affected by different expressions of extracellular matrix proteins. Metalloproteinases may play a direct role in these two diseases. Since no single marker can completely distinguish DF from DFSP, a combination of more than two or three stains may elevate the accuracy of diagnosis.

Dermatofibrosarcoma protruberans treatment with platelet-derived growth factor receptor inhibitor: a review of clinical trial results.

PURPOSE OF REVIEW: Dermatofibrosarcoma protuberans (DFSP) is a rare mesenchymal neoplasm arising in the dermis, accounting for less than 0.1% of all cancers. Given its rarity, and paucity of randomized trials, the nuances of treatment are not widely understood. In this review we attempt to summarize the available data to guide treatment choices for physicians managing this disease. RECENT FINDINGS: DFSP carries a translocation of chromosomes 17 and 22 leading to juxtaposition of the collagen type-1α1 promoter to the platelet-derived growth factor (PDGF) gene. This results in unregulated expression of PDGF leading to autocrine or paracrine activation of its receptor (PDGFRß). This molecular pathway is the target of our current drug therapy for DFSP, imatinib, a tyrosine kinase inhibitor that interferes with the phosphorylation and activation of PDGFRß. In case reports and prospective studies, imatinib was noted to be an effective treatment for patients with unresectable or metastatic DFSP, associated with response rates approaching 50%. It has also been used preoperatively to improve the resectability of tumors. Since metastasis is rarely seen and local recurrences are uncommon following wide excision with pathologically negative margins, surgery remains the backbone of treatment. SUMMARY: Imatinib, a tyrosine kinase inhibitor, is the current preferred agent for treatment of unresectable or metastatic DFSP. Clinical trials evaluating broader-spectrum kinase inhibitors such as pazopanib are in development.

Cyclooxygenase-2 expression in dermatofibroma and dermatofibrosarcoma protuberans.

BACKGROUND: Dermatofibroma (DF) and dermatofibrosarcoma protuberans (DFSP) occasionally resemble each other histologically but differ in histogenesis and biological behavior. This study sought to determine if these lesions can be differentiated by the quantity or quality of expression of cyclooxygenase-2 (COX-2), an enzyme associated with both reactive and neoplastic processes. PATIENTS AND METHODS: Formalin-fixed and paraffin-embedded samples from 20 DFs and 20 DFSPs were stained immunohistochemically with antibodies directed against COX-2. Staining was evaluated semiquantitatively for percentage and intensity using a three-tiered system. DFs were graded and analyzed by cellularity. Findings within the tumors were compared with fibrocyte staining in adjacent tissue. The results were analyzed. RESULTS: Nineteen DFs (95%) and 15 DFSPs (75%) were immunopositive for COX-2; this difference was not statistically significant. Highly cellular DFs showed more widespread (p = 0.0039; r = 0.614) and more intense (p = 0.0586; r = 0.429) staining than less cellular DFs and more prominent staining in adjacent fibroblasts (p = 0.044; r = 0.608). CONCLUSIONS: COX-2 immunostaining does not distinguish DFs from DFSPs. However, the enzyme is expressed more widely and more intensely in more cellular, possibly younger, DFs. The prominent expression of COX-2 in DFSP may have clinical implications for treatment with COX-2 inhibitors in tumors that are not amenable to surgery.

Immunohistochemical expression of matrix metalloproteinases 1, 2, 9, and 14 in dermatofibrosarcoma protuberans and common fibrous histiocytoma (dermatofibroma).

CONTEXT: Common fibrous histiocytoma (cFH) or dermatofibroma and dermatofibrosarcoma protuberans (DFSP) are 2 spindle cell mesenchymal tumors that are distinguished in part by their microscopic growth patterns and clinically by the greater propensity for DFSP to recur. Matrix metalloproteinases (MMPs) potentially play a role in modulating the growth patterns of cFH and DFSP by remodeling the extracellular matrix. OBJECTIVE: To evaluate the immunohistochemical (IHC) expression of MMP-1, MMP-2, MMP-9, and MMP-14 in DFSP and cFH, because (1) MMP-1, MMP-2, MMP-9, and MMP-14 are synthesized by dermal fibroblasts, the major constituent of DFSP and cFH; and (2) platelet-derived growth factor B, which is overexpressed in most examples of DFSP because of t(17;22), activates ets-1, a transcription factor that regulates molecules associated with tumor invasion and metastasis, including MMP-1, MMP-3, and MMP-9. DESIGN: Immunohistochemical studies were performed on archived, formalin-fixed, paraffin-embedded tissue of DFSP (n = 48) and cFH (n = 47).Results.-Significant IHC expression (>10% of tumor cells) in cFH included MMP-14 (27 [59%] of 46 tumors positive), MMP-2 (21 [47%] of 45 tumors positive), MMP-9 (9 [20%] of 45 tumors positive), and MMP-1 (6 [13%] of 46 tumors positive). No DFSPs showed significant IHC expression of any of the MMPs evaluated. However, anti- MMP-2 highlighted a rich microvascular element within deep tumor tissue present in 81% of DFSPs with a prominent subcutaneous component. CONCLUSION: Our IHC results indicate that MMP-1 and MMP-9 are not up-regulated in DFSP. Convincing expression of MMP-14 in cFH suggests that this MMP may affect the growth pattern of the lesion, perhaps by activating MMP-2 expression in tumor cells. In DFSP, MMP-2 may play a role in tumor angiogenesis.

Mitogenic activity of dermatofibrosarcoma protuberans is mediated via an extracellular signal related kinase dependent pathway.

Dermatofibrosarcoma protuberans is a malignant mesenchymal tumor originating in the dermis. Although it is locally aggressive and recurs unless completely excised, it only rarely metastasizes. In this study, we investigated the mechanisms of increased proliferation of dermatofibrosarcoma protuberans cells. The cells showed increased DNA synthesis in serum-free medium, which was demonstrated by the incorporation of [3H]-thymidine. Increased DNA synthesis of dermatofibrosarcoma protuberans cells was abolished by genistein, a tyrosine kinase inhibitor, or by PD98059, a specific extracellular signal related kinase pathway inhibitor, but not by calphostin C, a protein kinase C inhibitor. Immunoblotting analysis of dermatofibrosarcoma protuberans cells using a specific antibody against phosphorylated extracellular signal related kinase (Thr202/Tyr204) showed that extracellular signal related kinase was expressed as constitutively phosphorylated molecules in dermatofibrosarcoma protuberans cells. Immunofluorescence analysis showed that the kinase was constitutively located in the nucleus of the cells. Furthermore, transfection of the dominant negative mutant extracellular signal related kinase into dermatofibrosarcoma protuberans cells abolished the increased mitogenic activity of the cells. These results suggest that an extracellular signal related kinase dependent pathway is implicated in the increased mitogenic activity of dermatofibrosarcoma protuberans cells.

Tyrosinase expression in malignant melanoma, desmoplastic melanoma, and peripheral nerve tumors.

CONTEXT: Pathologists may encounter problems in the differential diagnosis of malignant melanoma, spindle and epithelioid neoplasms of peripheral nerves, and fibrohistiocytic tumors. Tyrosinase has been demonstrated to be a sensitive marker for melanoma. OBJECTIVE: To determine the specificity of tyrosinase expression in the differential diagnosis of melanoma, desmoplastic melanoma, and peripheral nerve sheath tumors. DESIGN: Immunoreactivity for tyrosinase, HMB-45 (anti-gp100 protein), S100 protein, CD34, and vimentin was studied in 70 tumors, including 15 melanomas (5 desmoplastic, 4 amelanotic, 6 melanotic), 13 malignant peripheral nerve sheath tumors; 10 schwannomas (1 pigmented), 12 neurofibromas (4 pigmented), and 20 fibrohistiocytic tumors (10 dermatofibrosarcoma protuberans and 10 dermatofibromas). Microwave-based antigen retrieval was performed in 10mM citrate buffer, pH 6.0, for 20 minutes at 121 degrees C. RESULTS: All melanomas demonstrated positive immunostaining for tyrosinase, HMB-45, and S100 protein. Immunoreactivity for HMB-45 was generally stronger than that for tyrosinase in amelanotic lesions and significantly stronger in 1 of the desmoplastic lesions. The 4 pigmented neurofibromas were focally positive for tyrosinase, but did not stain for HMB-45. The pigmented schwannoma was focally positive for both tyrosinase and HMB-45. The malignant peripheral nerve sheath tumors, dermatofibrosarcoma protuberans, and dermatofibromas were nonreactive for tyrosinase and HMB-45. CONCLUSIONS: Our results support the sensitivity of tyrosinase expression and demonstrate the relative specificity of tyrosinase as a marker for melanocytic lesions, including desmoplastic melanoma, although pigmented peripheral nerve tumors may demonstrate focal positive staining. Immunoreactivity for tyrosinase and HMB-45 may have been enhanced by the microwave-based antigen-retrieval technique used in this study.

Expression of the CD10 antigen (neutral endopeptidase) by mesenchymal tumors of the skin.

BACKGROUND: The CD10 (or CALLA) antigen is a neutral endopeptidase expressed by a variety of non-hemopoietic cells, including fibroblasts in various tissues. So far little or conflicting data exist concerning the expression of CD10 in normal and pathologic skin. METHODS: We investigated the immunohistochemical expression of the CD10 antigen on formalin-fixed, paraffin-embedded tissue specimens of normal skin and 162 cutaneous proliferative lesions, mostly mesenchymal tumors. RESULTS: In normal skin CD10 immunoreactivity was found in periadnexal mesenchymal cells. In skin tumors, CD10+ cells were found mainly in dermatofibromas and, to a lesser extent, in Dermatofibrosarcoma protuberans and neurofibromas. Metastatic (and to a lesser extent primary) melanomas also occasionally expressed CD10. CONCLUSION: Our results show that the CD10 antigen is expressed by mesenchymal cells of normal human dermis, presumably encompassing a subset of CD34+ dermal dendrocytes and/or periadnexal fibroblasts. The CD10 antigen could be used as an adjunct to the diagnosis of some spindle-cell cutaneous tumors such as dermatofibromas and Dermatofibrosarcoma protuberans, but its value as a single marker is rather limited. The possible role of CD10 as a progression marker in melanoma is interesting and merits further study.

Expression of cathepsins in dermal fibrous tumors: an immunohistochemical study.

Cathepsins are lysosomal proteases that are distributed in many normal tissues and are primarily responsible for intracellular catabolism and turnover. The increased level of cathepsins in tumors together with their ability to degrade extracellular matrix proteins has led to the hypothesis that they are involved in the process of invasion and metastasis. We studied immunohistochemically the expression of cathepsins B, pro-D and pro-L in 8 cases of dermatofibrosarcoma protuberans (DFS), five cases of atypical fibroxanthoma (AFX) and twenty cases of dermatofibroma (DF). Expression of cathepsins B and pro-D could be detected in 5 of the 8 cases (62.5%) of DFS, whereas cathepsin pro-L was found in 4 (50%) cases. All AFX expressed cathepsin pro-L, whereas cathepsins B and pro-D were observed in 4 out of 5 cases. None of the malignant tumors showed a recurrence or metastasis after a period of four years. We found no expression of cathepsins in DF. In the epidermis and appendages, an expression of cathepsins pro-D, pro-L and B was seen. We conclude that cathepsins may be markers of increased metabolism rather than specific markers of malignancy.