Pseudosarcomas of soft tissue

Animal models of tendon calcification: Past, present, and future

Tendon calcification is a common clinical condition that frequently occurs as a complication after tendon injury and surgery, or as an expression of fibrodysplasia ossificans progressiva. This condition can be referred to by various names in clinical practice and literature, including tendon ossification, tendon mineralization, heterotopic ossification, and calcific tendonitis. The exact pathogenesis of tendon calcification remains uncertain, but current mainstream research suggests that calcification is mostly cell mediated. To further elucidate the pathogenesis of tendon calcification and to better simulate the overall process, selecting appropriate experimental animal models is important. Numerous animal models have been utilized in various clinical studies, each with its own set of advantages and limitations. In this review, we have discussed the advancements made in research on animal models of tendon calcification, with a focus on the selection of experimental animals, the sites of injury in these models, and the methods employed for modeling.

"Bone in the penis" or fasciitis ossificans of the penis - a first time description of a pseudo-tumor at an extraordinary site

BACKGROUND

Fasciitis ossificans is a rare subtype of nodular fasciitis, a benign soft tissue tumor with reactive characteristics. Due to its rapid growth, it is often misdiagnosed as a malignant tumor. While fasciitis ossificans commonly originates from the subcutaneous tissue and can appear throughout the body, it may also arise from extraordinary sites.

CASE PRESENTATION

We report the first-ever documented case of fasciitis ossificans arising from the penis in a male patient who presented with a tumor on the glans penis. The tumor was surgically resected due to suspicion of penile cancer. Initial histopathological analysis led to a misdiagnosis of squamous cell carcinoma. However, pathological consultation ultimately confirmed the diagnosis of fasciitis ossificans of the penis originating from the glans penis by demonstrating ossification.

CONCLUSION

This case underscores the importance of considering fasciitis ossificans in the differential diagnosis of soft tissue tumors, even in unusual locations such as penile soft tissue.

Fibro-Osseus Pseudotumor of the Digit: A Case Report and Review of Literature

Introduction

Bony subungual growths arising on the digital tip are uncommon. Among these, subungual exostosis is a common cause.

Case Presentation

We describe a 35-year-old-male patient with a rare occurrence of a fibro-osseus pseudotumor of the digit. It presents with reactive intramembranous ossification, with no continuity with the distal phalanx, helping differentiate it from a subungual exostosis. The patient presented with an asymptomatic subungual growth, lifting up the nail plate distally causing onycholysis. The characteristic clinical, radiological, and histopathological features of the case are described, which helped confirm the diagnosis.

Conclusion

Cases with fibro-osseus pseudotumor of the digit reported in literature are reviewed comprehensively. The factors helping differentiate this from the other bony tumors affecting the distal phalanx, including subungual exostosis, myositis ossificans, and osteosarcoma are also highlighted.

Fibroblastic and Myofibroblastic Soft-Tissue Tumors: Imaging Spectrum and Radiologic-Pathologic Correlation

Fibroblastic and myofibroblastic tumors are a variable group of neoplasms ranging from benign to malignant. These lesions may affect patients of any age group but are more frequently encountered in the pediatric population. Patient clinical presentation depends on the location, growth pattern, adjacent soft-tissue involvement, and pathologic behavior of these neoplasms. In the 2020 update to the World Health Organization (WHO) classification system, these tumors are classified on the basis of their distinct biologic behavior, histomorphologic characteristics, and molecular profiles into four tumor categories: (a) benign (eg, fibrous hamartoma of infancy, nodular fasciitis, proliferative fasciitis, fibroma of the tendon sheath, calcifying aponeurotic fibroma); (b) intermediate, locally aggressive (eg, desmoid fibromatosis); (c) intermediate, rarely metastasizing (eg, dermatofibrosarcoma protuberans, myxoinflammatory fibroblastic sarcoma, low-grade myofibroblastic sarcoma, infantile fibrosarcoma); and (d) malignant (eg, sclerosing epithelioid fibrosarcomas; low-grade fibromyxoid sarcoma; myxofibrosarcoma; fibrosarcoma, not otherwise specified). Detection of various components of solid tumors at imaging can help in prediction of the presence of corresponding histopathologic variations, thus influencing diagnosis, prognosis, and treatment planning. For example, lesions with a greater myxoid matrix or necrotic components tend to show higher signal intensity on T2-weighted MR images, whereas lesions with hypercellularity and dense internal collagen content display low signal intensity. In addition, understanding the radiologic-pathologic correlation of soft-tissue tumors can help to increase the accuracy of percutaneous biopsy and allow unnecessary interventions to be avoided. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Intraneural Nodular Fasciitis of the Dorsal Scapular Nerve: Case Report and Review of the Literature

BACKGROUND

 Nodular fasciitis is a benign neoplasm occurring predominantly in the subcutaneous tissue. There have been nine intraneural occurrences described in the literature.

CASE REPORT

 A 37-year-old woman presented with numbness and tenderness in her left shoulder and scapula and a slightly dropped left shoulder, without history of trauma. A magnetic resonance imaging (MRI) of the cervical spine showed a well-circumscribed oval mass deep to the levator scapula muscle. Due to persisting symptoms and an unknown nature of the process, surgical excision was performed, and histopathologic analysis confirmed diagnosis of a benign fibroblastic/myofibroblastic neoplasm, nodular fasciitis. The postoperative course was uneventful and the patient was without symptoms at 4 months of follow-up.

METHODS

 We reviewed the available literature (PubMed, Google Scholar), with nine published cases of intraneural nodular fasciitis. The reported clinical, radiologic, and histopathologic parameters were evaluated and compared.

DISCUSSION

 Most of the cases reported in the literature were symptomatic, with tenderness and palpability being the main symptoms. Six of the reported cases occurred in the forearm, whereas three were in the leg. To the best of our knowledge, ours is the first reported case of nodular fasciitis occurring in the trunk. Ours is the only case to display desmin positivity, which supports the reactive hypothesis of nodular fasciitis.

CONCLUSION

 Intraneural nodular fasciitis is an extremely rare diagnosis. Due to its benign natural course, a multidisciplinary approach with this extremely rare diagnosis in mind is needed to avoid overtreatment.

Multimodality imaging features of USP6-associated neoplasms

Since the discovery of USP6 gene rearrangements in aneurysmal bone cysts nearly 20 years ago, we have come to recognize that there is a family of USP6-driven mesenchymal neoplasms with overlapping clinical, morphologic, and imaging features. This family of neoplasms now includes myositis ossificans, aneurysmal bone cyst, nodular fasciitis, fibroma of tendon sheath, fibro-osseous pseudotumor of digits, and their associated variants. While generally benign and in many cases self-limiting, these lesions may undergo rapid growth, and be confused with malignant bone and soft tissue lesions, both clinically and on imaging. The purpose of this article is to review the imaging characteristics of the spectrum of USP6-driven neoplasms, highlight key features that allow distinction from malignant bone or soft tissue lesions, and discuss the role of imaging and molecular analysis in diagnosis.

A case report of an unusual temporomandibular joint mass: Nodular fasciitis

Nodular fasciitis (NF) is a benign myofibroblastic proliferation that grows very rapidly, mimicking a sarcoma on imaging. It is treated by local excision, and recurrence has been reported in only a few cases, even when excised incompletely. The most prevalent diagnoses of temporomandibular joint (TMJ) masses include synovial chondromatosis, pigmented villonodular synovitis, and sarcomas. Cases of NF in the TMJ are extremely rare, and only 3 cases have been reported to date. Due to its destructive features and rarity, NF has often been misdiagnosed as a more aggressive lesion, which could expose patients to unnecessary and invasive treatment approaches beyond repair. This report presents a case of NF in the TMJ, focusing on various imaging features, along with a literature review aiming to determine the hallmark features of NF in the TMJ and highlight the diagnostic challenges.

Non-traumatic myositis ossificans circumscripta in the anterior abdominal wall of a seven-year-old Ugandan child: A case report

Myositis ossificans circumscripta (MOC) is a benign and self-limiting heterotopic ossification in the subcutaneous fat, tendons, muscles, and nerves. It is commonly due to trauma and is frequently encountered in the arm, shoulder, thigh, and hand which are prone to trauma. Non-traumatic MOC arising from the abdominal muscles is extremely rare. We report a case of 7-year-old male child with a three-year history of progressive painless abdominal swelling in the left hypochondria region with no history of associated trauma. CT scan of the abdomen showed a well-defined hyperdense mass in the left external oblique muscle. Histological diagnosis confirmed myositis ossificans of the external oblique muscle. The mass was removed surgically with no immediate or late complications.

Rare Pseudosarcomatous Lesions Posing Diagnostic Challenges: Histopathologic Examination as a Dominant Tool Preventing Misdiagnosis of Proliferative Fasciitis

Proliferative fasciitis is an extremely rare benign myofibroblastic proliferation that typically presents as a rapidly growing subcutaneous mass. Precise histopathological interpretation is required to obtain a proper diagnosis. Due to a symptomatology overlap, discrimination from soft tissue sarcomas is crucial in the prevention of unnecessary excessive treatment that could be potentially harmful to the patients. Here, we present a rare case of atypical localization of proliferative fasciitis. The lesion was predominantly localized in the groin with the invasion of the scrotum and clinically mimicked soft tissue sarcoma. However, according to a proper histopathologic analysis, the diagnosis of proliferative fasciitis was concluded. With a large number of pseudosarcomatous lesions, there is a rising urge to introduce these rare but benign processes to physicians in order to prevent misdiagnosing patients.

Neuron-to-vessel signaling is a required feature of aberrant stem cell commitment after soft tissue trauma

The functional interdependence of nerves and blood vessels is a well-established concept during tissue morphogenesis, yet the role of neurovascular coupling in proper and aberrant tissue repair is an emerging field of interest. Here, we sought to define the regulatory relationship of peripheral nerves on vasculature in a severe extremity trauma model in mice, which results in aberrant cell fate and heterotopic ossification (HO). First, a high spatial degree of neurovascular congruency was observed to exist within extremity injury associated heterotopic ossification. Vascular and perivascular cells demonstrate characteristic responses to injury, as assessed by single cell RNA sequencing. This vascular response to injury was blunted in neurectomized mice, including a decrease in endothelial proliferation and type H vessel formation, and a downregulation of key transcriptional networks associated with angiogenesis. Independent mechanisms to chemically or genetically inhibit axonal ingrowth led to similar deficits in HO site angiogenesis, a reduction in type H vessels, and heterotopic bone formation. Finally, a combination of single cell transcriptomic approaches within the dorsal root ganglia identified key neural-derived angiogenic paracrine factors that may mediate neuron-to-vascular signaling in HO. These data provide further understanding of nerve-to-vessel crosstalk in traumatized soft tissues, which may reflect a key determinant of mesenchymal progenitor cell fate after injury.

Cranial Fasciitis in Children: Expanding the Spectrum of USP6-Associated Clonal Transient Neoplasms

Background: Cranial fasciitis (CF) is a benign (myo)fibroblastic proliferation of children. Typical presentation consists of a rapidly growing solitary mass on the temporal or parietal cranium in the first 2 years of age. CF is characterized by a rapid growth followed by a relative slowdown and even growth arrest. The finding of somatic USP6 gene rearrangements demonstrating clonality in CF together with its clinical behavior places it in the category of diseases recently termed "transient neoplasia."Methods: Histological, immunohistochemical, and molecular findings of 18 patients with CF were retrospectively studied.Results: The tumor typically presented as a painless rapidly enlarging mass in the temporal region. Sixty-six percent of the cases harbored USP6 gene rearrangement. Nine patients were treated with gross total resection (GTR) and 9 with subtotal tumor resection (STR). Two patients treated with GTR had recurrence. Five patients treated with STR had progression-free disease for at least 10 months after surgery and in four patients the tumor regressed spontaneously a median 16 months after surgery.Conclusions: In this largest series to date, we reported the clinicopathological, immunohistochemical, and molecular findings of 18 pediatric cases of CF with emphasis on the clinical growth pattern of these tumors.

NGF-TrkA signaling dictates neural ingrowth and aberrant osteochondral differentiation after soft tissue trauma

Pain is a central feature of soft tissue trauma, which under certain contexts, results in aberrant osteochondral differentiation of tissue-specific stem cells. Here, the role of sensory nerve fibers in this abnormal cell fate decision is investigated using a severe extremity injury model in mice. Soft tissue trauma results in NGF (Nerve growth factor) expression, particularly within perivascular cell types. Consequently, NGF-responsive axonal invasion occurs which precedes osteocartilaginous differentiation. Surgical denervation impedes axonal ingrowth, with significant delays in cartilage and bone formation. Likewise, either deletion of Ngf or two complementary methods to inhibit its receptor TrkA (Tropomyosin receptor kinase A) lead to similar delays in axonal invasion and osteochondral differentiation. Mechanistically, single-cell sequencing suggests a shift from TGFβ to FGF signaling activation among pre-chondrogenic cells after denervation. Finally, analysis of human pathologic specimens and databases confirms the relevance of NGF-TrkA signaling in human disease. In sum, NGF-mediated TrkA-expressing axonal ingrowth drives abnormal osteochondral differentiation after soft tissue trauma. NGF-TrkA signaling inhibition may have dual therapeutic use in soft tissue trauma, both as an analgesic and negative regulator of aberrant stem cell differentiation.

Nodular fasciitis: a comprehensive, time-correlated investigation of 17 cases

The self-limited nature of nodular fasciitis (NF) is well-known but its precise mechanism has not yet been clarified. We observed that "young" NF (preoperative duration <1 month) consistently contains a higher percentage (~80%) of USP6 break-apart FISH signals than "old" NF (preoperative duration >3 months) (~20%). Thus, we hypothesized that our original observation may reflect a connection with the self-limited nature of NF. Seventeen cases with reliable data concerning the onset were selected, thus approximating the lifetime of each tumor. Besides the USP6 interphase FISH examination, we also checked the most common MYH9-USP6 fusion using RT-PCR. Because of the known pathways of the tumorigenesis of NF, the mRNA level of USP6, TRAIL, IFN-beta, JAK1, STAT1, STAT3, JUN, and CDKN2A was measured using qRT-PCR. Regarding proteins, USP6, p16, p27, TRAIL, and IFN-beta were examined using immunohistochemistry. Targeted gene panel next-generation sequencing (NGS) of three cases was additionally performed. We found a strong negative correlation (p = 0.000) between the lifetime and percentage of USP6 break-apart signals and a strong positive relationship (p = 0.000) between USP6 break-apart signals and mitotic counts. Results of immunostainings, along with qRT-PCR results, favored the previously-suggested USP6-induced negative feedback mechanism through activation of TRAIL and IFN-beta, likely resulting in apoptosis and senescence of tumor cells harboring USP6 fusions. Targeted-NGS resulted in the detection of several variants, but no additional recurrent changes in the pathogenesis of these tumors. We revealed on a cellular level the USP6-induced negative feedback mechanism. In conclusion, we emphasize that in "old" NF, the percentage of USP6 break-apart FISH signals can be as low as 14-27% which can be very important from a differential diagnostic point of view. We emphasize that a careful examination and interpretation of the NGS data is needed before clinical decision-making on treatment.

Benign infiltrative myofibroblastic neoplasms of childhood with USP6 gene rearrangement

AIMS

Several morphologically overlapping (myo)fibroblastic neoplasms harbour USP6 fusions, including aneurysmal bone cysts, nodular fasciitis, myositis ossificans, cranial fasciitis, fibro-osseous pseudotumour of the digits, and cellular fibroma of the tendon sheath. USP6-induced neoplasms are almost universally benign and cured by local excision. We aim to highlight the diagnostic value of USP6 fusion detection in a series of aggressive-appearing paediatric myofibroblastic tumours.

METHODS AND RESULTS

Three deep-seated, radiographically aggressive, and rapidly growing childhood myofibroblastic neoplasms were morphologically and molecularly characterised by USP6 break-apart fluorescence in-situ hybridisation (FISH), transcriptome sequencing, and targeted capture analysis. Each tumour occurred in the lower-extremity deep soft tissue of a child presenting with pain, limping, or a mass. In all three patients, imaging studies showed a solid mass that infiltrated into surrounding skeletal muscle or involved/eroded underlying bone. The biopsied tumours consisted of variably cellular myofibroblastic proliferations with variable mitotic activity that lacked overt malignant cytological features. FISH showed that all tumours had USP6 rearrangements. On the basis of these results, all three patients were treated with conservative excision with positive margins. The excised tumours had foci resembling nodular fasciitis, fibromatosis, and pseudosarcomatous proliferation. Next-generation sequencing revealed COL1A1-USP6 fusions in two tumours and a COL3A1-USP6 fusion in the third tumour. One tumour had a subclonal somatic APC in-frame deletion. No recurrence was observed during follow-up (8-40 months).

CONCLUSION

We present a series of benign, but aggressive-appearing, USP6-rearranged myofibroblastic tumours. These deep-seated tumours had concerning clinical and radiographic presentations and did not fit into one distinct histological category. These cases highlight the diagnostic value of USP6 fusion detection to identify benign nondescript tumours of this group, especially those with aggressive features, to avoid overtreatment.

A benign, low-grade myofibroblastic lesion mimicking a sarcoma

Benign myofibroblastic lesions can clinically and histologically be mistaken for sarcoma. Excessive and potentially disfiguring surgical treatment can be avoided by ruling out malignancy. We present the case of a low-grade, myofibroblastic lesion of the lip, which shows how detailed clinical examination rather than reliance on histopathological information alone helped to achieve this. Differential diagnoses of myofibroblastic lesions are also discussed.

Primary Sarcomas of the Larynx: A Single Institutional Experience with Ten Cases

Sarcomas infrequently arise in the larynx where the vast majority of tumors are of epithelial origin. Given their rarity, studies of these lesions are limited in number. In this series, we describe our institutional experience with ten primary sarcomas of the larynx encountered over an 18 year period, comprising 1.9% of all laryngeal malignancies observed in this timeframe. The cases include four chondrosarcomas and one example each of osteosarcoma, embryonal rhabdomyosarcoma, undifferentiated spindle cell sarcoma, well-differentiated liposarcoma, Kaposi sarcoma, and synovial sarcoma. Patients included nine males and one female, with a mean age of 59 years (range 34-75). The mean clinical follow-up time was 3.4 years (range 0-12 years). Clinically, all patients presented with vocal and/or respiratory symptoms, and all received surgical treatment with the exception of the case of Kaposi sarcoma. Of the nine patients who underwent surgical excision, two, both chondrosarcomas, experienced local recurrence. No instances of distant metastasis or death of disease had occurred at the time of preparation of this manuscript. In conclusion, primary sarcomas of the larynx are rare but tend to present with early symptoms. This likely allows for earlier detection and intervention as compared to their counterparts in other deep soft tissue locations. Pathologically, it is important, although difficult in some cases, to distinguish these neoplasms from sarcomatoid carcinoma and reactive processes. Careful morphologic and immunohistochemical evaluation, as well as correlation with the clinical and radiologic findings, is important for accurate tumor classification.

Ossifying fasciitis at an extraordinary site - a case report and analysis of diagnostic pitfalls

Ossifying fasciitis is a very rare disease of reactive character; however, it can mimic malignant lesions, especially osteosarcoma. We report a case of a 30-year-old woman, who experienced a rapidly growing painful lesion of the left knee joint, preceded by a trauma. The tumor was resected, and the histopathological image suggested a malignant lesion with features of an osteosarcoma. A detailed correlation with a clinicopathological and radiological analysis led to the final diagnosis of ossifying fasciitis at an extraordinary site of patellar retinaculum. Our case shows that the close similarity between ossifying fasciitis and osteosarcoma may be challenging.

Heterotopic Ossification: A Comprehensive Review

Heterotopic ossification (HO) is a diverse pathologic process, defined as the formation of extraskeletal bone in muscle and soft tissues. HO can be conceptualized as a tissue repair process gone awry and is a common complication of trauma and surgery. This comprehensive review seeks to synthesize the clinical, pathoetiologic, and basic biologic features of HO, including nongenetic and genetic forms. First, the clinical features, radiographic appearance, histopathologic diagnosis, and current methods of treatment are discussed. Next, current concepts regarding the mechanistic bases for HO are discussed, including the putative cell types responsible for HO formation, the inflammatory milieu and other prerequisite “niche” factors for HO initiation and propagation, and currently available animal models for the study of HO of this common and potentially devastating condition. © 2019 The Authors. JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.

A case of multiple osseous choristomas arising on the medial side of the lateral pterygoid muscle

Osseous choristoma is a rare entity in the oral and maxillofacial region. The most common site is the tongue, followed by the buccal mucosa. Osseous choristoma of the muscle is unusual and few cases have been described in the literature. No reports have described osseous choristoma arising on the medial side of the lateral pterygoid muscle. Herein, we report the first such case. A 61-year-old woman was referred to our facility for treatment of temporomandibular joint disorder. Computed tomography (CT) revealed two osseous lesions on the medial side of the lateral pterygoid muscle. Preoperatively, a three-dimensional (3D) life-sized model of the skull was fabricated from the CT imaging data. The 3D skull model was used to clarify the 3D positional relationships of the osseous lesions relative to the surrounding anatomical structures. Surgery to remove the osseous lesions was performed under general anesthesia. Unfortunately, only the larger of the two masses was able to be resected because of the risk of nerve and vascular injury. Histological examination revealed that the resected lesion comprised mature lamellar bone with regular osteocytes and no atypia. The diagnosis was multiple osseous choristomas based on the histological and clinical findings.

Calcific myonecrosis: diagnostic dilemma

Calcific myonecrosis is a rare benign condition affecting mainly the muscles of a single leg compartment. It is thought to follow a history of trauma with a latent period of years. Patients present with a slowly growing mass. Differential diagnosis from a malignant tumour can be made from the history and the distinctive radiographical features of a fusiform lesion with predominantly peripheral calcifications. Magnetic resonance imaging may be necessary to confirm the diagnosis; treatment is largely symptomatic.

USP6 activation in nodular fasciitis by promoter-swapping gene fusions

Nodular fasciitis is a self-limited myofibroblastic lesion that can be misdiagnosed as a sarcoma as a result of its rapid growth, cellularity, and sometimes prominent mitotic activity. A recurrent translocation t(17;22) has been identified in nodular fasciitis, fusing the coding region of USP6 to the promoter region of MYH9, and resulting in increased USP6 expression. A subset of cases show USP6 rearrangement without the typical fusion variants by RT-PCR, or any MYH9 rearrangement by FISH. We sought to further characterize such tumors using molecular diagnostic assays. A novel RT-PCR assay was designed to detect the two known MYH9-USP6 fusion types in formalin-fixed paraffin-embedded and frozen tissue, and a break-apart FISH assay was designed to detect USP6 rearrangement. Twenty-six cases of nodular fasciitis diagnosed between 2002 and 2013 were retrieved from the pathology files of our institutions and were confirmed to be positive by FISH and/or RT-PCR. Seven samples showed USP6 rearrangement by FISH but were negative for MYH9-USP6 fusion by RT-PCR; these cases were subjected to a next-generation sequencing assay utilizing anchored multiplex PCR technology. This assay targets a single partner gene associated with fusions in bone and soft tissue tumors for agnostic detection of gene fusion partners. Novel fusion partners were identified in all seven cases and confirmed by RT-PCR. Structurally, all fusions consisted of the juxtaposition of the entire coding region of USP6 with the promoter of the partner gene, driving increased USP6 expression. This study confirms the neoplastic nature of nodular fasciitis, defines additional pathogenic fusion partners, and adds to the growing body of literature on USP6-associated neoplasia. Given the diagnostic challenges of these tumors, molecular assays can be useful ancillary tools; however, the prevalence of promoter swapping must be recognized when interpreting results.

Florid reactive periostitis of the long bone: A case series of seven patients

BACKGROUND

Florid reactive periostitis (FRP) is a rare benign periosteal lesion, which mostly involves the tubular bones of the extremities. FRP of the long bone is especially rare. We here report a case series of long bone FRP and also discuss the differential diagnosis and clinical outcome of our series.

PATIENTS AND METHODS

In total, four female and three male patients with long bone FRP and a mean age of 25.1 years were evaluated for this study, from which four upper extremity and three lower extremity FRP lesions were identified. Patients were classified according to the clinical, radiological and pathological manifestations of the lesion.

RESULTS

Periosteal reaction and edema around the lesions were observed in all cases. Calcified mass, bone marrow edema and cortical erosion were observed in six out of seven patients. Moreover, two lesions with peripheral mineralization and zoning appearances were observed. Limb rest and anti-inflammatory therapy proved to be sufficient treatment in all cases. The lesions were spontaneously resolved in all cases, leaving a residual exostosis.

CONCLUSION

Our report indicates that short bone and long bone FRP could reveal different characteristics in some aspects, including the choice of the therapeutic approach. In spite of the favorable clinical outcome of long bone FRP, its differentiation from more aggressive lesions, especially osteosarcoma and osteomyelitis, should still be taken into consideration. In addition, according to our evidence, the implication of the zonal pattern in differential diagnosis of FRP and myositis ossificans (MO) could be re-evaluated.

Intraocular inflammatory mass associated with lens-induced uveitis

Intraocular inflammatory tumefactions large enough to simulate neoplasms are uncommon. We report a patient with a large intraocular inflammatory mass composed of cells with features of histiocytes and myofibroblasts that was associated with lens-induced uveitis. The spindle cell mass appears to have arisen as an exaggerated response to exposed lens fibers. Although information from immunohistochemistry and cytogenetics has advanced the classification of inflammatory tumefactions, this case highlights the challenges in establishing the nature of these lesions.

Polypoid Carcinoma of the Oropharynx with Stromal Ossifying Myofibroblastic Proliferation: A Case Report and Literature Review

A 76-year-old man reported a worsening difficulty in swallowing, leading to the inability to eat. Physical examination and CT scan revealed a polypoid mass on the posterior oropharynx and obstructing the oropharyngeal space. Histologically, the surface was ulcerated. In the underlying necrotic rim, there was active granulation tissue, and a proliferation of voluminous, globoid elements with hyperchromatic and irregular nucleus, sometimes arranged in a alveolar aggregate. The core of the lesion contained spindle-like myoid elements in interwoven bundles, with trabeculae of osteoid matrix maturing into calcified bone. Immunohistochemistry documented positivity for cytokeratins, epithelial membrane antigen, and P63 in the globoid elements beneath the necrotic rim; strong and diffuse expression of vimentin, smooth muscle actin, and CD99 and BCL2 in the spindle elements; and complete negativity for cytokeratin 5/6, high molecular weight cytokeratin (clone 34βE12), S100, muscle-specific actin, desmin, CD117, and anaplastic lymphoma kinase. The lesion was morphologically and immunophenotypically classified as a polypoid oropharyngeal carcinoma with ossifying myofibroblastic stromal proliferation.

Unclassified sarcomas: a study to improve classification in a cohort of Golden Retriever dogs

Morphologically, canine soft-tissue sarcomas (STSs) resemble human STSs. In humans, proper classification of STSs is considered essential to improve insight in the biology of these tumors, and to optimize diagnosis and therapy. To date, there is a paucity of data published on the significance of detailed classification of STSs in the dog. We revised a cohort (n = 110) of proliferative lesions obtained from a study in Golden Retrievers that were considered "soft tissue sarcoma, not otherwise specified or of uncertain subtype" in order to optimize the diagnoses of these lesions. The criteria according to the veterinary WHO classification, recent veterinary literature, and the WHO classification for humans were applied. Revision was initially based on morphologic characteristics of hematoxylin and eosin-stained histologic sections of the neoplasms. If considered necessary (n = 76), additional immunohistochemistry was applied to aid characterization. The diagnosis of STS was confirmed in 75 neoplasms (68%). Of this group, diagnosis of a specific subtype of the STSs was possible in 58 neoplasms. Seven neoplasms had morphologic characteristics that were suggestive for sarcoma subtypes only described in the WHO classification for humans. Seventeen neoplasms remained "unclassified STSs." Thirty-one lesions (28%) were diagnosed "neoplasm, not being STS." Four lesions (4%) were considered nonneoplastic. Because incorrect classification of a tumor could lead to inappropriate therapeutic intervention and prognostication, the results of our study clearly illustrate the importance of revision and further diagnosis of "unclassified STSs" in dogs.

Intraneural Nodular Fasciitis in a Child: A Case Report and Review of the Literature

We present the case of an 11-year-old boy with intraneural nodular fasciitis of the median nerve at the distal part of the carpal tunnel. Complete excision of the involved median nerve and cable grafting using 4 fascicular segments of the sural nerve was performed for persistent pain and numbness after initial resection of the tumor in piecemeal fashion. Pain and numbness were completely resolved and there was no evidence of recurrence 24 months after the final surgery.

Myositis ossificans: A rare location in the foot. Report of a case and review of literature

BACKGROUND

Myositis ossificans is a benign, tumor-like lesion characterized by heterotopic ossification of soft tissue that usually affects the elbow and thigh. At different stages of maturity, it show similar histologic appearances with sarcomatous lesions or maturing bone. Misdiagnosis can result in unnecessary radical treatment.

CASE REPORT

A 50-year-old woman with dorsal forefoot soft tissue mass was diagnosed as myositis ossificans after surgical excision and confirmed by a histopathological examination.

DISCUSSION

To our knowledge, myositis ossificans occurrence in the foot is rare and only a few cases have been reported in the literature.

SUMMARY

Increasing awareness on the unusual sites for myositis ossificans occurrence is necessary for differentiating this lesion from a malignant soft- tissue tumors and avoiding diagnostic pitfalls and unnecessary investigations, which can have major consequences and complications for patients.

Massive localized lymphedema: a clinicopathologic study of 46 patients with an enrichment for multiplicity

Massive localized lymphedema is a monstrous tumefactive pseudosarcoma seen in middle-aged morbidly obese adults. Since its initial description in 1998, the etiology remains unknown, although associations with trauma, surgeries, and hypothyroidism have been reported. Herein, we report the largest study of massive localized lymphedema and expand upon its clinicopathologic features. Fifty-four cases from 46 patients were retrospectively identified from the institutional archives of The Ohio State University Wexner Medical Center between 2002 and 2015. Forty-six patients (21 males and 25 females, mean age 50 years) presented with large masses developing over a 5-60-month period. The majority of patients were Caucasian (n=39). All patients were obese with a mean weight of 384.7 lb and a mean body mass index of 59.6 kg/m(2). Thirty-six patients had a history of atherosclerotic cardiovascular disease and diabetes mellitus type 2 was present in 22 patients. Eight patients had multifocal massive localized lymphedema. The sites included thigh (n=33), abdomen (n=17), suprapubic region (n=1), mons pubis (n=6), scrotum (n=2), perianal region (n=1), and right flank (n=1). Mostly, the clinical impression was benign processes, including pannus or lymphedema pseudotumor. Grossly, the mean weight was 8237 g and the mean size was 53.2 cm. Histologically, eight cases showed a unique pattern of dystrophic calcifications mimicking hyperchromatic, atypical nuclei that might lead to misdiagnosis of liposarcoma, four cases showed focal metaplastic ossification, and three cases showed multinucleated cells in addition to prototypic features of massive localized lymphedema. We report that this is the largest series of massive localized lymphedema. This is a lesion mostly seen in morbidly obese patients and the thigh is the most common site of involvement. We note a marked racial predilection for Caucasians and a tendency towards multiplicity. We suggest that obesity itself and the related metabolic syndrome have an important role in its pathogenesis.

Benign soft tissue lesions that may mimic malignancy

Soft tissue lesions which mimic malignancy (pseudosarcomas), represent a significant diagnostic challenge for pathologists. Many features often associated with malignancy including rapid and infiltrative growth, increased cellularity and mitotic activity, and nuclear pleomorphism are present in benign and reactive conditions. This review highlights repair reactions including nodular fasciitis, proliferative fasciitis/myositis, intravascular papillary endothelial hyperplasia, and fat necrosis; lipoma and spindle cell/pleomorphic lipoma; fibroepithelial stromal (pseudosarcomatoid) polyp; phosphaturic mesenchymal tumor; and myxoma. While not inclusive of every pseudoneoplastic soft tissue lesion, this review emphasizes important diagnostic pitfalls and stresses the value of clinical, pathologic, and radiologic correlation.

Intradermal proliferative fasciitis on the finger

Intradermal nodular fasciitis is a rare but not extraordinary pathological finding with approximately 100 cases reported since originally described in 1990. Intradermal proliferative fasciitis, however, has only been reported twice and both arose in the postauricular region. Herein, we report a third case of intradermal proliferative fasciitis and the first to occur on the finger. This case was also unusual in its slow growth, and complete lack of smooth muscle actin expression that has only been reported once before.

[Value of core needle biopsy in preoperative diagnostics of soft tissue tumors: possibilities and limitations]

The differential diagnosis of soft tissue swellings encompasses a variety of benign, intermediate, low-grade malignant and high-grade neoplastic lesions in addition to tumor-like reactive processes. As treatment of these heterogeneous conditions varies greatly from conservative observation and simple local excision up to extensive radical surgical resection, treatment decisions are based mainly on a precise preoperative histological diagnosis on limited biopsy material. Even for clinically unequivocal sarcomas, the importance of the preoperative histological diagnosis has been increasingly emphasized as different therapeutic regimens have been established for different sarcoma types and the indications for preoperative treatment is influenced by the tumor grade and by the entity itself. Other factors positively influencing the increasing use of core needle biopsy for preoperative tumor diagnosis in soft tissue pathology are the availability of modern high-resolution imaging modalities as well as the establishment of several new second generation immunohistochemical markers and the discovery of entity-specific translocations detected by fluorescence in situ hybridization (FISH) in several sarcoma subtypes. In this review it will be shown that a targeted approach for processing core needle biopsies oriented towards the characteristic topographical, demographic, cytomorphological and architectural features of soft tissue lesions facilitates a precise diagnosis of soft tissue neoplasms in most cases. However, profound knowledge of the different aspects of soft tissue tumor diagnostics and familiarity with the frequent as well as the less common and rare tumor entities and variants is a prerequisite for appropriate interpretation of core needle biopsy findings and for selecting a limited but well-suited marker panel. The utilization of modern immunohistochemistry and/or FISH methods is highly useful for establishing the diagnosis of rare and unusual neoplasms in core needle biopsies.

Child abuse masquerading as a soft tissue sarcoma

Pediatric fasciitides are rare benign lesions that may clinically mimic a malignant sarcoma. Nodular fasciitis, the most common of these fasciitides, rarely occurs in children younger than 5 years of age. Often there is a history of preceding trauma. Herein, we report the case of a 5-month-old boy diagnosed with nodular fasciitis in the setting of nonaccidental trauma.

Intravascular fasciitis involving the flank of a 21-year-old female: a case report and review of the literature

Background

Intravascular fasciitis is an uncommon variant of nodular fasciitis, which is a reactive proliferative lesion of myofibroblasts. Since its identification in 1981, only 32 cases of intravascular fasciitis have been reported in the English literature. The lesion is commonly located in the head, neck, and extremities, with only three cases arising from the trunk. Here we report the fourth case involving the trunk (the flank area).

Case presentation

A 21-year-old African-American female presented with a subcutaneous mass on her flank. Grossly, the mass was red-tan, oval, and well-demarcated, measuring approximately 0.5 cm in diameter. Microscopically, the mass was composed of spindle cells arranged in a swirling and intersecting pattern inside the lumens of two blood vessels. It extended through the vascular walls into the surrounding fibroadipose tissue; in some sections, the spindle cells were intermixed with the perivascular fibrous tissue. Elastin stain revealed remnants of elastic lamina partially surrounding the lesion. The nuclei of the spindle cells were relatively uniform with tapered ends and prominent nucleoli. No significant mitotic activity was observed. Multinucleated giant cells were scattered among the spindle cells, along with infiltrating lymphocytes and extravasated red blood cells. Immunohistochemical stains showed the spindle cells were positive for smooth muscle actin, focally positive for muscle specific actin, and negative for S-100, confirming their myofibroblastic differentiation. The overall morphological and immunohistochemical features are consistent with intravascular fasciitis.

Conclusion

By reporting this rare case, we would like to raise the awareness of this non-neoplastic lesion to avoid misdiagnosing it as a sarcoma with vascular invasion. Previously reported similar cases were also reviewed and compared with this case.

Liposarcomas: diagnostic pitfalls and new insights

Liposarcomas represent the most common histotype among soft tissue sarcomas. However, liposarcomas in fact constitute a heterogeneous group of distinctive lesions that pose several diagnostic difficulties. The current World Health Organization classification of soft tissue and bone tumours recognizes four major liposarcoma subtypes: (i) atypical lipomatous tumour/well-differentiated liposarcoma; (ii) de-differentiated liposarcoma; (iii) myxoid liposarcoma; and (iv) pleomorphic liposarcoma. These four main subgroups are characterized by distinctive morphologies, unique genetic findings as well as distinct clinical behaviour. Accurate classification requires the integration of morphological, immunohistochemical and (in selected situations) genetic findings, and is essential for providing patients with the best available treatments. This review will focus upon the main diagnostic pitfalls encountered in the routine diagnosis of liposarcoma, underlining the diagnostic value of combining morphology with cytogenetics and molecular genetics.

Nuclear DNA-Content in Mesenchymal Lesions in Dogs: Its Value as Marker of Malignancy and Extent of Genomic Instability

DNA-aneuploidy may reflect the malignant nature of mesenchymal proliferations and herald gross genomic instability as a mechanistic factor in tumor genesis. DNA-ploidy and -index were determined by flow cytometry in canine inflammatory or neoplastic mesenchymal tissues and related to clinico-pathological features, biological behavior and p53 gene mutational status. Half of all sarcomas were aneuploid. Benign mesenchymal neoplasms were rarely aneuploid and inflammatory lesions not at all. The aneuploidy rate was comparable to that reported for human sarcomas with significant variation amongst subtypes. DNA-ploidy status in canines lacked a relation with histological grade of malignancy, in contrast to human sarcomas. While aneuploidy was related to the development of metastases in soft tissue sarcomas it was not in osteosarcomas. No relation amongst sarcomas was found between ploidy status and presence of P53 gene mutations. Heterogeneity of the DNA index between primary and metastatic sarcoma sites was present in half of the cases examined. Hypoploidy is more common in canine sarcomas and hyperploid cases have less deviation of the DNA index than human sarcomas. The variation in the presence and extent of aneuploidy amongst sarcoma subtypes indicates variation in genomic instability. This study strengthens the concept of interspecies variation in the evolution of gross chromosomal aberrations during cancer development.