Successful Crizotinib-targeted Therapy of Pediatric Unresectable ERC1::ALK Fusion Sarcoma.

Anaplastic lymphoma kinase ( ALK )-fusion sarcomas are rare part of the emerging theoretically targetable tyrosine kinase RAS::MAPK pathway fusion myopericytic-ovoid sarcomas. We report our clinicopathologic and treatment experience with an ALK fusion sarcoma. A novel ELKS/RAB6-interacting/CAST family member 1 - unaligned ALK fusion infiltrative nonmetastatic low-grade sarcoma of the right hand of a 15-month-old male was treated with crizotinib, an ALK tyrosine kinase inhibitor as oral monotherapy, inducing complete radiographic and clinical resolution by 10 months and sustained response now over 12 months after elective discontinuation. Crizotinib can successfully be used to treat unresectable novel ALK fusion sarcomas.

Cutaneous VCL::ALK fusion ovoid-spindle cell neoplasm.

Cutaneous VCL::ALK fusion spindle (ovoid) cell tumor is unique. Recently emerged RAS::MAP tyrosine kinase fusion sarcomas more commonly involve subcutis, skeletal muscle and even bone. We share our experience with a novel cutaneous VCL::ALK spindle cell tumor. An 11-year-old male presented with a back pedunculated pink-red papule thought to be a pyogenic granuloma. Biopsy histopathology revealed an epithelial collarette with pedunculated tumor extending to deep dermis/subcutis interface. The combination of spindled and epithelioid cells, an ovoid myopericytoid appearance within myxoid to collagenous stroma, low to moderate MIB1 and focal S100 protein without SOX10 immunostaining, were suggestive of a novel RAS::MAPK tyrosine kinase fusion sarcoma that is well described. ALK immunostain being positive, a next-generation sequencing comprehensive fusion panel was performed to reveal a VCL::ALK fusion. While epithelioid fibrous histiocytoma shares this fusion and similar dermal location and collarette pedunculation, this and other entities were excluded by older patient age, deeper dermal involvement, ovoid-to-spindled morphology, central pericytoid vasculature, myxoid stroma, moderate cellularity with low to moderate MIB1 expression, superficial ulceration, and focal S100 protein expression. Complete excision was performed with favorable follow-up to date. This novel VCL::ALK fusion spindle (ovoid) cell tumor of the dermis is best considered as part of the recently emerged RAS::MAP tyrosine kinase fusion sarcomas.

Intravascular fasciitis of the scalp as a complication of ICP monitor placement: a case report and review of the literature.

BACKGROUND/IMPORTANCE: There are only 56 documented cases of intravascular fasciitis, a rare variant of nodular fasciitis. Of these cases, only 2 involved the scalp. This lesion is amenable to surgical resection, making it important to differentiate it from soft tissue malignancies of the scalp. CLINICAL PRESENTATION: We report an unusual case of intravascular fasciitis involving the scalp at the site of an intracranial pressure (ICP) monitor of a 13-year-old male patient. The lesion was surgically excised with no recurrence upon 1-month follow-up. CONCLUSION: Intravascular fasciitis is a benign, reactive proliferation of soft tissue that may arise at sites of prior trauma. It appears as a soft, painless, mobile lesion, and immunohistochemical studies are required to differentiate it from malignant lesions. The standard of care is surgical resection of the lesion.

ALK rearrangements in infantile fibrosarcoma-like spindle cell tumours of soft tissue and kidney.

AIMS: Recurrent alterations in receptor tyrosine kinase (RTK) and downstream effectors are described in infantile fibrosarcoma (IFS)/cellular congenital mesoblastic nephroma (cCMN) and a subset of spindle cell sarcomas, provisionally designated 'NTRK-rearranged' spindle cell neoplasms. These two groups of tumours demonstrate overlapping morphologies and harbour alterations in NTRK1/2/3, RET, MET, ABL1, ROS1, RAF1 and BRAF, although their relationship is not fully elucidated. We describe herein a cohort of paediatric tumours with clinicopathological features not typical for inflammatory myofibroblastic tumour, but rather with similarities to cCMN/IFS harbouring ALK fusions. METHODS AND RESULTS: Clinicopathological features were assessed and partner agnostic targeted RNA sequencing on clinically validated platforms were performed. Tumours occurred in patients aged from 2 to 10 years (median age 2 years) with a 2:2 male to female ratio and an average size of 8.4 cm. Two tumours arose in soft tissues and two in the kidney. Morphological features included spindle to ovoid cells arranged in long fascicles or haphazardly within a myxoid to collagenised stroma; a subset of cases had either dilated, ectatic vessels or focal perivascular hyalinosis. By immunohistochemistry, all cases tested showed cytoplasmic expression of anaplastic lymphoma kinase (ALK) and one case demonstrated co-expression of CD34 and S100. CONCLUSIONS: This series of ALK-rearranged IFS-like tumours expands the spectrum of targetable kinases altered in these tumours and reinforces the potential overlap between IFS/cCMN-like tumours and the provisional entity of 'NTRK-rearranged' spindle cell neoplasms.

Animal model detects early pathologic changes of Charcot neuropathic arthropathy.

Charcot neuropathic arthropathy is a degenerative, debilitating disease that affects the foot and ankle in patients with diabetes and peripheral neuropathy, often resulting in destruction, amputation. Proposed etiologies include neurotraumatic, inflammatory, and neurovascular. There has been no previous animal model for Charcot. This study proposes a novel rodent model of induced neuropathic arthropathy to understand the earliest progressive pathologic changes of human Charcot. High-fat-diet-induced obese (DIO) Wild-type C57BL/6J mice (n = 8, diabetic) and age-matched low-fat-diet controls (n = 6) were run on an inclined high-intensity treadmill protocol four times per week for 7 weeks to induce mechanical neurotrauma to the hind-paw, creating Charcot neuropathic arthropathy. Sensory function and radiologic correlation were assessed; animals were sacrificed to evaluate hindpaw soft tissue and joint pathology. With this model, Charcot-DIO mice reveals early pathologic features of Charcot neuropathic arthropathy, a distinctive subchondral microfracture callus, perichondral/subchondral osseous hypertrophy/osteosclerosis, that precedes fragmentation/destruction observed in human surgical pathology specimens. There is intraneural vacuolar-myxoid change and arteriolosclerosis. The DIO mice demonstrated significant hot plate sensory neuropathy compared (P < 0.01), radiographic collapse of the longitudinal arch in DIO mice (P < 0.001), and diminished bone density in DIO, compared with normal controls. Despite exercise, high-fat-DIO mice increased body weight and percentage of body fat (P < 0.001). This murine model of diet-induced obesity and peripheral neuropathy, combined with repetitive mechanical trauma, simulates the earliest changes observed in human Charcot neuropathic arthropathy, of vasculopathic-neuropathic etiology. An understanding of early pathophysiology may assist early diagnosis and intervention and reduce patient morbidity and mortality in Charcot neuropathic arthropathy.

Novel fusion sarcomas including targetable NTRK and ALK.

BACKGROUND: Challenging emerging entities with distinctive molecular signatures may benefit from algorithms for diagnostic work-up. METHODS: Fusion sarcomas (2020-2021, during pandemic) were diagnosed by clinicoradiology, morphology, phenotype, and next-generation sequencing (NGS). RESULTS: Six fusion sarcomas in two males and four females involved the chest-wall, neck, or extremities; ages ranged 2-73, median 18 years. Sizes ranged 5.3-25.0, median 9.1 cm. These include high grade 1) TPR-NTRK1 of proximal femur with a larger rounded soft tissue mass, previously considered osteosarcoma yet without convincing tumor matrix. A pathologic fracture necessitated emergency hemipelvectomy (NED) and 2) novel KANK1-NTRK2 sarcoma of bone and soft tissue with spindled pleomorphic to epithelioid features (AWD metastases). 3) Novel ERC1-ALK unaligned fusion, a low grade infiltrative deep soft tissue hand sarcoma with prominent-vascularity, myopericytoid/lipofibromatosis-like ovoid cells, and collagenized stroma, was successfully treated with ALK-inhibitor (Crizotinib), avoiding amputation. These NTRK and ALK tumors variably express S100 and CD34 and were negative for SOX10. 4) and 5) CIC-DUX4 round cell tumors (rapid metastases/demise), one with COVID superinfection, were previously treated as Ewing sarcoma. These demonstrated mild pleomorphism and necrosis, variable myxoid change and CD99 reactivity, and a distinctive dot-like-Golgi WT1 immunostaining pattern. 6) A chest wall/thoracic round cell sarcoma, focal CD34/ keratins/CK7, revealed nuclear-STAT6, STAT6-NAB2 by NGS, confirming malignant solitary fibrous tumor, intermediate-risk-stratification (AWD metastases). CONCLUSIONS: Recent fusion sarcomas include new KANK1-NTRK2 and ERC1-ALK, the latter successfully treated by targeted-therapy. ALK/NTRK fusion partners TPR and KANK1 suggest unusual high-grade morphology/behavior. Clinicoradiologic, morphologic, and phenotypic algorithms can prompt molecular-targeted immunostains or NGS for final classification and promising inhibitor therapy.

Pathological response in children and adults with large unresected intermediate-grade or high-grade soft tissue sarcoma receiving preoperative chemoradiotherapy with or without pazopanib (ARST1321): a multicentre, randomised, open-label, phase 2 trial.

BACKGROUND: Outcomes for children and adults with advanced soft tissue sarcoma are poor with traditional therapy. We investigated whether the addition of pazopanib to preoperative chemoradiotherapy would improve pathological near complete response rate compared with chemoradiotherapy alone. METHODS: In this joint Children's Oncology Group and NRG Oncology multicentre, randomised, open-label, phase 2 trial, we enrolled eligible adults (aged ≥18 years) and children (aged between 2 and <18 years) from 57 hospitals in the USA and Canada with unresected, newly diagnosed trunk or extremity chemotherapy-sensitive soft tissue sarcoma, which were larger than 5 cm in diameter and of intermediate or high grade. Eligible patients had Lansky (if aged ≤16 years) or Karnofsky (if aged >16 years) performance status score of at least 70. Patients received ifosfamide (2·5 g/m2 per dose intravenously on days 1-3 with mesna) and doxorubicin (37·5 mg/m2 per dose intravenously on days 1-2) with 45 Gy preoperative radiotherapy, followed by surgical resection at week 13. Patients were randomly assigned (1:1) using a web-based system, in an unmasked manner, to receive oral pazopanib (if patients <18 years 350 mg/m2 once daily; if patients ≥18 years 600 mg once daily) or not (control group), with pazopanib not given immediately before or after surgery at week 13. The study projected 100 randomly assigned patients were needed to show an improvement in the number of participants with a 90% or higher pathological response at week 13 from 40% to 60%. Analysis was done per protocol. This study has completed accrual and is registered with ClinicalTrials.gov, NCT02180867. FINDINGS: Between July 7, 2014, and Oct 1, 2018, 81 eligible patients were enrolled and randomly assigned to the pazopanib group (n=42) or the control group (n=39). At the planned second interim analysis with 42 evaluable patients and a median follow-up of 0·8 years (IQR 0·3-1·6) in the pazopanib group and 1 year (0·3-1·6) in the control group, the number of patients with a 90% pathological response or higher was 14 (58%) of 24 patients in the pazopanib group and four (22%) of 18 patients in the control group, with a between-group difference in the number of 90% or higher pathological response of 36·1% (83·8% CI 16·5-55·8). On the basis of an interim analysis significance level of 0·081 (overall one-sided significance level of 0·20, power of 0·80, and O'Brien-Fleming-type cumulative error spending function), the 83·8% CI for response difference was between 16·5% and 55·8% and thus excluded 0. The improvement in pathological response rate with the addition of pazopanib crossed the predetermined boundary and enrolment was stopped. The most common grade 3-4 adverse events were leukopenia (16 [43%] of 37 patients), neutropenia (15 [41%]), and febrile neutropenia (15 [41%]) in the pazopanib group, and neutropenia (three [9%] of 35 patients) and febrile neutropenia (three [9%]) in the control group. 22 (59%) of 37 patients in the pazopanib group had a pazopanib-related serious adverse event. Paediatric and adult patients had a similar number of grade 3 and 4 toxicity. There were seven deaths (three in the pazopanib group and four in the control group), none of which were treatment related. INTERPRETATION: In this presumed first prospective trial of soft tissue sarcoma spanning nearly the entire age spectrum, adding pazopanib to neoadjuvant chemoradiotherapy improved the rate of pathological near complete response, suggesting that this is a highly active and feasible combination in children and adults with advanced soft tissue sarcoma. The comparison of survival outcomes requires longer follow-up. FUNDING: National Institutes of Health, St Baldrick's Foundation, Seattle Children's Foundation.

Novel FEMASK-score, a histopathologic assessment for destructive Charcot neuropathic arthropathy, reveals intraneural vasculopathy and correlates with progression and best treatment.

BACKGROUND: Charcot neuropathic arthropathy is a debilitating, rapidly destructive degenerative joint disease that occurs in diabetic, neuropathic midfoot. Clinicoradiologic assessment for Charcot neuropathic arthropathy previously relied on Eichenholtz stage. There is limited histopathologic data on this entity. We wanted to independently develop a histopathologic scoring system for Charcot neuropathic arthropathy. DESIGN: Retrieval of surgical pathology midfoot specimens from Charcot patients (2012-2019) were analyzed to evaluate joint soft tissue and bone. Considering progression from large (≥half 40× hpf) to small (

Scurvy: a rare case in an adult.

A 69-year-old man presented with unilateral calf pain, swelling, and erythematous rash. He was initially treated with antibiotics for suspected cellulitis. A venous duplex ultrasound, performed to exclude deep venous thrombosis, revealed multiple heterogeneous hypoechoic foci of unknown etiology throughout the calf musculature. His condition did not improve with antibiotics, instead progressing to a necrotic ulcer along the medial malleolus. Clinical suspicion of vascular insufficiency or vasculitis prompted an extensive imaging work-up. CT and MRI revealed the intramuscular abnormalities observed on previous ultrasound represented foci of intramuscular hemorrhage. Marrow signal abnormality was also noted in the proximal tibia. A punch biopsy of the skin rash ultimately demonstrated distorted hair follicles with perifollicular inflammation and hemorrhage concerning for scurvy. The diagnosis was confirmed by low vitamin C levels and dietary history. A resurgence of scurvy has occurred in the pediatric population in recent years. However, this diagnosis remains uncommon in adults, with limited reports of the potential advanced imaging findings in the current literature.

Extraneuraxial Hemangioblastoma: Clinicopathologic Features and Review of the Literature.

Extraneuraxial hemangioblastoma occurs in nervous paraneuraxial structures, somatic tissues, and visceral organs, as part of von Hippel-Lindau disease (VHLD) or in sporadic cases. The VHL gene plausibly plays a key role in the initiation and tumorigenesis of both central nervous system and extraneuraxial hemangioblastoma, therefore, the underlying molecular and genetic mechanisms of the tumor growth are initially reviewed. The clinical criteria for the diagnosis of VHLD are summarized, with emphasis on the distinction of sporadic hemangioblastoma from the form fruste of VHLD (eg, hemangioblastoma-only VHLD). The world literature on the topic of extraneuraxial hemangioblastomas has been comprehensively reviewed with ∼200 cases reported to date: up to 140 paraneuraxial, mostly of proximal spinal nerve roots, and 65 peripheral, 15 of soft tissue, 6 peripheral nerve, 5 bone, and 39 of internal viscera, including 26 renal and 13 nonrenal. A handful of possible yet uncertain cases from older literature are not included in this review. The clinicopathologic features of extraneuraxial hemangioblastoma are selectively presented by anatomic site of origin, and the differential diagnosis is emphasized in these subsets. Reference is made also to 10 of the authors' personal cases of extraneuraxial hemangioblastomas, which include 4 paraneuraxial and 6 peripheral (2 soft tissue hemangioblastoma and 4 renal).

Intracranial malignant peripheral nerve sheath tumor variant: an unusual neurovascular phenotype sarcoma case invading through the petrous bone.

INTRODUCTION: Intracranial malignant peripheral nerve sheath tumor (MPNST) is exceedingly rare. Previously reported cases of intracranial MPNST have been associated with development within a prominent cranial nerve. METHODS: This is the first report of an MPNST with both nerve sheath and vascular phenotype that follows the neurovascular bundle, without arising in a major cranial nerve or in the setting of neurofibromatosis type 1 (NF1). RESULTS: The patient is a 14-year-old boy with a history of worsening headaches for the past several months, left-sided hearing loss, nausea, vomiting, and vertigo. MRI was performed that demonstrated a large extra-axial tumor compressing the left infratemporal posterior temporal region. The tumor was associated with significant destruction of the superior portion of the petrous bone and extension through the petrous into the upper posterior fossa, immediately below the tentorium. The patient underwent surgical debulking and adjuvant chemotherapy with doxorubicin and ifosfamide. Pathology demonstrated a variant malignant peripheral nerve sheath tumor with both nerve sheath and vascular phenotype by immunostains. The patient's symptoms improved following treatment. CONCLUSION: We present the first reported case of an intracranial MPNST variant that developed along the neurovascular bundle as a sarcoma with both nerve sheath and vascular phenotype through the petrous bone and not associated with a major cranial nerve or with stigmata of neurofibromatosis type 1 (NF1). Although this is an extremely unusual presentation due to location and lack of prominent cranial nerves in that location, it is not unusual for benign nerve sheath tumors to follow the neurovascular bundle through foramen of cortical long bone or pelvis. This case suggests that physicians should incorporate intracranial MPNST variant into their differential diagnosis in the cranium, even when tumor is not located near a prominent cranial nerve. Surgical debulking and adjuvant chemotherapy with doxorubicin and ifosfamide has led to improvement in patient symptoms.

Unsuspected gastric glomus tumour.

Gastric glomus tumours (GGTs) are rare predominantly benign, mesenchymal neoplasms that commonly arise from the muscularis or submucosa of the gastric antrum and account for <1% of gastrointestinal soft-tissue tumours. Historically, GGT has been difficult to diagnose preoperatively due to the lack of unique clinical, endoscopic and CT features. We present a case of an incidentally identified GGT in an asymptomatic man that was initially considered a neuroendocrine tumour (NET) by preoperative fine-needle aspiration biopsy with focal synaptophysin reactivity. An elective robotic distal gastrectomy and regional lymphadenectomy were performed. Postoperative review by pathology confirmed the diagnosis of GGT. GGTs should be considered by morphology as a differential diagnosis of gastric NET on cytology biopsy, especially if there is focal synaptophysin reactivity. Additional staining for SMA and BRAF, if atypical/malignant, can help with this distinction. Providers should be aware of the biological behaviour and treatment of GGTs.

Establishment of a Neurodegenerative Charcot Mouse Model.

BACKGROUND: This study aimed to mimic the changes from Charcot neuropathic arthropathy in humans by examining the effects of exposing diet-induced obese (DIO) mice to neurotrauma through a regimented running protocol. METHODS: Forty-eight male wild-type C57BL/6J mice were obtained at age 6 weeks and separated into 2 groups for diet assignment. After a 1-week acclimation period, half of the mice consumed a high-fat diet (60% fat by kcal) ad libitum to facilitate neuropathic diet-induced obesity whereas the other half were control mice and consumed an age-matched standard low-fat control diet (10% fat by kcal). At age 12 weeks, half of the animals from each group were subjected to a high-intensity inclined treadmill running protocol, which has been previously demonstrated to induce neurotrauma. Sensory testing and radiographic analyses were periodically performed. Histopathologic analyses were performed post killing. RESULTS: DIO mice had significantly higher bodyweights, higher body fat percentages, and lower bone mineral density than wildtype control mice that were fed a normal diet throughout the experiment (P < .001 for each). DIO mice displayed significantly reduced sensory function in week 1 (P = .005) and this worsened over time, requiring 20.6% more force for paw withdrawal by week 10 (P < .001). DIO mice that ran demonstrated greater midfoot subluxation and tarsal instability over all time points compared with normal-diet mice that ran (P < .001). Histopathologic analyses revealed that DIO mice that ran demonstrated significant changes compared with controls that ran (P < .001 for each parameter). CONCLUSION: Changes akin to the earliest changes observed in or before joint destruction identified in diabetic Charcot neuropathic arthropathy in humans were observed. CLINICAL RELEVANCE: There is currently no standard of treatment for patients with Charcot neuropathic arthropathy. This study establishes a protocol for an animal model that can be used to study and compare interventions to treat this disease.

Outcomes After Preoperative Chemoradiation With or Without Pazopanib in Non-Rhabdomyosarcoma Soft Tissue Sarcoma: A Report From Children's Oncology Group and NRG Oncology.

Clinical trials frequently include multiple end points that mature at different times. The initial report, typically based on the primary end point, may be published when key planned co-primary or secondary analyses are not yet available. Clinical Trial Updates provide an opportunity to disseminate additional results from studies, published in JCO or elsewhere, for which the primary end point has already been reported.ARST1321 was a phase II study designed to compare the near complete pathologic response rate after preoperative chemoradiation with/without pazopanib in children and adults with intermediate-/high-risk chemotherapy-sensitive body wall/extremity non-Rhabdomyosarcoma Soft Tissue Sarcoma (ClinicalTrials.gov identifier: NCT02180867). Enrollment was stopped early following a predetermined interim analysis that found the rate of near complete pathologic response to be significantly greater with the addition of pazopanib. As a planned secondary aim of the study, the outcome data for this cohort were analyzed. Eight-five eligible patients were randomly assigned to receive (regimen A) or not receive (regimen B) pazopanib in combination with ifosfamide and doxorubicin + preoperative radiotherapy followed by primary resection at week 13 and then further chemotherapy at week 25. As of December 31, 2021, at a median survivor follow-up of 3.3 years (range, 0.1-5.8 years), the 3-year event-free survival for all patients in the intent-to-treat analysis was 52.5% (95% CI, 34.8 to 70.2) for regimen A and 50.6% (95% CI, 32 to 69.2) for regimen B (P = .8677, log-rank test); the 3-year overall survival was 75.7% (95% CI, 59.7 to 91.7) for regimen A and 65.4% (95% CI, 48.1 to 82.7) for regimen B (P = .1919, log-rank test). Although the rate of near complete pathologic response was significantly greater with the addition of pazopanib, outcomes were not statistically significantly different between the two regimens.

Structural changes in the collagen network of joint tissues in late stages of murine OA.

Osteoarthritis (OA) is the most prevalent degenerative joint disease, resulting in joint pain, impaired movement, and structural changes. As the ability of joint tissue to resist stress is mainly imparted by fibrillar collagens in the extracellular matrix, changes in the composition and structure of collagen fibers contribute to the pathological remodeling observed in OA joints that includes cartilage degeneration, subchondral bone (SCB) sclerosis, and meniscal damage. Using the established OA model of destabilization of the medial meniscus (DMM) in C57BL/6J mice, we performed a comprehensive analysis of the content and structure of collagen fibers in the articular cartilage, subchondral bone, and menisci using complementary techniques, which included second harmonic generation microscopy and immunofluorescence staining. We found that regions exposed to increased mechanical stress in OA mice, typically closest to the site of injury, had increased collagen fiber thickness, dysregulated fiber formation, and tissue specific changes in collagen I and II (Col I and Col II) expression. In cartilage, OA was associated with decreased Col II expression in all regions, and increased Col I expression in the anterior and posterior regions. Col I fiber thickness was increased in all regions with disorganization in the center region. In the superficial SCB, all regions exhibited increased Col I expression and fiber thickness in OA mice; no changes were detected in the deeper regions of the subchondral bone except for increased Col I fiber thickness. In the menisci, OA led to increased Col I and Col II expression in the vascular and avascular regions of the anterior meniscus with increased Col I fiber thickness in these regions. Similar changes were observed only in the vascular region of the posterior meniscus. Our findings provide, for the first time, comprehensive insights into the microarchitectural changes of extracellular matrix in OA and serve as guidelines for studies investigating therapies that target collagenous changes as means to impede the progression of osteoarthritis.

FUS (16p11) gene rearrangement as detected by fluorescence in-situ hybridization in cutaneous low-grade fibromyxoid sarcoma: a potential diagnostic tool.

Low-grade fibromyxoid sarcoma (LGFMS) is a rare, typically deep-seated soft tissue neoplasm with deceptively bland cytology and metastatic potential. A t(7;16)(q34;p11) translocation, yielding a FUS/CREB3L2 fusion gene, has been identified in approximately 80%-90% of deep soft tissue LGFMS. Cutaneous fibromyxoid neoplasms occur not infrequently; dermatopathologists rarely consider LGFMS in the differential diagnosis, as this lesion is uncommon in the skin. We identified a group of superficial LGFMS and a spectrum of other cutaneous fibromyxoid neoplasms and performed fluorescence in situ hybridization (FISH) to assess the frequency of FUS rearrangement. FISH for the chromosomal rearrangement of FUS (16p11), using a dual-color, break-apart probe (Abbott Molecular/Vysis, Des Plaines, IL), was performed on formalin-fixed paraffin-embedded tissue sections from superficial LGFMS (n = 6), myxomas (n = 10), and myxofibrosarcoma/myxoid malignant fibrous histiocytomas (myxoid MFH) (n = 5). One hundred nonoverlapping tumor nuclei per case were evaluated for either fused (normal) or split (translocated) signals. Of the LGFMS, 4 of 6 (67%) showed a rearrangement of FUS (range: 72%-80% positive nuclei per 100 nuclei). The other neoplasms within the differential diagnosis were devoid of any rearrangement involving FUS (range: 0%-2% positive nuclei per 100 nuclei). Our observed frequency of FUS rearrangement in superficial LGFMS is consistent with those published in the literature for more deeply seated lesions. When applied to suspicious superficial myxoid or fibromyxoid neoplasms, the FUS FISH probe in formalin-fixed paraffin-embedded tissue can be a useful ancillary technique for diagnosis of this uncommon and deceptively bland tumor.

Congenital epulis of the newborn: 10 new cases of a rare oral tumor.

Congenital epulis of the newborn (CEN) is a rare benign lesion that exclusively occurs in the oral and maxillofacial regions of newborns. The clinicopathologic features of CEN were examined and reviewed from the files of the Armed Forces Institute of Pathology from 1970 to 2000. Ten cases were included. Patient lesions were all present at birth but were surgically excised between 2 days and 6 weeks (median, 5.5 days). Nine lesions were in females; 1 case did not designate patient sex. Locations included 6 on the maxilla, 2 on the mandible, 1 on the designated maxillary lip, and 1 unknown. The cases included a patient with 2 lesions: 1 on mandibular and 1 on maxillary alveolar ridges, respectively. All other lesions were solitary and polypoid. Microscopically, these were pedunculated and nodular, composed of sheets to grouped clusters of medium-sized, ovoid-to-polygonal cells with abundant granular cytoplasm, distinct cell membranes, vascular-rich stroma, and attenuated overlying mucosa. Two cases also demonstrated spindled cells. The nuclei were vesicular and focally stippled, with distinct and slightly convoluted nuclear membranes; nucleoli were visible but not prominent. Mitotic activity was not observed. The vascular channels ranged from capillary-sized to venous, some staghorn-like with rare perivascular long-term inflammation. The venules exhibited a perivascular pericytic proliferation. Odontogenic epithelial rests were present in 2 cases. No cases demonstrated cytoplasmic hyaline globules. The lesional cells in all cases were negative for S-100 protein, CD68, CD34, CD31, keratins, desmin, calponin, and smooth muscle actin. Perivenular pericytes were positive for smooth muscle actin. Congenital epulis of the newborn is a rare oral entity with characteristic clinicopathologic features. It predominately affects girls, mainly on the maxillary alveolar ridge. It may be separated from "granular cell tumor" by location, patient age, absence of cytoplasmic hyaline globules, solid growth pattern, pericytic proliferation, attenuated overlying epithelium, and negativity for S-100 protein.

Primary malignant fibrous histiocytoma (myxofibrosarcoma/pleomorphic sarcoma not otherwise specified) of the breast: clinicopathologic study of 19 cases.

We present 19 cases of primary breast malignant fibrous histiocytoma (MFH) or myxofibrosarcoma/pleomorphic sarcoma not otherwise specified, the largest series to date, and compare our results with those in the literature to better define MFH in this anatomical location. Twenty-seven cases (MFH, myxofibrosarcoma, or pleomorphic sarcoma not otherwise specified) were reviewed using World Health Organization and French Federation of Cancer Centers criteria. Inclusion required location within breast parenchyma without extensive chest wall involvement. Morphological features were recorded, and immunohistochemistry was applied. Clinical data were extracted from patients' medical records. Clinically, there was 1 male patient. Of 15 patients with follow-up, 5 (33% overall) died of disease within an average of 7 months after diagnosis. Distant metastases and older patient age were associated with poor survival. Storiform-pleomorphic subtype was most common (10/19) with myxofibrosarcoma (6/19) and giant cell subtype (1/19) also observed. Unique lymphocyte-rich (1/19) and pleomorphic hyalinizing angiectatic tumor-like (1/19) morphologies are presented. Immunohistochemistry demonstrated expression of CD68 (71%), focal smooth muscle actin (36%), with rare focal estrogen and progesterone receptor immunoreactivity. All cases were negative for CD34, S-100 protein, desmin 33, and keratins, including CK7, CK20, CK5/6, and CK18. Malignant fibrous histiocytoma occurs as a primary lesion in breast parenchyma. Attention to morphological detail and immunohistochemistry avoids misdiagnosis. Entrapped breast ductal epithelium should not be misinterpreted as the epithelial component of a biphasic tumor. A florid lymphoid response should not be confused with metaplastic carcinoma. Pleomorphic hyalinizing angiectatic tumor-like features may be observed in MFH. Our study confirms the presence of MFH in breast and presents unique morphological observations of primary breast MFH.

Soft tissue Rosai-Dorfman disease: 29 new lesions in 18 patients, with detection of polyomavirus antigen in 3 abdominal cases.

Soft tissue Rosai-Dorfman disease (STRDD) is rare, previously reported only as single cases and few series. Simian virus 40 (SV40), a polyomavirus, has been identified in lymphoid processes and has a controversial role in neoplasia etiology. Occasional cytoplasmic pink granular inclusions and nuclear changes led us to explore a viral etiology. Only unpublished STRDD from our files with adequate material, soft tissue location, and diagnostic confirmation were included. Immunohistochemistry and follow-up were obtained. Eighteen STRDD patients, 4 male and 14 female, had 29 lesions; 5 with 2 or more lesions. Ages ranged from 8 to 81 years (mean 42.6 years and median 42.5 years). Soft tissue Rosai-Dorfman disease locations include trunk or proximal extremity (n = 19), distal extremity (n = 5), "abdominal" (n = 3), face (n = 1), and unknown subcutaneous site (n = 1). Sizes ranged from 0.5 to 13.7 cm (median, 2.4 cm). Previous disease included lymphoma, buttocks injection site, diabetes and hypothyroidism, and radiation for chronic dermopathy. No patients had a preceding or concurrent known viral infection; none had lymphadenopathy at present. None were known to be immunocompromised. Soft tissue Rosai-Dorfman disease was rapidly progressing. Initial pathologic diagnosis ranged from Rosai-Dorfman disease or inflammatory pseudotumor to inflammatory malignant fibrous histiocytoma. Grossly STRDDs were multilobulated, tan-yellow, and firm; morphologically, circumscribed, and subcutaneous-based. All had sheets of polygonal histiocytes with abundant pale eosinophilic cytoplasm, emperipolesis, plasma cells, and lymphocytes scattered and within clusters. Focal spindle cell change and mild pleomorphism were each observed in 3 patients; 2 had focal necrosis, none with mitoses. Small granular pink cytoplasmic inclusions and nuclear viral-like changes were observed. By immunohistochemistry, all STRDDs were positive for S100 protein, negative for CD1a, Epstein-Barr virus, and latent membrane protein, yet 3 (all abdominal, 1 multicentric) of the 9 studied were focally positive for cytoplasmic and nuclear SV40 polyomavirus. All were treated by local excision. Follow-up on 14 patients older than 8 to 16 years revealed recurrence in 3 patients with persistent multiple lesions, one with abdominal location. There were no metastases or death from disease. Soft tissue Rosai-Dorfman disease is a rapidly evolving, mostly solitary and nonrecurrent trunk and proximal extremity subcutaneous lesion in middle-aged females. More than one third can have persistent multicentric disease. It is important to recognize STRDD, to separate it from malignancy. Epstein-Barr virus/latent membrane protein was negative but polyomavirus was positive in 3 patients with abdominal STRDD, one with multicentric persistent disease. The relationship of polyomavirus to the evolution of abdominal STRDD should be further explored.