[A hard subcutaneous swelling: not always as malignant as it seems]. / Een harde onderhuidse bult.

BACKGROUND: Nodular fasciitis is a rare, benign soft tissue tumor in young adults on the arms or trunk. CASE DESCRIPTION: A 24-year-old woman with previous pretibial melanoma in situ presented with a painless, rapidly growing subcutaneous hard swelling on the right forearm since two weeks. Ultrasound showed a subcutaneous, irregularly shaped, vascularized mass, suspicious for malignancy. Three days later, the swelling had subsided spontaneously. A new ultrasound showed a smaller, oval, sharply demarcated lesion with an inflammatory aspect. Histopathological-immunohistochemical examination of a biopsy showed a spindle cell lesion consisting of (myo)fibroblasts with some erythrocyte extravasation, consistent with nodular fasciitis. Three months later the nodule was resolved spontaneously without treatment. CONCLUSION: Nodular fasciitis should be included in the differential diagnosis in case of hard, fast-growing, subcutaneous bumps in young adults. By ultrasound, it is difficult to differentiate from a malignant soft tissue tumor. A biopsy is necessary to confirm the diagnosis with certainty.

Solitary fibrous tumor - clinicopathologic, immunohistochemical and molecular analysis of 28 cases.

BACKGROUND: Solitary fibrous tumor is a mesenchymal tumor of fibroblastic type, which can affect any region of the body. Recently, a recurrent gene fusion NAB2-STAT6 has been identified as molecular hallmark. The NAB2-STAT6 fusion leads to EGR1 activation and transcriptional deregulation of EGR1-dependent target genes and is a driving event in initiation of SFT. In this study, we report the clinicopathologic and RT-PCR findings and evaluated expression of STAT6 and EGR1 protein in a cohort of 28 SFTs. METHODS: 28 patients with a median age of 54 years were included with SFTs originating at different sites, most occurring in the lung and pleura (9, 32%), 5 in soft tissues of the lower extremities (18%) and 5 in the head and neck (18%). For detection of the NAB2-STAT6 fusion gene, RT-PCR was performed using RNA extracted from formalin-fixed and paraffin-embedded tissues. Immunohistochemistry was performed on all cases with antibodies against STAT6 and EGR1. RESULTS: All patients were treated by surgery, 3 with adjuvant chemo- or radiotherapy. Follow-up data of 18 patients could be obtained of which 2 patients died of metastatic disease 13 months and 52 years after first diagnosis. Sixteen patients have no evidence of disease with a median follow up of 29.5 months (range 7 - 120 months). NAB2-STAT6 fusion transcripts were found in 19/28 cases (68%). The most common fusion was between NAB2 exon 4 and STAT6 exon 3 (11/19, 58%), mainly occurring in pleuropulmonary lesions. All cases showed strong nuclear expression of STAT6 (28/28, 100%) while EGR1 showed low-level variable nuclear expression in all samples, comparable with the EGR1 expression results of the control group. CONCLUSIONS: The identification of the NAB2-STAT6 fusion in SFTs can provide important diagnostic information, especially in cases with aberrant morphology or when biopsy material is limited. STAT6 immunohistochemistry is another useful tool in diagnosing SFT. EGR1 immunohistochemistry indicates low-level protein expression in accordance with EGR1 activation due to distorted NAB2 activity. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/13000_2014_224.

Epithelioid Hemangioendothelioma: clinicopathologic, immunhistochemical, and molecular genetic analysis of 39 cases.

BACKGROUND: Epithelioid hemangioendothelioma is a malignant, often indolent vascular tumor which occurs at various anatomic sites. Based on a reciprocal translocation t (1;3)(p36;q25), a consistent WWTR1-CAMTA1 fusion gene has been found. An alternate YAP1-TFE3 fusion has been detected in a small and distinct subset of cases. METHODS: Thirty-nine tumors, from 24 females and 15 males with an age range 9-85 years, were located in soft tissue (head and neck [8], trunk [5], upper extremities [3], lower extremities [2], mediastinal [1], and paratesticular [1]), lymph node (1), breast (1), skin (2), bone (6), lung (7), and liver (2). The cases were investigated using a panel of immunohistochemical markers. The aforementioned fusion-genes were examined using RT-PCR and/or FISH in order to validate their diagnostic value. RESULTS: Follow-up available for 17 patients ranged from 3 months to 7 years (median interval 1.5 years). Eleven patients were alive without disease, 2 patients were alive with disease after 1.5 and 2 years, respectively. Four patients died of disease after 4 months (n = 1), 5 months (n = 2), and 1.5 years (n = 1).The size, known for 30 lesions, was >3 cm in 9 of them. Histologically, all lesions had classical features, at least focally. Four tumors counted >3 mitoses/50 HPF. Immunohistochemically, all cases tested stained positive for ERG (21), FLI1 (5) and CD31 (39). CD34 and D2-40 positivity was seen in 81% and 71% of the examined cases, respectively. 11/35 cases expressed pan-keratin and 6/20 cases CK8.18. TFE3 showed a nuclear reaction in 21/24 cases, irrespective of TFE3 rearrangement.Molecular genetically, 35/35 cases revealed one of the fusion genes by FISH and/or RT-PCR with WWTR1-CAMTA1 in 33 cases and YAP1-TFE3 in 2 cases. CONCLUSIONS: These results demonstrate the high diagnostic value of FISH and RT-PCR in detecting the fusion genes of EHE. The immunohistochemical utility of TFE3 appears questionable in this study. VIRTUAL SLIDES: The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/4010279141259481.