A low-grade malignant soft tissue tumor with S100 and CD34 co-expression showing novel CDC42SE2-BRAF fusion with distinct features.

Recently, a novel group of spindle cell tumors defined by S100 and CD34 co-expression harboring recurrent fusions involving RET, RAF1, BRAF, and NTRK1/2 gene has been identified. Morphologically, they are characterized by monomorphic neoplasm cells, "patternless" growth pattern, stromal, and perivascular hyalinization, lacked necrosis. We reported a 52-year-old Chinese female patient with a S100 and CD34 co-expression sarcoma presenting in the right proximal forearm. The forearm mass initially emerged 19 months ago when it was misdiagnosed as a solitary fibrous tumor and was surgically removed without further treatment. Microscopically, the primary and the recurred tumors share the same features, resembling the morphology of the recently characterized group. Nevertheless, some distinct features, such as predominantly epithelioid tumor cells and focally staghorn vessels, were also present in our case. Genomic profiling with clinical next-generation sequencing was performed and revealed CDC42SE2-BRAF gene fusion, MET amplification, and CDKN2A/B deletion. Both FISH and nested RT-PCR were performed to confirm the gene fusion. The patient was treated with crizotinib for two cycles but showed no obvious benefit. The presented case adds to the spectrum of the novel, characterized solid tumors, and provides suggestions for emerging therapeutic strategies for precision medicine involving targeted kinase inhibitors.

Inflammatory myofibroblastic tumor arising from soft tissues of extremities harboring a novel CLIP2-ALK fusion.

A 34-year-old Chinese woman found a lump in her left leg for more than 3 weeks without any discomfort. Grossly, the tumor was relatively well delineated with focal infiltration. Histopathologic evaluation showed a compact fascicular spindle cell proliferation with variable myxoid and collagenous stroma and scattered inflammatory infiltrate. Immunohistochemically, the tumor cells showed positive expression of ALKD5F3 and SMA and negative expression of CD34, desmin, and cytokeretin. Fluorescence in situ hybridization analysis of the ALK locus showed break-apart signals in 20% of tumor cells, and DNA sequencing discovered a novel CLIP2-ALK fusion gene. The lesion was diagnosed as an inflammatory myofibroblastic tumor (IMT). To the best of our knowledge, this is the first case with CLIP2-ALK gene fusion in the somatic soft tissue IMTs.

[Solid variant of angiomatoid fibrous histocytoma:report of 3 cases].

OBJECTIVE: To study the clinicopathologic features, immunophenotype, molecular genetics and differential diagnosis of solid variant of angiomatoid fibrous histocytoma. METHODS: The clinicopathologic features of 3 cases of solid variant of angiomatoid fibrous histocytoma were analyzed and the literature was reviewed. RESULTS: There were a total of 2 males and 1 female. The age of patients ranged from 9 to 12 years. The patients presented with a painless mass located in left forearm, left knee or back. The lesions were treated by complete surgical resection. On gross examination, the tumors varied from 1.6 cm to 4.5 cm in greatest dimension. They were well-circumscribed and had pale yellow to grayish-red solid cut surface. Histologically, the tumor was composed of histocytoid cells arranged in sheet-like pattern. A fibrous pseudocapsule surrounded by lymphocytes and plasma cells was identified. Immunohistochemical study showed that the tumor cells in all cases were positive for vimentin and CD68. They were negative for S100 protein, cytokeratin, CD34, CD31, smooth muscle actin, CD35, CD21 and CD30. Two cases also expressed CD99 and one of them was positive for desmin and epithelial membrane antigen. Fluorescence in-situ hybridization was positive for EWSR1 gene. CONCLUSIONS: Solid type represents a variant of angiomatoid fibrous histocytoma and is considered as tumor of borderline malignant potential. Definitive diagnosis requires thorough histologic examination and clinical correlation. Immunohistochemistry and EWSR1 gene study are helpful in further delineation and differential diagnosis. Complete resection or wide local excision with post-operative follow up is the main modality of treatment.

[Epithelioid hemangioma: a clinicopathologic analysis of 7 cases].

OBJECTIVE: To study the clinicopathologic features, diagnosis and differential diagnosis of epithelioid hemangioma. METHODS: The morphologic features of 7 cases of epithelioid hemangioma of skin, bone and venous vessels were studied. RESULTS: There were altogether 4 male and 3 female patients (median age = 34 years; age range from 14 to 54 years). The 3 skin cases presented as single or multiple erythematous to bluish nodules or papules, with or without itchiness. The 2 bone cases appeared as osteolytic expansile lesions on radiologic examination. The remaining 2 cases involved medium-sized venous structures and presented as small isolated nodules in soft tissue. Histologically, the lesions were characterized by the presence of exuberant endothelial proliferations with various degree of inflammatory reaction. The neoplastic endothelial cells were plump, eosinophilic and polygonal, forming vascular channels. Occasional solid sheet-like arrangement was demonstrated. Intracytoplasmic vacuoles were commonly identified, indicating formation of primary lumen. The surrounding stroma contained various number of eosinophils and lymphoplasmacytic cells. Immunohistochemical study showed that the tumor cells were positive for endothelial markers (CD31 and CD34) and negative for epithelial marker (cytokeratin). Follow-up information was available in 6 cases. The duration of follow-up ranged from 5 to 36 months (median = 14 months). There was no evidence of recurrence or distant metastasis. CONCLUSIONS: Epithelioid hemangioma is a rare benign curable lesion which can be multifocal, involving skin, soft tissue and bone. It needs to be distinguished from Kimura's disease and epithelioid hemangioendothelioma.

Prognostic analysis of extrameningeal solitary fibrous tumor using the modified Demicco model: a clinicopathologic study of 111 Chinese cases.

Introduction: Solitary fibrous tumor (SFT) represents a fibroblastic neoplasm exhibiting NAB2::STAT6 gene rearrangement, displaying diverse clinical manifestations, spanning from benign to malignant. To predict prognosis, the modified (four-variable) Demicco (mDemicco) model was introduced. This investigation aims to authenticate the mDemicco risk model's precision in Asian patients while investigating the clinicopathological and molecular factors linked to the prognosis of extrameningeal SFTs. Methods: Clinicopathological data from 111 extrameningeal SFT cases in East China, covering the period from 2010 to 2020, were thoroughly analyzed. The tumors were classified using the mDemicco model. Immunohistochemical evaluation of P16 and P53, molecular detection of TP53 and TERT promoter mutation, and fluorescence in situ hybridization for CDKN2A gene alterations were performed. Statistical methods were utilized to assess the associations between clinicopathological or molecular factors and prognosis. Results: Histologically, only one parameter, the mitotic count, exhibited a statistical correlation with progression-free survival (PFS) and overall survival (OS). During the Kaplan-Meier analysis, the variation in PFS among the different risk groups exhibited a notable trend towards statistical significance. Nevertheless, 3 out of 74 patients classified as low-risk SFTs and 7 out of 21 patients classified as intermediate-risk exhibited disease progression. Among the 5 patients with TP53 mutations and/or mutant-type P53 immunophenotype, 3 experienced disease progression, including 2 intermediate-risk patients. Additionally, among the 4 patients with TERT promoter mutations who were followed up, 3 showed progression, including 2 intermediate-risk patients. Moreover, it was observed that hemizygous loss of CDKN2A was detected in more than 30% of one case, yet the patient exhibited a favorable survival outcome. Conclusion: The mDemicco risk model exhibits certain limitations when dealing with smaller tumor sizes, younger age groups, and occurrences of malignant and dedifferentiated SFTs. Furthermore, molecular factors, such as TP53 or TERT promoter mutations, may identify intermediate-risk SFTs with poorer prognoses.

[Primary intermediate hemangioendothelioma of bone: a study of 5 cases].

OBJECTIVE: To study the radiologic and pathologic features of primary intermediate hemangioendothelioma of the bone. METHODS: Five cases of primary intermediate hemangioendothelioma of bone encountered in the past three years were enrolled into the study. The clinical, radiologic, pathologic and immunohistochemical features of the tumors were reviewed. RESULTS: The patients included 3 children with Kaposiform hemangioendothelioma and 2 elderly with retiform hemangioendothelioma. Four of the cases affected long bones and the remaining case affected the clavicle. One case showed multifocal involvement of the humerus. Radiologically, the tumors showed borderline to low-grade bony destruction, with various degrees of cortical defect. Intralesional or perilesional bone formation was demonstrated in 4 cases and radial spicules were seen in 1 case. The histopathologic features of primary intermediate hemangioendothelioma of bone were similar to those of soft tissue, except for the presence of reactive bone formation. Immunohistochemically, the tumor cells were positive for CD31 (5/5), CD34 (5/5), vimentin (5/5) and smooth muscle actin (3/5) but negative for cytokeratin and epithelial membrane antigen. CONCLUSIONS: Primary intermediate hemangioendothelioma of bone is a distinct entity and similar histologic classification applies as in its soft tissue counterparts. Comparison of the biologic behavior requires long-term follow-up studies.

Case report: ALK-rearranged spindle and epithelioid cell neoplasms with S100 and CD34 co-expression: Additional evidence of kinase fusion-positive soft tissue tumors.

ALK rearrangements have rarely been reported in S100- and CD34-co-expressing soft tissue neoplasms with lipofibromatosis-like neural tumor (LPFNT) pattern or stromal and perivascular hyalinization, mimicking NTRK-rearranged spindle cell tumors. Here, we reported ALK fusions involving related partner genes in two adult soft tissue tumors with S100 and CD34 co-expression, and conducted a literature review of mesenchymal tumors harboring ALK or other kinase fusions. Case 1 was a 25-year-old female who underwent excision of a soft tissue mass in the anterior thigh region. Morphologically, the tumor was composed of spindle cells adjacent to epithelioid cells embedded in myxedematous and hyalinized stroma, with infiltrative boundary. Spindle cells mixed with inflammatory infiltration resembling inflammatory myofibroblastic tumor (IMT) were seen sporadically. However, brisk mitosis and focal necrosis was also observed, indicating an intermediate-grade sarcoma. In case 2, the left side of the neck of a 34-year-old man was affected. The tumor was composed of monomorphic spindle cells arranged in fascicular growth or patternless pattern, with stromal and perivascular hyalinization. Sparse inflammatory cell infiltration was also observed. Both tumors showed CD34, S100, and ALK-D5F3 immunoreactivity. Next generation sequencing (NGS) test identified a PLEKHH2::ALK fusion in case 1, which was confirmed by RT-PCR and Sanger sequencing, whereas the RT-PCR (ARMS method) test detected an EML4::ALK fusion in case 2. In conclusion, this study expands the morphological and genetic landscape of tumors with S100 and CD34 co-expression harboring kinase fusions, and suggests that kinase fusion-positive mesenchymal neoplasms are becoming an enlarging entity with a variety of morphological patterns.

[Adult prostate sarcoma: a clinicopathologic study of 15 cases].

OBJECTIVE: To clarify the clinical and morphological features of adult prostate sarcoma (APS) and to further improve the knowledge and diagnostic accuracy for APS. METHODS: Fifteen cases of APS were observed and analyzed on the clinical symptom, pathological features, treatment and prognosis. RESULTS: Age of onset ranged from 22 to 77 years (mean 46.3 years). The majority of cases were presented with dysuresia. By digital rectal examination and imaging of the prostate, APS was often identified as a large tumor mass. There were 6 cases of leiomyosarcomas, 6 embryonal rhabdomyosarcomas, and 3 fibrosarcomas in this series. Follow-up data were available for 12 cases: 7 cases died of the disease between 9 days and 360 days after surgery. Among 5 survived patients, 3 cases had recurrence after 2 to 24 months follow-up. CONCLUSIONS: APS is a rare tumor that typically has clinical features: earlier age of onset, fast-appeared urinary tract symptoms, significant mass effects, and poor outcome. Level of prostate specific antigen (PSA) is usually normal or lower. Final diagnosis relies on the features of histology and immunohistochemistry expression profile.

[EZH2 expression in human prostate cancer and its clinicopathologic significance].

OBJECTIVE: To investigate the expressions of the EZH2 protein and EZH2 mRNA in human prostate cancer (PCa) and their correlation with the clinicopathologic parameters. METHODS: A tissue microarray (TMA) was constructed, which contained 48 dots of formalin-fixed paraffin-embedded tissue samples of human PCa. The expressions of the EZH2 protein and EZH2 mRNA in the samples were detected by immunohistochemistry (EnVision) and in situ hybridization (ISH). Another 15 cases of human benign prostate hyperplasia (BPH) and 12 cases of human prostate intraepithelial neoplasia (HGPIN) were taken as controls. RESULTS: The positive rates of the EZH2 protein and mRNA were significantly higher in PCa than in BPH and HGPIN (87.5% vs 13.33% and 16.67%, 81.25% vs 6.67% and 16.67%, P < 0.05). The positive expression of the EZH2 protein was 96.67% and 72.22% in the Gleason score > or = 7 and Gleason score < or = 6 groups, respectively, with significant differences between the two groups (P < 0.05). The positivity of the EZH2 protein was significantly related to the TNM stage, increasing with tumor progression (P < 0.05), but not to age and serum PSA (P > 0.05), and so was that of EZH2 mRNA to TNM stage (P < 0.05), but not to age, serum PSA and Gleason score (P > 0.05). When the above characteristics were regarded as two-level discrete variables, both the EZH2 protein and EZH2 mRNA showed statistically significant differences in the positive expression rate (P < 0.05). CONCLUSION: The over-expressions of the EZH2 protein and EZH2 mRNA may play an important role in the pathogenesis and progression of PCa and provide some reference indexes for estimating the malignancy, progression and prognosis of PCa.

[Clinicopathologic features and prognostic significance of basal-like breast cancer].

OBJECTIVE: To analyzed a large group of invasive breast cancers with long-term follow-up information to evaluate the clinicopathologic, morphological and prognostic features of basal-like breast cancers in Chinese population. METHODS: Immunohistochemistry was used to detect the expression of ER, HER2, CK5/6, EGFR on tissue microarray with 1311 invasive breast cancers. Based on the results, these cases were categorized into luminal A, luminal B, basal-like, HER2-overexpressing and null subtypes. Clinicopathological features and survival rates were compared between these groups. RESULTS: Basal-like breast cancers constituted 17.0% of 1311 invasive breast cancers with a significantly larger size, higher grade and higher incidence of the medullary carcinoma, frequent recurrence and infrequent node metastasis. Morphologically, basal-like breast cancers showed a significantly more solid architecture and ribbon-like architecture associated with necrosis (more geographic necrosis) and central scar, a more pushing margin, lymphocytic infiltration and a higher mitosis score, more syncytial growth, presence of basaloid cells, spindle cells and squamous metaplasia. The disease-free survival and overall survival of basal-like breast cancers were significantly poorer than that of luminal A subtype, but similar to the other ER-negative subtypes. Basal markers were not independent prognostic factors. CONCLUSIONS: Basal-like breast cancers in Chinese population has a similar prevalence to that of the western populations. They have distinct clinicopathologic features compared to other non-basal breast cancers, but overlapping with other ER-negative breast cancers. Morphological features are strongly associated with basal-like breast cancers although they are not very specific. The survival of basal-like breast cancers is poorer than luminal A, but similar to the other ER-negative breast cancers, and basal markers are not independent prognostic factors of breast cancers.

[Clinicopathologic characteristics of hemangiopericytoma/solitary fibrous tumor with giant cells].

OBJECTIVE: To study the pathological characteristics, diagnosis and differential diagnoses of hemangiopericytoma-solitary fibrous tumor with giant cells. METHODS: Pathological characteristics of seven cases of orbital and extraorbital hemangiopericytoma-solitary fibrous tumors with giant cells were evaluated by HE and immunohistochemistry (EnVision method). RESULTS: Two cases were located in the orbit, one of which had recurred. Five cases were located in the extraorbital regions. Histologically, the tumors were well-circumscribed and composed of non-atypical, round to spindle cells with collagen deposition in the stroma. The tumors had prominent vasculatures and in areas, pseudovascular spaces lined by multinucleated giant cells lining which were also present in the stroma. Immunohistochemically, both neoplastic cells and multinucleate giant cells expressed CD34. Seven patients underwent tumor excision and were well and without tumor recurrence upon the clinical follow-up. CONCLUSIONS: Hemangiopericytoma-solitary fibrous tumor with giant cells is an intermediate soft tissue tumor. It typically involves the orbital or extraorbital regions. Histologically, the tumor should be distinguished from giant cell fibroblastoma, pleomorphic hyalinzing angiectatic tumor of soft part and angiomatoid fibrous histiocytoma.

[Roles of immunohistochemistry in prognostic assessment of basal-like breast cancer].

OBJECTIVES: Basal cell-like breast cancer is one of the subtypes using molecular typing, and this subtype attracted a wide spread attention. Currently, no uniform diagnostic criteria are available. Most studies demonstrated poor outcomes, but contradictory conclusions appeared recently. The prognosis of basal cell-like breast cancer using different immunohistochemical criteria were analyzed. METHODS: Two hundred and eighty-four invasive breast cancers with a follow-up information over 5 years were evaluated for ER, PR, HER2, CK5/6, CK14, EGFR expression on tissue microarray immunohistochemically. Based on the results, these cases using four different diagnostic criteria were categorized, namely: Nielsen (ER-/HER2-, CK5/6+ and/or EGFR+), Kim (ER-/PR-/HER2-, CK5/6+ and/or CK14+ and/or EGFR+), Triple-negative (ER-/PR-/HER2-), and basal-CK (CK5/6+ and/or CK14+). 5-year survival information was compared between groups. RESULTS: The prevalence of basal cell-like breast cancer by Nielsen, Kim, Triple-negative and basal-CK were 15.5% (44/284), 14.8% (42/284), 43.3% (123/284) and 21.1% (60/284) respectively; the recurrence rates were 18.2% (8/44), 21.4% (9/42), 10.6% (13/123) and 11.7% (7/60) respectively. These were higher than recurrence rates for other subtypes, but only the differences by Nielsen's and Kim's criteria were significant. Using Nielsen's and Triple-negative's criteria, basal-like tumors showed shorter 5-year disease-free survival (both P < 0. 01) and overall survival (P < 0.05 and 0.01) than luminal A subtype, using Kim's criteria, basal-like tumors showed a lower 5-year disease-free but not overall survival than luminal A subtype (P < 0.01); no significant difference was found on 5-year survival between basal-like and non-basal-like tumors when typed by basal-CK. CONCLUSION: Basal cell-like breast cancers are more likely to show more recurrence and worse outcome, but different immunohistochemical diagnostic criteria have an influence on their prognostic analysis, so a uniform diagnostic criteria is essential for the further study of basal-like breast cancers.

[Inflammatory pseudotumor-like follicular dendritic cell tumor of spleen].

OBJECTIVE: To study the clinicopathologic features of inflammatory pseudotumor-like follicular dendritic cell tumor of spleen. METHODS: One case of inflammatory pseudotumor-like follicular dendritic cell tumor of spleen was examined macroscopically and microscopically. Immunohistochemical study for CD21, CD23, CD35, clusterin, S-100 protein, vimentin, smooth muscle actin, CD1a, CD68, ALK protein, CD30, CD31, CD34, CD3 and CD20 was performed on formalin-fixed, paraffin-embedded sections by standard EnVision method. In-situ hybridization for Epstein-Barr virus (EBV)-encoded RNA was also carried out. RESULTS: Macroscopically, inflammatory pseudotumor-like follicular dendritic cell tumor was large in size, tan-colored, soft to rubbery in consistance and associated with central hemorrhage and necrosis. Histological examination showed scattered follicular dendritic cells admixed with abundant lymphocytes and plasma cells in the background, simulating inflammatory pseudotumor. On high-power magnification, the follicular dendritic cells possessed a moderate amount of pale to lightly eosinophilic cytoplasm, with indistinct cell borders. The nuclei were ovoid or spindly, with vesicular or stippled chromatin and small distinct, often centrally located, nucleoli. Some of the tumor cells showed nuclear pleomorphism and contained irregular foldings of nuclear membrane, coarse chromatin and prominent eosinophilic nucleoli. Mitotic figures were rarely identified. Immunohistochemical study showed that the tumor cells were positive for vimentin, clusterin, smooth muscle actin and CD68. They were weakly and focally positive for CD35 and S-100 protein, but negative for CD21, CD23, CD1a, ALK protein, CD30, CD31 and CD34. Most of the background lymphocytes were of T-lineage (CD3-positive) ,some were CD20 (B-cell marker)-positive. EBV RNA was demonstrated in the tumor cells by in-situ hybridization analysis. CONCLUSIONS: Inflammatory pseudotumor-like follicular dendritic cell tumor is a rarely encountered low-grade malignancy with distinctive morphologic pattern. It is associated with EBV infection.