Plexiform Fibromyxoma in the Stomach: Immunohistochemical Profile and Comprehensive Genetic Characterization.

Plexiform fibromyxoma (PF), also referred to as plexiform angiomyxoid myofibroblast tumor, is an exceedingly rare mesenchymal neoplasm primarily affecting the stomach. Herein, we present a case of PF diagnosed in a 71-year-old male with a history of lung cancer, initially suspected to have a gastrointestinal stromal tumor (GIST) of the stomach, who subsequently underwent subtotal gastrectomy. The histopathological and molecular features of the tumor, including mutations in ABL1, CCND1, CSF1R, FGFR4, KDR, and MALAT1-GLI1 fusion, are elucidated and discussed in the context of diagnostic, prognostic, and therapeutic considerations.

A YAP1::TFE3 cutaneous low-grade fibromyxoid neoplasm: A novel entity!

Cutaneous fibromyxoid neoplasms (CFMN) comprise a vast category of benign and malignant tumors that include, but are not limited to, low-grade fibromyxoid sarcoma, myxofibrosarcoma, myxoid dermatofibrosarcoma protuberans, myxoid solitary fibrous tumor, and myxoid neurofibroma with differing implications for treatment and prognosis. Herein, a case of CFMN arising as a painless, slow-growing, flesh-colored forearm mass in a 53-year-old female is presented. The neoplasm comprised of copious myxoid material with banal spindle cells, exhibiting mild hyperchromasia, dissecting the dermal collagen table. Focal perivascular accentuation of spindle cells was identified in the absence of vasoformative features. Immunohistochemically, lesional cells were strongly and diffusely positive for CD34 and multifocally for Factor XIIIa and epithelial membrane antigen while negative for CD31, ERG, FLI-1, D2-40, smooth muscle actin, Desmin, S100, HMB-45, STAT6, MUC4, and keratins. RNA- and DNA-sequencing identified a YAP1::TFE3 fusion transcript that were subsequently corroborated by fluorescence in situ hybridization and immunohistochemistry for TFE3 (Xp11.23) locus rearrangement and strong, diffuse TFE3 immunoreactivity, respectively. To date, the YAP1::TFE3 fusion has only been identified in a subset of epithelioid hemangioendotheliomas and clear cell stromal tumors of the lung. This is the first report of a CFMN featuring a YAP1::TFE3 fusion (YAP1 Exon 1 and TFE3 Exon 4). The morphologic findings are unlike those previously described for epithelioid hemangioendothelioma and suggest that this neoplasm may represent a yet unclassified or novel CFMN entity. Although the patient is 1-year status postsurgical excision with no evidence of clinical recurrence, the clinical behavior of this novel entity remains to be fully characterized.

Prognostic value of CD34 expression status in patients with myxofibrosarcomas and undifferentiated pleomorphic sarcomas.

It is controversial whether patients with myxofibrosarcomas (MFSs) have better prognoses than those with undifferentiated pleomorphic sarcomas (UPSs). No useful prognostic factors have been established to date. We therefore aimed to evaluate the prognostic value of CD34 expression status in 192 patients with MFSs and UPSs. Using the log-rank test, we showed that patients with MFSs had a significantly better overall survival than did those with UPSs when defining the former as having a > 10% myxoid component (p = 0.03), but not when defining it as having a > 50% myxoid component (p = 0.1). Under the definition of MFSs as > 10% myxoid component, the log-rank test revealed that the diagnosis of the UPS and the CD34 loss (p < 0.001) were significant adverse predictors of overall survival. As per the Cox model, the CD34 loss remained an independent prognostic factor (hazard ratio = 3.327; 95% confidence interval 1.334-8.295), while the diagnosis of the UPS was a nonsignificant confounding factor (hazard ratio = 1.084; 95% confidence interval 0.679-1.727). In conclusion, CD34 expression status is a useful prognostic factor in patients with MFS and UPS, and it should be incorporated into grading systems that are used to predict outcomes.

The significance of enhancer of zeste homolog 2 (EZH2) expression in spindle cell lesions of the breast.

Spindle cell lesions of the breast are rare entities and pose a diagnostic challenge for pathologists due to overlapping morphologic and immunohistochemical features. We evaluated EZH2 expression in various benign (fibromatosis (n = 8), myofibroblastoma (n = 7), neurofibroma (n = 1), nodular fasciitis (n = 5), benign phyllodes tumor (n = 18)) and malignant (malignant phyllodes tumor (n = 8), metaplastic breast carcinoma (n = 16) and angiosarcoma (n = 8)) spindle cell lesions as a potential diagnostic and therapeutic marker. The EZH2 expression was evaluated semi-quantitatively to categorize the cases as 'low' and 'high' expression. All benign lesions showed low EZH2 expression, whereas high EZH2 expression was observed in the majority (28/32; 88%) of malignant lesions. The study results suggest that EZH2 may be used both as an additional diagnostic tool to reach an accurate diagnosis of the spindle cell lesions of the breast and as a therapeutic target for the malignant lesions.

Pleomorphic Fibroma: A Clinicopathologic Case Series With the Review of the Literature.

BACKGROUND: Pleomorphic fibromas are rare flesh-colored benign neoplasms first described in 1989. Their histopathology is notable for nuclear pleomorphism of spindle cells and multinucleate giant cells but lacking mitoses. The cellular origin of these tumors is unknown. This case series describes an additional 18 lesions with discussion of histopathology and immunohistochemistry. METHODS: This case series of 18 pleomorphic fibromas uses immunohistochemical staining for CD34, CD68, factor XIIIa, and S-100 and general histopathologic examination under light microscopy to describe the lesions. RESULTS: Immunohistochemical stains for CD34 showed nearly universal positivity of the pleomorphic spindle cells, although some more focally. The pleomorphic cells were negative for CD68, variably positive for factor XIIIa, and universally negative for S-100. All the lesions showed characteristic nuclear pleomorphism with absent mitoses. Collagen thickening was variable, mucin was absent, and perivascular inflammation was present in all lesions. CONCLUSIONS: Pleomorphic fibromas are fibrous lesions with benign clinical course and histopathologic findings including nuclear pleomorphism. Immunohistochemical staining characteristics of the lesion, along with unique spindle cells and multinucleate giant cells help to differentiate this from other tumors.

Primary pulmonary hyalinizing spindle cell tumor with giant rosettes: A clinicopathological and immunohistochemical study of 2 cases.

Two cases of primary intrapulmonary hyalinizing spindle cell tumor with giant rosettes are presented. The patients are one woman and one man ages 37 and 42 years respectively. Both patients presented with non-specific symptoms of cough, dyspnea, and chest pain. Imaging revealed the presence of an intrapulmonary mass. One tumor was located in the left lower lobe while the other tumor was in the right upper lobe. Both patients underwent lobectomy. The tumors ranged from 2.4 to 3.0 cm in greatest dimension and were characterized by the presence of a bland spindle cell proliferation with areas of hyalinization and the presence of the so-called giant rosettes. Immunohistochemical stains were performed and the spindle cell component show positive staining for vimentin and negative staining for Bcl-2, CD34, STAT6, p40. Keratin immunohistochemical stain highlighted the entrapped alveolar epithelium while S-100 protein showed weak focal staining in the spindle cells. Both patients have remained alive and well without evidence of recurrence or metastasis for a period of 6 to 14 months post-surgical resection. The cases herein presented highlight the ubiquitous distribution of this tumor and underscores the importance of keeping this particular tumor in the differential diagnosis of spindle cell tumors of the lung.

Acral fibromyxoma with loss of Rb1 by immunohistochemistry and fluorescence in situ hybridization: A diagnostically exploitable marker.

Acral fibromyxoma (AF) is a slow growing benign soft tissue tumor with predilection to subungal and periungal region of the hands or feet. CD34 is consistently expressed whereas very recently loss of Rb1 expression was described as a possible driver molecular event for this entity. Herein we present two additional cases of AF with loss of Rb1 expression by IHC and subsequent confirmation of loss of the RB1 gene locus by fluorescence in situ hybridization (FISH). We hope to raise awareness in dermatopathology community of this new discovery, which can be diagnostically exploitable for this distinct and probably underreported neoplasm.

Expression of connexin 43 by atypical fibroxanthoma.

INTRODUCTION: Connexins are transmembrane channel proteins that interconnect adjacent cells and allow the exchange of signaling molecules between cells and the extracellular milieu. They have been investigated in many tumors to obtain information about tumor nature, behavior, and prognosis. METHODS: Herein, we present a study on the immunohistochemical expression of connexin (Cx) 43 in 16 cases of atypical fibroxanthoma (AFX). For the immunohistochemical staining, a tissue array was obtained from the paraffin-embedded blocks. RESULTS: The expression was membranous and cytoplasmic in all cases. Thirteen cases (81.25%) showed strong staining. In the other three cases (18.75%), the staining was medium. None of the cases showed nuclear staining. Fifteen out of 16 cases showed a diffuse pattern, and only one case showed a focal pattern. CONCLUSIONS: Our results suggest that Cx43 may play an important role in the natural behavior of AFX.

Mitotically Active Cellular Fibroma of the Ovary Recurring After the Longest Interval of Time (16 yr): A Challenging Case With Systematic Literature Review.

Cellular fibromas represent ~10% of ovarian fibromas. Mitotically active cellular fibromas show mild nuclear atypia but ≥4 mitoses/10 high-power fields: the clinical course is usually uneventful but literature review is lacking. A 34-yr-old woman underwent left oophorectomy for a 9-cm ovarian mitotically active cellular fibroma at another hospital. The tumor was cellular (spindle cells in fascicular and storiform patterns) revealing mild atypia and 4 nonatypical mitoses/10 high-power fields without necrotic areas. After 16 yr, the tumor recurred as a 5-cm peritoneal nodule on the anterior sigmoid wall near the sigmoid-rectal junction. Frozen section revealed a spindle cell tumor invading the intestinal tunica muscularis propria: a gastrointestinal stromal tumor was favored as previous history was unavailable at that time. Intestinal resection was performed: no residual tumor was found. The patient was followed-up for 8 yr without further recurrences. The peritoneal nodule showed 2 mitoses/10 high-power fields and pericellular reticulin staining. The tumor was variably positive for vimentin/bcl-2/melan-A/CD56/ER/PR/α-inhibin/CD10/calretinin, focally positive for desmin, negative for pan-cytokeratin/actin/EMA/CD34/HMB45/CD117/CD99/S100/synaptophysin. The Ki67-index was ~9%. To our systematic literature review, 7 additional recurrent cases were reported. We describe a mitotically active cellular fibroma recurring after the longest interval of time. Extensive sampling of difficult cases should exclude malignant areas. Moderate nuclear atypia, tumor rupture, adhesions to pelvic/abdominal organs, infarction with extraovarian involvement, and incomplete excision may lead to relapse but there are conflicting data: prolonged follow-up can be suggested in these cases.

Nuclear ß-catenin immunoexpression in scars.

BACKGROUND: Histopathologically, scars can mimic superficial fibromatoses. Superficial fibromatoses are known to show nuclear ß-catenin immunoexpression, although the tumor types do not harbor CTNNB1 or APC alterations. This study aimed to evaluate nuclear ß-catenin immunoexpression in scars compared to that in superficial fibromatoses. METHODS: Immunostaining with an anti-ß-catenin antibody, clone 14, was performed on 8 superficial fibromatoses and 22 scars. The extent of ß-catenin nuclear staining was classified as negative (<10%), focally positive (10-49%), or diffusely positive (50-100%). ß-catenin staining intensity was semi-quantitatively graded as weak, moderate, or strong. RESULTS: In 21 (95%) scars, nuclear ß-catenin immunoexpression was detected in fibroblasts/myofibroblasts, with mainly diffuse (16/21) and moderate (14/21) to strong (5/21) staining. In contrast, seven (88%) of the eight superficial fibromatoses expressed ß-catenin in the nuclei of the lesional spindle cells, at varying levels of staining intensity. Fibroblasts in normal papillary dermis always showed nuclear ß-catenin expression to varying degrees but those in the reticular dermis did not. CONCLUSIONS: Scars typically exhibit nuclear ß-catenin expression similar to that in superficial fibromatoses. Thus, ß-catenin immunohistochemistry is not suitable for distinguishing superficial fibromatoses from scars.

SATB2 is frequently expressed in ossifying and non-ossifying peripheral oral fibroma of the gingival region but not in reactive fibromatous lesions from other intraoral sites.

Ossifying and non-ossifying peripheral oral fibromas (POF) of the gingival and alveolar mucosa are localized, cellular, small fibrous nodular lesions likely resulting from diverse external/ internal physical and chemical irritation or injuries. A central nidus of metaplastic woven bone characterizes and defines the ossifying variant. The inherent tendency of these lesions to ossify remains elusive. We herein analyze SATB2 expression as osteoblastic transcription and differentiation factor in 28 gingival POFs (10 of them ossifying) and compare them to 28 fibrous lesions from different non-gingival intraoral sites. Strong to moderate diffuse nuclear SATB2 immunoreactivity was detected in all ossifying (10/10; 100%) and in 8/18 (44%) non-ossifying gingival POFs, but in only 1/28 (3%) non-gingival oral reactive nodular fibrous lesions. This study illustrates for the first-time consistent expression of the osteoblastic marker SATB2 in ossifying and most of non-ossifying POFs of the gingival area but lack of this marker in reactive fibrous lesions from other oral cavity sites. This finding is in line with the proposed origin of gingival POFs from periodontal ligaments and may explain the frequent ossification observed in them. It is mandatory to consider this finding when assessing biopsies from SATB2-positive oral cavity neoplasms to avoid misinterpretation.

Cutaneous pleomorphic fibromas arising in patients with germline TP53 mutations.

Pleomorphic fibromas are rare benign cutaneous neoplasms associated with deletion/loss of chromosomes 13q and 17p, where RB1 and TP53 are located, respectively. Herein, we report five cases of pleomorphic fibroma arising in patients with germline TP53 mutations, suggesting a potential link with Li-Fraumeni syndrome. All three patients were female and young (mean age 27) with a strong personal and/or family oncologic history and confirmed pathogenic germline TP53 mutations. In two patients, multiple pleomorphic fibromas were diagnosed. Clinically, the lesions arose at various cutaneous sites and were small (≤2 cm) and raised (4/5). Histopathologically, the tumors were paucicellular, composed of atypical spindled to stellate cells with hyperchromatic and variably pleomorphic nuclei. Mitotic activity was exceedingly low, although rare atypical mitotic figures were seen in one case. Immunohistochemically, the tumor cells were diffusely positive for p16 (3/3) and showed loss of Rb expression (5/5). All cases showed aberrant p53 expression (overexpression in 4, complete loss in 1). The tumors have followed a benign clinical course with no evidence of progression or recurrence. In conclusion, the development of multiple pleomorphic fibromas in a young patient may be a clue to an underlying genetic cancer syndrome involving TP53.

Primary small intestine mesenteric low-grade fibromyxoid sarcoma with foci of atypical epithelioid whorls and diffuse DOG1 expression: a case report.

BACKGROUND: Low-grade fibromyxoid sarcoma (LGFMS) is a rare fibroblastic tumor often involving deep tissue of trunk and lower extremities in young to middle-aged patients. Rarely, LGFMS can occur in other sites including head and neck, chest, abdomen and female reproductive system. Three cases of LGFMS in mesentery of small intestine have been reported and all have conventional histologic features. Herein we reported a unique case of LGFMS in mesentery of small intestine. CASE PRESENTATION: A 43 year-old male with chief complaint of lower back pain for 4 years presented to our hospital. Physical exam reveal a firm, non-tender, non-distended, mobile large abdominal mass, which was shown on abdominal CT as a 10 cm retroperitoneal tumor. Biopsy revealed a spindle cell neoplasm in a myxoid background with a delicate vascular network. Tumor resection was performed. Gross examination of the resected specimen showed a 10.8 cm, tan-white, smooth, firm, lobulated mesenteric mass with bulging and gelatinous cut surface and confined within small bowel serosa. Microscopic examination demonstrated foci epithelioid cords and whorls with prominent atypia, in additional of regular, bland-appearing spindle cells in a fibrous and myxoid stroma and osseous metaplasia. The tumor cells stained diffusely positive for DOG1 with moderate staining density, and diffusely and strongly positive for MUC4. Rearrangement involving FUS (16p11.2) gene was identified with break-apart probe and confirmed by Anchored Multiplex PCR. A final diagnosis of low-grade fibromyxoid sarcoma was rendered. CONCLUSION: Our case highlights the importance of including LGFMS in the differential diagnosis of mesenteric tumors and the DOG1 positivity which could represent a potential diagnostic pitfall.

Expression of Neuroectodermal Markers in Atypical Fibromas in Two Dwarf Hamsters (Phodopus spp.).

A 2-year-old male Djungarian hamster (Phodopus sungorus) and a 1-year-old male Roborovski hamster (Phodopus roborovskii) were presented with expansile subcutaneous masses. The well-demarcated, firm, grey, multilobulated nodules displayed an homogeneous, white-grey cut surface. Histological examination revealed a neoplasm of variable cellularity consisting of spindle-shaped to polygonal 'ganglion cell-like' cells with abundant, amphophilic, vacuolated cytoplasm. Immunohistochemically, the tumour cells were labelled intensely for vimentin and nestin, moderately for neuron specific enolase and weakly for melan-A. The histological and immunohistochemical findings were suggestive of an atypical fibroma with evidence of a neuroectodermal phenotype.

Fine-needle aspiration features of ossifying fibromyxoid tumor in the breast: A case report and literature review.

Ossifying fibromyxoid tumor (OFT) is a very rare soft tissue tumor which is characterized by incomplete peripheral mature bone shell. To date, cytological features of OFT have been poorly studied with only seven case reports. In this study, an additional case of OFT investigated by fine-needle aspiration is presented. A 75-year-old man with advanced nasopharyngeal carcinoma presented with peripherally calcified right breast mass. Smears were hypercellular and stroma-rich. Tumor cells were mainly dispersed, with epithelioid morphology and eccentrically located nuclei. In the background, there was abundant eosinophilic myxoid secretion. No necrosis, atypia, or mitotic activity was found. The tumor showed diffuse S-100, CD10, STAT6 expression and focal desmin, estrogen receptor (ER), and progesteron receptor (PgR) expression. Fluorescence in situ hybridization study revealed PHF1 rearrangement in 9% of cells. Cytological characteristic of OFT is quite distinctive and precise diagnosis can be made, especially when it is coupled with compatible radiological findings.

Characterization of a novel CDC73 gene mutation in a hyperparathyrodism-jaw tumor patient affected by parathyroid carcinoma in the absence of somatic loss of heterozygosity.

Hyperparathyrodism-jaw tumor (HPT-JT) syndrome is an autosomal dominant disorder. Loss of function of the cell division cycle protein 73 homolog (CDC73) gene is responsible for the syndrome. This gene encodes an ubiquitously expressed 531 amino acid protein, parafibromin, that acts as a tumor suppressor. Loss of heterozygosity (LOH) of the CDC73 locus in many HPT-JT associated parathyroid tumors from patients with germline mutation is in accordance with Knudson's "two-hit" model for hereditary cancer. A 41-year-old man with mandible ossifying fibroma suffered from severe hypercalcemia due to parathyroid carcinoma (PC). Genetic analysis was performed to evaluate germinal and somatic CDC73 gene mutation as well as real-time qRT-PCR to quantify CDC73 mRNA, miR-155 and miR-664 expression levels. Immunohistochemistry and Western blotting (WB) assay were carried out to evaluate parafibromin protein expression. A novel heterozygous nonsense mutation, c.191-192 delT, was identified in the CDC73 gene. No CDC73 LOH was found in PC tissue, nor any differences in expression levels for CDC73 gene, miR-155 and miR-664 between PC and parathyroid adenoma control tissues. On the contrary, both immunohistochemistry and WB assay showed an approximate 90% reduction of parafibromin protein expression in PC. In conclusion, this study describes a novel germinal mutation, c.191-192 delT, in the CDC73 gene. Despite normal CDC73 gene expression, we found a significant decrease in parafibromin. We hypothesize that a gene silencing mechanism, possibly induced by microRNA, could play a role in determining somatic post-transcriptional inactivation of the wild type CDC73 allele.

Aberrant receptor tyrosine kinase signaling in lipofibromatosis: a clinicopathological and molecular genetic study of 20 cases.

Lipofibromatosis is a rare pediatric soft tissue tumor with predilection for the hands and feet. Previously considered to represent "infantile fibromatosis", lipofibromatosis has distinctive morphological features, with mature adipose tissue, short fascicles of bland fibroblastic cells, and lipoblast-like cells. Very little is known about the genetic underpinnings of lipofibromatosis. Prompted by our finding of the FN1-EGF gene fusion, previously shown to be a characteristic feature of calcifying aponeurotic fibroma (CAF), in a morphologically typical case of lipofibromatosis that recurred showing features of CAF, we studied a cohort of 20 cases of lipofibromatosis for this and other genetic events. The cohort was composed of 14 males and 6 females (median age 3 years; range 1 month-14 years). All primary tumors showed classical lipofibromatosis morphology. Follow-up disclosed three local recurrences, two of which contained calcifying aponeurotic fibroma-like nodular calcifications in addition to areas of classic lipofibromatosis, and no metastases. By FISH and RNA sequencing, four cases were positive for FN1-EGF and one case each showed an EGR1-GRIA1, TPR-ROS1, SPARC-PDGFRB, FN1-TGFA, EGFR-BRAF, VCL-RET, or HBEGF-RBM27 fusion. FN1-EGF was the only recurrent fusion, suggesting that some cases of "lipofibromatosis" may represent calcifying aponeurotic fibroma lacking hallmark calcifications. Several of the genes involved in fusions (BRAF, EGFR, PDGFRB, RET, and ROS1) encode receptor tyrosine kinases (RTK), or ligands to the RTK EGFR (EGF, HBEGF, TGFA), suggesting a shared deregulation of the PI3K-AKT-mTOR pathway in a large subset of lipofibromatosis cases.