Focal Myxoid Change Research Articles

Nodular Fasciitis of the Buccal Mucosa with a Novel USP6 Gene Rearrangement: A Case Report and Review of the Literature.

Nodular fasciitis is a rare but benign fibroblastic proliferation that typically presents as a solitary lesion with rapid growth and variable mitotic activity. The lesions usually occur on the extremities and occasionally in the head/neck region. Involvement of the buccal mucosa is extremely rare with only few reports in the literature; in this case report, we describe a 41 year old female who presented with a 6-month history of a stable intraoral lump at the junction of the upper and lower lip. Fine needle aspiration revealed an atypical spindle cell population with plump cells. The surgical excision demonstrated a well circumscribed tan-white firm nodule. Histologic examination revealed a spindle cell proliferation that grew in short, intersecting fascicles with focal storiform architecture. The lesion had a pushing border that was not overtly infiltrative and the stroma contained focal myxoid changes giving a "tissue culture" appearance to the cells. Immunohistochemical testing showed the tumor cells were vimentin (+), SMA (+), weakly Calponin (+), and desmin (-), cytokeratin (-), AE1/AE3 (-), S100 (-), ALK (-), STAT6 (-), and beta-catenin (-). Fluorescence in-situ hybridization (FISH) revealed a USP6 gene rearrangement with an atypical probe pattern. Next generation sequencing identified a novel SPTAN1::USP6 fusion gene confirming the diagnosis of buccal nodular fasciitis. Identification of the characteristic histologic features and USP6 gene rearrangements helped support the diagnosis. A review of the literature identified 25 cases of nodular fasciitis involving the buccal mucosa. The occurrence of this tumor in an unusual location may pose difficulties for diagnosis.

Primary extraskeletal osteosarcomas of the pleura: A clinicopathological, immunohistochemical, and molecular analysis of 4 cases

Four primary extraskeletal osteosarcomas of the pleura are presented. The patients were men between the ages of 63 and 78 years (average: 70.5 years) who presented with symptoms of chest pain, cough, and shortness of breath. Diagnostic imaging showed variably calcified, pleural-based masses and/or diffuse pleural thickening, clinically mimicking mesothelioma. Thoracoscopic surgical material was obtained for histopathological diagnosis. Histological findings showed the presence of a neoplastic spindle cell proliferation composed of fusiform cells with scant cytoplasm, elongated nuclei and inconspicuous nucleoli. Mitotic activity was easily identified. Additionally, all tumors showed extensive osseous differentiation in the form of osteoid matrix production; one tumor demonstrated additional chondrosarcomatous elements and another showed focal myxoid changes. Immunohistochemical analysis revealed that the tumor cells were uniformly negative for a wide variety of antibodies, including keratin AE1/AE3, keratin 5/6, D2-40, EMA, calretinin, WT-1, BerEP4, and HEG1; BAP1 was retained in all cases. In addition, fluorescence in situ hybridization for CDKN2A (p16) was negative for homozygous deletion in all tumors. Clinical follow-up showed that one patient had died 8 months after diagnosis and one had remained alive with short post-diagnostic follow-up. The tumors herein described highlight a challenging issue in the separation of mesothelioma with heterologous elements from true osteosarcomas of pleural origin. We propose that a diagnosis of extraskeletal osteosarcoma of the pleura is rendered for tumors with malignant osseous and/or cartilaginous differentiation in which comprehensive immunohistochemical studies and FISH analysis have failed to provide support for a diagnosis of mesothelioma with heterologous elements.

Morphological, immunohistochemical, and genetic analyses of epithelioid gastrointestinal stromal tumors

Epithelioid gastrointestinal stromal tumors (GISTs) are rare and may be confused with other tumors with epithelioid morphology. Therefore, herein, we collected 12 epithelioid GIST samples and summarized their morphological and immunohistochemical characteristics. Through genetic testing, we explored the correlation between morphology and gene mutations. The results showed that eight tumors showed focal or diffuse myxoid stromal changes with less cohesively arranged rhabdoid tumor cells; among these, five showed platelet-derived growth factor receptor alpha gene (PDGFRA) mutations. Signet ring cells with sclerosing stroma and receptor tyrosine kinase type III gene (KIT) mutations were present in two cases, which might be a KIT mutation-associated growth pattern in epithelioid GISTs. Succinate dehydrogenase gene (SDH) mutations were detected in three cases. Simultaneously, PDGFRA mutations were detected in two cases, and the Kirsten rat sarcoma viral oncogene homolog gene (KRAS) mutation was detected in another case. SDH-subunit B (SDHB) expression was partially weak and strongly diffuse in two cases with concurrent PDGFRA and SDHD mutations, respectively. The coexistence of PDGFRA and SDHD mutations may have affected SDHB expression. Altogether, we concluded that PDGFRA mutations may play an important role in co-mutant GIST pathogenesis.

Oxalate Nephropathy.

Oxalate Nephropathy.

Co-expression of ERG and CD31 in a subset of CIC-rearranged sarcoma: a potential diagnostic pitfall

AbstractCIC-rearranged sarcoma is characterized by round cell undifferentiated histology, frequent expression of ETV4 and WT1, and aggressive behavior. A clinical encounter of a case with CIC-DUX4 fusion and ERG/CD31 co-expression prompted us to systematically investigate ERG and CD31 expression status in 30 archival cases of CIC-rearranged sarcoma. Half (15) of them showed moderate or strong ERG expression in <5–100% of tumor cells, among which nine showed heterogeneous membranous CD31 reactivity, including four cases each showing diffuse or strong expression. None of them showed uniformly strong and diffuse ERG/CD31 co-expression; however, three cases were initially interpreted and treated as angiosarcoma without response. Except for smaller superficial tumor enrichment, the clinicopathological characteristics of these nine cases of ERG+/CD31+ CIC-rearranged sarcoma did not differ from those of remaining 21 cases. Five showed focal hemorrhagic clefts/cysts, mimicking vascular spaces. All tumors expressed ETV4 and/or nuclear WT1, and fusion to DUX4 was confirmed in seven cases. Four tumors examined by next-generation sequencing harbored no CIC missense mutations. Using DNA methylation profiling, one CD31+ CIC-rearranged sarcoma was clustered with CD31− CIC-rearranged sarcomas, but distant from angiosarcomas. When compared with epithelioid angiosarcomas lacking CIC rearrangements, ERG+/CD31+ CIC-rearranged sarcomas were distinguished by focal myxoid change and the entire lack of vasoformative architecture. The angiosarcomas were characterized by uniform strong expression of ERG and CD31, but none of them were found positive for ETV4 or nuclear WT1. Heterogeneous ERG/CD31 co-expression in a subset of CIC-rearranged sarcoma is a clinically relevant pitfall for angiosarcoma, as these two diseases are treated differently.

Lipoblastoma of the extremities

Lipoblastoma is a rare benign tumor of infancy and childhood, with similar radiographic imaging findings as malignant liposarcoma. Therefore, it is crucial to distinguish through other diagnostics and clinical features. We present our experience with the diagnosis and clinical management of this entity. A retrospective chart review was performed to identify children treated for lipoblastoma at our institution over a 30-year period. Charts were evaluated for diagnostic methods, treatment, and recurrence risk. A total of 9 males and 3 females were identified. The age at diagnosis ranged from 8 months to 44 years. Imaging modalities employed included ultrasound (N=5), MRI (N=12), X-ray (N=8), and CT (N=3). The tumor location was reported in the lower extremity (N=8) and upper extremity (N=4). The tumor size ranged from 1.7 to 18cm (mean=7.08cm). All patients underwent complete resection. Available pathology reports noted masses featuring mature adipocytes (N=1), fibrous septa (N=2), focal myxoid changes (N=1), and spindle cells (N=2). Nine patients underwent chromosomal analysis, which demonstrated five chromosome 8 abnormalities. No recurrences were reported. Three patients had follow-up imaging, and 11 had follow-up visits between 2 weeks to 15 years. Lipoblastoma is an uncommon childhood neoplasm of embryonic white fat that can also be present in adolescence and adulthood. Imaging, especially MRI, is helpful in limiting the differential diagnosis, but definitive diagnosis requires tissue biopsy, which should be obtained with core biopsy rather than fine needle aspiration. Surgical resection is curative with few complications. We do not recommend routine monitoring as recurrence is unlikely.

Unique Clinical and Pathologic Characteristics of Poorly Differentiated Primary Pleuro-Pulmonary Synovial Sarcoma

Primary pleuro-pulmonary synovial sarcoma is rare and poses a diagnostic challenge particularly when poorly differentiated. We present 15 cases of poorly differentiated primary pleuro-pulmonary synovial sarcoma and compare and contrast results with previously published series on usual better differentiated tumors. Clinical and radiologic findings were similar to usual pulmonary synovial sarcoma with typical imaging features. 7 of 10 patients with outcome data died of disease within 5 years. Histologically, tumors had densely cellular fascicles, hyalinized stroma, hemangiopericytoma-like vasculature, and focal myxoid change. Round cell and rare rhabdoid morphology were unique to poorly differentiated tumors. Immunohistochemistry demonstrated at least focal expression of pancytokeratin, EMA, CK7, CK5/6, calretinin, and CD56, and diffuse positivity with CD99 and bcl-2. Ten primary pulmonary synovial sarcomas with tissue available for study were positive for t(x;18), with a more even distribution of SS18/SSX1 and SS18/SSX2 tumors compared with better differentiated lung synovial sarcomas. In conclusion, our study confirms that clinical, histological, and immunohistochemical data from poorly differentiated primary pleuro-pulmonary synovial sarcoma is similar to better differentiated tumours but special caveats remain for accurate histopathologic diagnosis.

A Case of Giant Mediastinal Liposarcoma of Thymic Origin: A Rare Clinical Entity

Thymoliposarcoma is an exceedingly rare tumor of thymus with a very few cases reported till date. This case study presents a 45-year male with rare type of thymoma. On the contrast-enhanced CT images, there was a large mass lesion of predominantly fat attenuation in the pre-vascular compartment of the mediastinum insinuating on both sides of the visceral compartment of the mediastinum, and extending upto the bilateral cardio phrenic and anterior costophrenic angles, anterior to the right ventricle with loss of fat plane with the pericardium, with few sub-centimetric lymph nodes in the right paratracheal and AP window and a calcified right hilar lymph node, suggestive of well-differentiated liposarcoma/thymoliposarcoma. Initial CT guided tru-cut tissue biopsy was inconclusive, and the repeat biopsy revealed as fibro-collagenous tissue with area of necrosis, focal myxoid changes in the background with presence of cells which are spindle to oval in shape with mild nuclear pleomorphism and negative for S100, Cytokeratin, CD34, desmin. The entire tumor was resected en masse after meticulous dissection without the support of cardiopulmonary bypass (CPB) with an intact pericardium. Final histopathology report of the surgical biopsy specimens is consistent with dedifferentiated thymoliposarcoma with focal ganglionic cell differentiation. Postoperative follow-up CECT of thorax revealed no evidence of residual mass in the pre-vascular compartment. The patient is disease-free and asymptomatic after 6-month and he is under routine follow-up under Radiotherapy department since he received 30 Gy of postoperative radiotherapy (PORT).

Lipomas of the Oral Cavity: Utility of MDM2 and CDK4 in Avoiding Overdiagnosis as Atypical Lipomatous Tumor.

Traumatized lipomas with degenerative change may demonstrate histopathologic features that mimic atypical lipomatous tumor (ALT). Previously reported series of ALT involving the oral cavity preceded routine use of MDM2 and CDK4 immunohistochemistry. Our aim is to evaluate MDM2 and CDK4 immunohistochemical expression in adipocytic tumors arising in this site, in conjunction with the histiocytic marker PU.1, to determine whether MDM2 and CDK4 impacts classification. 17 cases originally diagnosed as ALT were retrieved and immunohistochemical studies for MDM2, CDK4 and PU.1 were performed. FISH analysis for MDM2 amplification was performed in select cases. For this study group, the male:female ratio was 9:8 and the median age was 62 (range 41-88). All 17 cases presented as well- or predominantly well-circumscribed proliferations of variably sized, mature adipocytes exhibiting uni- or multi-vacuolation with occasional scalloped nuclei and mild nuclear atypia. Variable amounts of fibrous stroma with focal myxoid change and bland spindle cells were identified in 14/17 cases. Lipoblasts or atypical hyperchromatic stromal cells were not identified in any cases. 14 of 17 cases were negative for MDM2 and CDK4 in tumor cells and 11 of these 14 showed weak nuclear positivity for MDM2 in histiocytes. 3 of 17 cases showed weak, multifocal immunohistochemical expression of MDM2 and CDK4. PU.1 highlighted histiocytes in all 17 cases. FISH analysis for MDM2 amplification was negative in all 3 cases with weak MDM2/CDK4 expression. All cases were reclassified as lipoma with degenerative changes. ALT, in all likelihood, is less common than previously thought in this anatomic location and best diagnosed with ancillary studies. MDM2 expression in histiocytes is best interpreted in conjunction with CDK4 immunohistochemistry and confirmatory FISH for MDM2 amplification.

TGFBR3 and MGEA5 rearrangements are much more common in “hybrid” hemosiderotic fibrolipomatous tumor-myxoinflammatory fibroblastic sarcomas than in classical myxoinflammatory fibroblastic sarcomas: a morphological and fluorescence in situ hybridization study

Myxoinflammatory fibroblastic sarcoma (MIFS) is a rare low-grade sarcoma that most often involves the distal extremities of adults. Some MIFSs have been reported to show TGFBR3 and MGEA5 rearrangements. TGFBR3 and MGEA5 rearrangements have also been reported in hemosiderotic fibrolipomatous tumor (HFLT), in pleomorphic hyalinizing angiectatic tumor (PHAT), and in rare tumors allegedly showing features of both HFLT and MIFS (hybrid HFLT-MIFS). These findings have led to speculation that HFLT, MIFS, PHAT, and hybrid HFLT-MIFS are closely related; however, areas resembling HFLTs are only very rarely encountered in previous series of MIFSs. We studied classic examples of these tumors with the goal of clarifying the relationship between MIFS and HFLT-MIFS. Cases of MIFS (n=31), hybrid HFLT-MIFS (n=8), PHAT (n=2), HFLT (n=1), and undifferentiated pleomorphic sarcoma (n=4) were retrieved from our archives, and the diagnoses were verified by 5 soft tissue pathologists. Using previously validated break-apart fluorescence in situ hybridization probes, we analyzed for TGFBR3 and MGEA5 rearrangements. Only 2 of 31 MIFSs harbored MGEA5 rearrangements; all lacked TGFBR3 rearrangements. Six of 8 hybrid HFLT-MIFSs harbored rearrangements of TGFBR3 and/or MGEA5. Both PHATs were positive for rearrangements of TGFBR3 and/or MGEA5. The HFLT was positive for rearrangements of both TGFBR3 and MGEA5. All undifferentiated pleomorphic sarcomas with focal myxoid change were negative. We conclude that (1) TGFBR3 and/or MGEA5 rearrangements are much more common in hybrid HFLT-MIFSs than in classic MIFSs, (2) HFLTs and MIFSs may be unrelated lesions, and (3) hybrid HFLT-MIFSs most likely represent HFLTs with sarcomatous progression, rather than tumors strictly related to classic MIFSs.

Extremely rare case of vulvar myxoid epithelioid sarcoma.

Epithelioid sarcoma is a distinct sarcoma type with specific morphology and immunophenotype. An epithelioid sarcoma of the vulva is an extremely rare and aggressive tumor and most commonly occurs on the labia majora in women of reproductive age. Only few cases have been reported, especially with the presence of focal myxoid changes. Early diagnosis is difficult because of its benign appearance as a painless subcutaneous nodule. Optimal treatment is not well established due to its rarity. We report a successfully approached case of vulvar epithelioid sarcoma that occurred in a 34-year-old female patient, treated with wide local excision, and review of the current medical literature.

A Giant, Deep, Benign Fibrous Histiocytoma with a Palisading Pattern.

Dear Editor: A 42-year-old male patient presented to our clinic with a skin-colored mass that had been present for 2 years; his medical and family histories were otherwise unremarkable. Physical examination revealed a soft, movable, skin-colored mass on his upper left back, with a brown, bean-sized pedunculated nodule on the overlying skin (Fig. 1A). Excisional biopsy was performed. The tumor, which was well demarcated and localized in the subcutaneous layer, measured 5.4×5.1×2.1 cm (Fig. 1B). The histopathological examination indicated that the lesion was an encapsulated mass, located in subcutaneous tissue with a central cavity. The tumor was well-circumscribed by a fibrous capsule, and no honeycomb pattern was observed in the marginal area. In the tumor periphery, large blood vessels with a dilated, branching appearance were observed (Fig. 2A). The tumor cells were arranged in a palisading and partially storiform pattern, with focal myxoid change (Fig. 2B). Under high magnification, the tumor cells were spindle shaped with elongated nuclei and an ill-defined cytoplasm; individual cells were infiltrating between collagen bundles and arranged in a palisading pattern, similar to Verocay bodies (Fig. 2C). Cellular atypia and mitotic bodies were not detected. Immunohistochemical analysis revealed that the cells were strongly positive for CD34 (Fig. 2D); focally positive for factor XIIIa; and negative for S-100 (Fig. 2E), desmin, actin, and CD68. A diagnosis of giant, deep, benign fibrous histiocytoma (BFH), with a palisading pattern, was rendered, with no evidence of recurrence at 15 months after excision. Fig. 1 (A) A skin-colored mass on the back (arrows) with a coincident overlying skin tag (inset: close-up view). (B) The excised 5×5×2 cm well-encapsulated erythematous oval mass. Fig. 2 (A) Scanning view of the histopathological examination of the lesion showing an encapsulated mass located from the lower dermis through the subcutaneous tissue with a central cavity. The tumor was well circumscribed by a fibrous capsule, and no honeycomb ... BFH, which is characterized by several histological subtypes, is among the most-common soft tissue skin tumors. Since Fletcher's1 description in 1990 of 21 cases of deep BFH (DBFH), several more cases have been reported1,2,3. DBFH, which accounts for <1%~2% of all BFH cases, is larger and arises lower in the subcutis1, and confers an increased risk of local recurrence and distant metastasis3. Similar to BFH, giant fibrous histiocytoma (>5 cm), which represents a rare variant of fibrous histiocytoma, is benign, and no local recurrence after surgical excision has been reported to date4. Palisading BFH is a rare variant of BFH, first described by Schwob and Santa Cruz5 in 1986. On histopathological examination, palisading BFH resembles a schwannoma; the lack of neural cells and S-100 negativity could facilitate the differential diagnosis5. Although several cases of palisading BFH have been reported2,5, only one case of palisading DBFH has been documented2. In our patient, the tumor cells were strongly positive for CD34; therefore, it is difficult to exclude dermatofibrosarcoma protuberance. However, Gleason and Fletcher3 reported that 40% of DBFH cases are positive for CD34. The histopathological findings of a well-circumscribed capsule, low cell density, and a lack of atypical cells and mitotic bodies also suggest a benign nature; therefore, the final diagnosis was an uncommon case of giant DBFH.

Desmoplastic Fibroblastoma Presenting as a Parotid Tumour: A Case Report and Review of the Literature

Desmoplastic fibroblastomas (DFs) are rare fibrous soft tissue tumours that usually arise in subcutaneous tissue or skeletal muscle in a variety of anatomical sites. These lesions most frequently present as painless, slow-growing mobile masses. A case of DF is described in a 47-year-old man who presented with a painless right parotid mass of 2months duration. At surgery, the lesion was attached to the tail of the right parotid gland. Histopathological examination demonstrated a fibrous lesion comprising spindled and stellate shaped fibroblasts with focal myxoid stromal change. The features were consistent with a DF. This report documents a rare parotid lesion which may mimic other more common parotid gland neoplasms.

Intraosseous ganglion cyst within the L4 lamina causing spinal stenosis

There are rare reports of intraosseous ganglion cysts in the cervical spine. However, to our knowledge, there are no previous reports of these cysts occurring in the lumbar spine. To report a case of symptomatic lumbar spinal stenosis caused by an intraosseous ganglion cyst of the L4 lamina that communicated with the spinal canal. Case report. An 86-year-old woman was referred to our spine service for a 2-year history of anterior thigh and leg pain. Magnetic resonance imaging revealed a benign-appearing intraosseous cyst in the left L4 lamina communicating with a posterior epidural cyst at L4-L5 causing marked spinal stenosis. The patient was treated successfully with a laminectomy and resection. The patient underwent partial laminectomies of L4 and L5 preserving the interspinous ligaments between L5-S1 and L3-L4. The cyst was removed en bloc without violation of the cyst wall. Histopathologic examination revealed focal myxoid changes without a cellular lining of the cyst wall, confirming the diagnosis of intraosseous ganglion cyst. This is the first report to describe an intraosseous ganglion cyst occurring in the lumbar spine. Although spinal stenosis is commonly a result of degenerative joint or disc disease, it occasionally may result from more obscure causes. This case illustrates a patient with an intraosseous ganglion cyst within the spinal lamina resulting in spinal stenosis, treated successfully with a laminectomy and resection.

Myxoid epithelioid sarcoma: a diagnostic challenge. A report on six cases

Epithelioid sarcoma (ES) is a distinct sarcoma-type with a specific morphology and immunophenotype. Whereas focal myxoid change does occur, to our knowledge only two cases of ES with diffuse myxoid stroma have been reported previously. To characterize more clearly the myxoid variant of ES, we describe six additional cases and discuss the differential diagnoses. Cases were retrieved from the authors' files and studied histologically, immunohistochemically and by molecular methods. The age of the patients, four females and two males, ranged from 16 to 74 years (median: 33 years). The neoplasms arose in an extremity (two cases), the abdominal wall, groin, perineum and shoulder (one case each). Histologically, four cases were of the conventional type, and two were of the proximal type and the immunophenotype was typical for ES. The tumour stroma, however, revealed prominent myxoid changes, ranging from 50 to 90% (median: 75%). Only one of the proximal type ES showed a SMARCB1 mutation, whereas the other tumours showed no mutation. The myxoid variant of ES represents a diagnostic challenge and may be confused with other benign and malignant myxoid neoplasms. The main differential diagnosis is myoepithelioma of the skin and soft tissue.

Adrenocortical Tumors With Myxoid Features: A Distinct Morphologic and Phenotypical Variant Exhibiting Malignant Behavior

Myxoid changes have been rarely reported both in adrenocortical adenomas and carcinomas. The recent observation by our group of an adrenal myxoid tumor with morphologically borderline features, but aggressive clinical behavior prompted us to review a series of 196 adrenocortical lesions, comprising 122 carcinomas and 74 adenomas, to define the morphologic, phenotypical and clinical characteristics of adrenocortical tumors with myxoid features. Fourteen cases, including 12 carcinomas and 2 borderline tumors, formed the basis of this report, and were characterized by a variably abundant myxoid component (from 5% to 90% of tumor) and 2 distinct cellular growth patterns: the first (10 cases), mostly associated with a predominant myxoid stromal component, was made of small cells with mild atypia arranged in cords and microcysts; the second (4 cases) was characterized by focal myxoid changes in tumors otherwise similar to conventional adrenocortical carcinoma, with large atypical cells having an eosinophilic cytoplasm and a diffuse or nodular architecture. The above mentioned patterns were absent in all adenomas reviewed. A peculiar reactivity to neurofilaments was seen, mostly associated to the presence of predominant rather that focal myxoid stromal changes, and in 40% of conventional adrenocortical carcinomas, thus representing an undescribed potential pitfall in the differential diagnosis of adrenal lesions. Myxoid adrenocortical tumors probably represent a rare but histologically and phenotipically distinct entity and, although rare cases of benign lesions are on record, they seem to be generally associated to morphologic and clinical features of malignancy.

Well-differentiated spindle cell liposarcoma (‘atypical spindle cell lipomatous tumor‘) does not belong to the spectrum of atypical lipomatous tumor but has a close relationship to spindle cell lipoma: clinicopathologic, immunohistochemical, and molecular analysis of six cases

Well-differentiated spindle cell liposarcoma represents a rare atypical/low-grade malignant lipogenic neoplasm that has been regarded as a variant of atypical lipomatous tumor. However, well-differentiated spindle cell liposarcoma tends to occur in subcutaneous tissue of the extremities, the trunk, and the head and neck region, contains slightly atypical spindled tumor cells often staining positively for CD34, and lacks an amplification of MDM2 and/or CDK4 in most of the cases analyzed. We studied a series of well-differentiated spindle cell liposarcomas arising in two female and four male patients (age of the patients ranged from 59 to 85 years). The neoplasms arose on the shoulder, the chest wall, the thigh, the lower leg, the back of the hand, and in paratesticular location. The size of the neoplasms ranged from 1.5 to 10 cm (mean: 6.0 cm). All neoplasms were completely excised. The neoplasms were confined to the subcutis in three cases, and in three cases, an infiltration of skeletal muscle was seen. Histologically, the variably cellular neoplasms were composed of atypical lipogenic cells showing variations in size and shape, and spindled tumor cells with slightly enlarged, often hyperchromatic nuclei. Multivacuolated lipoblasts were present in three neoplasms. Focal myxoid stromal changes were seen in three cases. Immunohistochemically, CD34 was at least focally positive in all cases, whereas scattered tumor cells only showed a nuclear expression of MDM2 in two neoplasms. FISH analysis revealed a deletion of the Rb-1 gene in all six cases, whereas no MDM2/CDK4 amplification was identified in all cases tested. Follow-up information was available in four cases (range from 4 to 24 months), and revealed a local recurrence in one case. Although well-differentiated spindle cell liposarcoma and atypical lipomatous tumor behave clinically similar, it can be speculated on the basis of clinicopathologic and molecular findings that well-differentiated spindle cell liposarcoma may constitute an independent entity rather than a morphologic variant of atypical lipomatous tumor, and may represent the atypical/low-grade counterpart of spindle cell lipoma.

Palisaded Encapsulated (“Solitary Circumscribed”) Neuroma of the Oral Cavity: A Review of 55 Cases

We describe the clinicopathologic characteristics of 55 oral palisaded encapsulated (solitary circumscribed) neuromas (PEN/SCN). Fifty-five cases of PEN/SCN in 54 patients were reviewed. Lesions were categorized according to their histologic pattern, partial or complete encapsulation, presence of Verocay bodies and presence of a parent peripheral nerve. In 13 selected cases immunohistochemical evaluation for neuronal markers (S-100, GFAP, NFP, EMA) was performed. When immunoreaction with EMA was weak, claudin-1 and glut-1 stains were utilized. Thirty-eight patients were men and 16 were women. Mean patient age was 48 years (SD: +/-14). The vast majority involved the masticatory (palate and gingiva) mucosa (76.4%) followed by the labial mucosa, the tongue and buccal mucosa. Recurrence was recorded in only one case. Histologically, 34 lesions had a lobular pattern, 10 were plexiform, 7 fungating and 4 multilobular. Stroma was limited, but focal myxoid changes were seen at the periphery of the lobules. Only one predominantly myxoid lesion was encountered. The number of intralesional axons varied, but the ratio of Schwann cells to axons was generally less than 1:2. Most lesions (89%) were only partially surrounded by perineurium. Tumor cells were S-100 positive and GFAP negative. The parent nerve was identified in 50% of the cases. Overlying epithelium was generally atrophic. Peritumoral connective tissue was generally unremarkable, but chronic inflammation was present in five cases. PEN/SCN is a relatively common peripheral nerve sheath tumor. Generally, its diagnosis is simple. GFAP may be of help to distinguish PEN/SCN from other peripheral nerve sheath tumors (schwannoma, neurofibroma, traumatic neuroma) in cases where histomorphologic features may be confusing. Finally, pathologists should be aware of the occurrence of plexiform and multilobular PEN/SCN variants, to avoid misinterpretation as plexiform neurofibroma or schwannoma.

Myxoid Epithelioid Sarcoma: Clinicopathologic Analysis of 2 Cases

In the nearly 4 decades since its original delineation as a distinct clinicopathologic entity, several morphologic variations of epithelioid sarcoma have been described. Proximal, angiomatoid, and fibroma-like variants have been reported, as have cases displaying significant hyalinization, calcification, and/or ossification. Furthermore, it has long been recognized that epithelioid sarcoma may display focal myxoid change. Herein, the authors describe 2 examples of epithelioid sarcoma that displayed diffuse myxoid change. Both cases were otherwise typical, both morphologically and immunophenotypically, of epithelioid sarcoma. The tumors in both cases were localized, and the patients were treated with wide local excision followed by adjuvant radiotherapy. The patients are free of disease recurrence after 25 and 37 months of follow-up. Differential considerations that may arise because of the composite of morphologic and immunophenotypic findings noted in these cases are discussed, especially if encountered in a small biopsy. These cases further expand the morphologic spectrum of epithelioid sarcoma.

Unusual Multifocal Glomeruloid Pattern in a Well-Differentiated Papillary Mesothelioma of the Peritoneum

by clefted spaces. The mesothelial origin of the tumor was confirmed by immunoreactivity showing positive immunolabeling for calretinin (1:300; Dako, Carpinteria, California), CK 5/6 (1:30; Bio Sb, Santa Barbara, California), thrombomodulin (1:50; Dako), WT-1 (1:50; Cell Marque, Austin, Texas), and CK7 (1:100; Cell Marque). CK20 (1:50; Cell Marque) was negative (Figure 2). Well-differentiated papillary mesothelioma is an uncommon distinct subtype of mesothelioma that occurs principally in the peritoneum of women in the third and fourth decades. It is often discovered incidentally during abdominal or pelvic surgery, and it is generally regarded as a tumor of low malignant potential. In the English literature, less than 100 cases have been reported affecting both men and women, including cases arising in the pleura and tunica vaginalis. Histologically, WDPM is A46-year-old woman presented to the ABC Medical Center in Mexico City with the clinical picture of acute cholecystitis and underwent cholecystectomy. The patient had no history with regard of asbestos exposure. During surgery, incidental multifocal small firm, white to tan peritoneal nodules were found, ranging from 5 mm to 1 cm, and on frozen section, a diagnosis of papillary epithelial neoplasm consistent with well-differentiated papillary mesothelioma (WDPM) was rendered (Figure 1A). The patient underwent total hysterectomy, along with omentectomy and resection of multiple peritoneal and diaphragmatic implants. The serosal membranes of the uterus and ovary were unremarkable, although a microscopic focus (1 mm) of parenchymal infiltration was found in the left ovary. The histological study disclosed a well-developed tubulopapillary growth pattern with solid areas. The papillae were lined by a single layer of uniform cuboidal to flattened cells with minimal cytological atypia, covering thin fibrovascular cores. Mitosis was absent. The stroma showed focal myxoid change. Focal psammoma bodies were present. Throughout the tumor, constituting approximately 20% of the neoplasm and mainly localized to the periphery of the nodules, the fibrovascular papillae were arranged forming a distinct glomeruloid pattern of growth characterized by round to oval neoplastic mesothelial cell tufts supported by a fibrovascular core (Figures 1B and 1C). The mesothelial cells were sometimes arranged in semicircular concentric rows separated