Nodular fasciitis | |
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Other names | Nodular pseudosarcomatous fasciitis, subcutaneous pseudosarcomatous fibromatosis |
Micrograph of nodular fasciitis showing the haphazard arrangement of cells (tissue culture-like pattern). H&E stain. | |
Specialty | Rheumatology |
Types | Cranial fasciitis, intravascular fasciitis |
Nodular fasciitis (NF) is a benign, soft tissue tumor composed of myofibroblasts that typically occurs in subcutaneous tissue, fascia, and/or muscles. [1] [2] [3] [4] The literature sometimes titles rare NF variants according to their tissue locations. The most frequently used and important of these are cranial fasciitis [5] and intravascular fasciitis. [6] In 2020, the World Health Organization classified nodular fasciitis as in the category of benign fibroblastic/myofibroblastic tumors. [7] NF is the most common of the benign fibroblastic proliferative tumors of soft tissue. [4]
Nodular fasciitis is a rapidly growing, usually self-limiting neoplasm that occurs primarily but not exclusively in adults. Due to its rapid growth, NF is often misdiagnosed as a malignant tumor, usually a sarcoma. [8] Indeed, NF was originally termed subcutaneous pseudosarcomatous fibromatosis when first described in 1955 by Konwaler et al. [9] The correct diagnosis of a tumor as NF is pivotal to prevent its overtreatment as a more aggressive or malignant growth. [8]
While nodular fasciitis may be precipitated by localized injuries, recent studies indicate that NFs are true neoplasms (i.e. abnormal proliferations of cells without any precipitating event). Up to 92% of NF cases have a specific type of fusion gene in their tumor cells which may be responsible for disrupting the regulation of cell growth and death.
Nodular fasciitis occurs in all age groups but most often affects those between 20–40 years old. Males and females are equally affected. NF tumors, which may be tender or painful, typically present as rapidly growing solitary lesions that reach their final size (usually 2–3 cm) within a few weeks. [10] They are located in the upper limbs (39–54% of cases), trunk (15–20% of cases), lower limbs (16–18% of cases), and head or neck area (20% of cases). Involvement of the head or neck area is more commonly observed in children. [4] Cases of NF in joints [11] or nerves [12] are rare, but do occur. Individual cases of NF have been reported to occur in the bladder, prostate, tongue, lower female genital tract, and parotid gland. In some cases, NF tumors have regressed after incisional biopsy. [4]
The cranial fasciitis variant of NF occurs in the soft and hard cranial tissues of the outer layers of the skull. [5] Patients with this variant are more commonly males than females, and almost exclusively between 3 weeks and 6 years of age. They typically present with a tumor in areas of the head that lay directly over the temporal or parietal bones. Individual cases have been reported to occur in the lower jaw, frontonasal region, anterior nasal spine, the orbit, and maxilla. Characteristically, the tumor is rapidly enlarging, non-painful, rarely regressing without treatment, and potentially expanding into the skull's interior. [13]
In a review of 50 cases, the intravascular fasciitis variant of NF occurred in individuals aged 6 months to 66 years (median age 27 years), with males and females being equally affected (52%:48%). Individuals with this variant commonly present with a blood vessel-localized tumor in the head and neck area (34% of cases), lower extremities (32% of cases), upper extremities (20% of cases), or trunk (14% of cases). The tumors originate in the small blood vessels of the oral mucosa, eyes, lips, cheeks, tongues, and subcutaneous tissue of the extremities (78% of all cases). About 18% of cases involve major veins. The presenting symptoms of these tumors are strictly dependent on their locations and impacts on the involved vasculature. Most cases involving superficial sites present with a small (mean diameter of 1.5 cm), painless, slowly growing mass. However, tumors growing in deep tissues can go unnoticed until they became large enough (e.g. 15 cm) to obstruct blood flow. Cases involving the ascending aorta can present with the signs and symptoms of acute aortic dissection (e.g. severe pain, heart failure, cardiac arrest, fainting, stroke, ischemic peripheral neuropathy, and/or paraplegia), while cases involving large veins may present with acute swelling, pain, and tissue/organ dysfunctions in the areas drained by the involved veins. [6]
The microscopic histopathology of hematoxylin and eosin stained nodular fasciitis tumors consists of spindle-shaped myofibroblastic cells. [8] These cells are in a myxoid or a collagenous (high content of collagen fibers) tissue background. The neoplastic myofibroblasts are arranged in whorls and/or short bundles. These cells may show high rates of replicating as judged by their mitotic index, but these mitoses are normal in appearance. The tumor tissues often contain red blood cells, lymphocytes, and giant osteoclast-like cells, and may contain sites of bone-like tissue. [10] NF is sometimes classified into three subtypes based on its predominant histopathological pattern: myxoid or reactive (type I), cellular (type II), and fibrous (type III). [4] These patterns appear related to the duration of the lesion, with the myxoid variant tending to have the shortest duration and the cellular and fibrous variants tending to have progressively longer durations. [14] Immunohistochemical analyses indicate that the cells in NF usually express smooth muscle actin, muscle specific actin, and vimentin proteins but generally do not express CD34, S-100 protein, desmin, trypsin, factor VIII, F4/80, or HLA-DR1 proteins. [10] Uncommonly, the cells in NF tumors express the CD68 (a histiocyte-specific marker) protein. [4]
The histopathology and expressions of marker proteins in cranial fasciitis tumors tend to be more organized and have higher levels of inflammatory cell infiltrates, vascularity, and involvements of underlying bone than NF. [13]
The histopathology and expressions of marker proteins in intravascular fasciitis tumors tend to be arranged in a storiformed or haphazard pattern and have vesicle-containing nuclei with prominent nucleoli. [6]
Until recently, nodular fasciitis was considered a reaction to trauma at the site where the tumor subsequently developed. [15] However, recent findings indicate that up to 92% of NF tumors involve the self-limiting growth of a clone of neoplastic cells that contain a fusion gene. Fusion genes are abnormal genes consisting of parts from two different genes that form as a result of large scale gene mutations such as chromosomal translocations, interstitial deletions, or inversions. The fusion gene found in NF tumor cells consists of a part of the USP6 gene combined with any one of numerous other genes. Its most common partner gene in NF is the MYH9 (myosin-9) gene. [5] [10] This USP6-MYH9 fusion gene forms as a result of a translocation of part of the USP6 gene located at band 13.2 on the long (or "q") arm of chromosome 17, [16] with part of the MYH9 gene at band 13.2 on the short (or "p") arm of chromosome 22. [17] Other genes that partner with the USP6 gene to form a fusion gene found in NF include: RRBP1 (ribosome binding protein 1), CALU (calumenin), CTNNB1 (catenin beta 1), MIR22HG , [17] [18] SPARC (secreted protein acidic and cysteine rich), THBS2 (thrombospondin-2), COL6A2 (collagen type VI alpha 2 chain), SEC31A , EIF5A (eukaryotic translation initiation factor 5A), COL1A1 (collagen type I alpha 1 chain), COL1A2 (collagen type I alpha 2 chain), COL3A1 (collagen type III alpha 1 chain), PAFAH1B1 (platelet activating factor acetylhydrolase 1b regulatory subunit 1), SERPINH1 (serpin family H member 1), [10] PDLIM7 (PDZ and LIM domain protein 7), and MYL12A (myosin regulatory light chain 12A) gene. [19] While very few cases have been analyzed to date, USP6-containing fusion genes have been found in the tumor cells of 7 of 15 tested cases of cranial fasciitis [5] [20] and six of six tested cases of intravascular fasciitis. [6] [11] [21] [22]
All of the USP6-containing fusion genes in NF and variants overproduce a chimeric protein containing a part of the USP6 gene's product, ubiquitin carboxyl-terminal hydrolase 6a, that has uncontrolled deubiquitinating enzyme activity. This may result in the inappropriate stimulation of multiple cell signaling pathways, including the Wnt signaling pathway, one of the JAK-STAT signaling pathways, the c-Jun signaling pathway, [10] and the NF-κB signaling pathway. [23] Each of these pathways, when inappropriately activated, has been implicated in promoting the development of various tumors and cancers. [10] Further studies are needed to determine which, if any, of these pathways are overactive and can be successfully targeted with specific drug therapies to treat NF and its variants. [8] [10]
Two cases of NF have shown tumor cells in which the USP6 gene has fused with the PPP6R3 [24] gene. In both of these cases, the tumors clearly showed malignant behavior. [10] [25] [26]
NF may resemble and therefore be misdiagnosed as dermatofibrosarcoma protuberans, fibrosarcoma, malignant fibrous histiocytoma, spindle-cell melanoma, [27] leiomyosarcoma, [4] or inflammatory myofibroblastic tumor. [8] The diagnosis of NF and its variants depends on a combination of findings, no single one of which is definitive. These include: presentation (especially location in the cranium, within blood vessels, or outside of these areas); histopathology (analyses of tumor cell mitoses which, if atypical, strongly suggest the tumor is not NF); [8] presence of myofibroblasts that typically express muscle-specific actin, SMA, and vimentin, may express CD68, but generally do not express S100, desmin, trypsin, factor VIII, F4/80, or CD34; [8] and presence of typical neoplastic cells expressing an USP6-containing fusion gene. [8]
While virtually all cases of NF and variants have had excellent prognoses, the two cases of individuals with an USP6-PPP6R3 fusion gene in their NF tumor cells had less favorable prognoses: their tumors were locally invasive, repeatedly relapsed after surgical removal, and grew progressively larger over 2 and 10 years of observations. [10] [25] [26]
Some cases of NF have regressed after being partially biopsied, suggesting that a watchful waiting approach may be appropriate after biopsy in some cases. [10] [4] The most common and generally accepted first-line treatment for cases of NF, craniofacial fasciitis, and intravascular fasciitis tumors is surgical removal. In almost all cases this removal is curative, and tumor recurrences are uncommon, even in cases where the tumor is only partially removed. [4] Furthermore, tumor recurrences are typically cured by simple re-excisions. [10] NF cases have also been successfully treated with corticosteroid drugs (e.g. triamcinolone) injected directly into the tumor. [5] [4] This treatment has been most often used for patients with recurrent tumors. [28] Some studies, however, have suggested reevaluating the diagnosis in recurrent NF tumors to ensure the diagnosis is correct. [29] Surgical and corticosteroid interventions may need to be performed promptly in order to a cranial tumor from expanding into the skull's interior [13] or an intravascular tumor from compromising blood flood flow. [6]
Two cases of NF in which tumor cells expressed a USP6-PPP6R3 fusion gene had highly aggressive, locally invasive, repeatedly recurrent, and progressively enlarging tumors over 2 and ten years. [25] [26] One case developed multiple metastases that were partially controlled with radiation therapy. [25] The other case was treated by wide surgical resection of the tumor; this case did not have metastatic disease and one year after the wide resection had no recurrences. [26]
Intravascular lymphomas (IVL) are rare cancers in which malignant lymphocytes proliferate and accumulate within blood vessels. Almost all other types of lymphoma involve the proliferation and accumulation of malignant lymphocytes in lymph nodes, other parts of the lymphatic system, and various non-lymphatic organs but not in blood vessels.
Ubiquitin carboxyl-terminal hydrolase 6 (USB6), also termed TRE17 and Tre-2, is a deubiquitinating enzyme that in humans is encoded by the hominid USP6 gene located at band 13.2 on the short arm of chromosome 17. Deubiquitinating enzymes (DUBs) are enzymes that act within cells to remove ubiquitins from various functionally important proteins. Ubiquitin enzymes add ubiquitin to these proteins and thereby regulate their cellular location, alter their activity, and/or promote their degradation. By deubiquitinating these proteins, DUBs counter the effects of the ubiquinating enzymes and contribute to regulating the actions of the targeted proteins. In normal adult tissues, USP6 is highly expressed in testicle tissue, modestly expressed in ovarian tissue, and absent or minimally expressed in other tissues. It is also highly expressed in fetal brain tissue. The specific functions of USP6 are poorly defined primarily because its presence is restricted to primates: there are no available animal models to determine the effects of its deletion, although some studies suggest that UPSP6 contributes to normal brain development. In all events, USP6 has gained wide interest because of its abnormally increased expression by the neoplastic cells in various tumors derived from mesenchymal tissue.
Giant cell fibroblastoma (GCF) is a rare type of soft-tissue tumor marked by painless nodules in the dermis and subcutaneous tissue. These tumors may come back after surgery, but they do not spread to other parts of the body. They occur mostly in boys. GCF tumor tissues consist of bland spindle-shaped or stellate-shaped cells interspersed among multinucleated giant cells.
Poromas are rare, benign, cutaneous adnexal tumors. Cutaneous adnexal tumors are a group of skin tumors consisting of tissues that have differentiated towards one or more of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. Poromas are eccrine or apocrine sweat gland tumors derived from the cells in the terminal portion of these glands' ducts. This part of the sweat gland duct is termed the acrosyringium and had led to grouping poromas in the acrospiroma class of skin tumors. Here, poromas are regarded as distinct sweat gland tumors that differ from other sweat gland tumors by their characteristic clinical presentations, microscopic histopathology, and the genetic mutations that their neoplastic cells have recently been found to carry.
Low-grade fibromyxoid sarcoma (LGFMS) is a rare type of low-grade sarcoma first described by H. L. Evans in 1987. LGFMS are soft tissue tumors of the mesenchyme-derived connective tissues; on microscopic examination, they are found to be composed of spindle-shaped cells that resemble fibroblasts. These fibroblastic, spindle-shaped cells are neoplastic cells that in most cases of LGFMS express fusion genes, i.e. genes composed of parts of two different genes that form as a result of mutations. The World Health Organization (2020) classified LGFMS as a specific type of tumor in the category of malignant fibroblastic and myofibroblastic tumors.
Inflammatory myofibroblastic tumor (IMT) is a rare neoplasm of the mesodermal cells that form the connective tissues which support virtually all of the organs and tissues of the body. IMT was formerly termed inflammatory pseudotumor. Currently, however, inflammatory pseudotumor designates a large and heterogeneous group of soft tissue tumors that includes inflammatory myofibroblastic tumor, plasma cell granuloma, xanthomatous pseudotumor, solitary mast cell granuloma, inflammatory fibrosarcoma, pseudosarcomatous myofibroblastic proliferation, myofibroblastoma, inflammatory myofibrohistiocytic proliferation, and other tumors that develop from connective tissue cells. Inflammatory pseudotumour is a generic term applied to various neoplastic and non-neoplastic tissue lesions which share a common microscopic appearance consisting of spindle cells and a prominent presence of the white blood cells that populate chronic or, less commonly, acute inflamed tissues.
Mammary-type myofibroblastoma (MFB), also named mammary and extramammary myofibroblastoma, was first termed myofibrolastoma of the breast, or, more simply, either mammary myofibroblastoma (MMFB) or just myofibroblastoma. The change in this terminology occurred because the initial 1987 study and many subsequent studies found this tumor only in breast tissue. However, a 2001 study followed by numerous reports found tumors with the microscopic histopathology and other key features of mammary MFB in a wide range of organs and tissues. Further complicating the issue, early studies on MFB classified it as one of various types of spindle cell tumors that, except for MFB, were ill-defined. These other tumors, which have often been named interchangeably in different reports, are: myelofibroblastoma, benign spindle cell tumor, fibroma, spindle cell lipoma, myogenic stromal tumor, and solitary stromal tumor. Finally, studies suggest that spindle cell lipoma and cellular angiofibroma are variants of MFB. Here, the latter two tumors are tentatively classified as MFB variants but otherwise MFB is described as it is more strictly defined in most recent publications. The World Health Organization in 2020 classified mammary type myofibroblastoma tumors and myofibroblastoma tumors as separate tumor forms within the category of fibroblastic and myofibroblastic tumors.
Acral myxoinflammatory fibroblastic sarcoma (AMSF), also termed myxoinflammatory fibroblastic sarcoma (MSF), is a rare, low-grade, soft tissue tumor that the World Health Organization (2020) classified as in the category of rarely metastasizing fibroblastic and myofibroblastic tumors. It is a locally aggressive neoplasm that often recurs at the site of its surgical removal. However, it usually grows slowly and in only 1–2% of cases spreads to distant tissues.
Proliferative fasciitis and proliferative myositis (PF/PM) are rare benign soft tissue lesions that increase in size over several weeks and often regress over the ensuing 1–3 months. The lesions in PF/PM are typically obvious tumors or swellings. Historically, many studies had grouped the two descriptive forms of PF/PM as similar disorders with the exception that proliferative fasciitis occurs in subcutaneous tissues while proliferative myositis occurs in muscle tissues. In 2020, the World Health Organization agreed with this view and defined these lesions as virtually identical disorders termed proliferative fasciitis/proliferative myositis or proliferative fasciitis and proliferative myositis. The Organization also classified them as one of the various forms of the fibroblastic and myofibroblastic tumors.
Lipofibromatosis (LPF) is an extremely rare soft tissue tumor which was first clearly described in 2000 by Fetsch et al as a strictly pediatric, locally invasive, and often recurrent tumor. It is nonetheless a non-metastasizing, i.e. benign, tumor. While even the more recent literature has sometimes regarded LPF as a strictly childhood disorder, rare cases of LPF have been diagnosed in adults. The diagnosis of lipofibromatosis should not be automatically discarded because of an individual's age.
Fibroblastic and myofibroblastic tumors (FMTs) are tumors which develop from the mesenchymal stem cells which differentiate into fibroblasts and/or the myocytes/myoblasts that differentiate into muscle cells. FMTs are a heterogeneous group of soft tissue neoplasms. The World Health Organization (2020) defined tumors as being FMTs based on their morphology and, more importantly, newly discovered abnormalities in the expression levels of key gene products made by these tumors' neoplastic cells. Histopathologically, FMTs consist of neoplastic connective tissue cells which have differented into cells that have microscopic appearances resembling fibroblasts and/or myofibroblasts. The fibroblastic cells are characterized as spindle-shaped cells with inconspicuous nucleoli that express vimentin, an intracellular protein typically found in mesenchymal cells, and CD34, a cell surface membrane glycoprotein. Myofibroblastic cells are plumper with more abundant cytoplasm and more prominent nucleoli; they express smooth muscle marker proteins such as smooth muscle actins, desmin, and caldesmon. The World Health Organization further classified FMTs into four tumor forms based on their varying levels of aggressiveness: benign, intermediate, intermediate, and malignant.
Lipofibromatosis-like neural tumor (LPF-NT) is an extremely rare soft tissue tumor first described by Agaram et al in 2016. As of mid-2021, at least 39 cases of LPF-NT have been reported in the literature. LPF-NT tumors have several features that resemble lipofibromatosis (LPF) tumors, malignant peripheral nerve sheath tumors, spindle cell sarcomas, low-grade neural tumors, peripheral nerve sheath tumors, and other less clearly defined tumors; Prior to the Agaram at al report, LPF-NTs were likely diagnosed as variants or atypical forms of these tumors. The analyses of Agaram at al and subsequent studies uncovered critical differences between LPF-NT and the other tumor forms which suggest that it is a distinct tumor entity differing not only from lipofibromatosis but also the other tumor forms.
The PPP6R3 gene is located at band 13.2 on the long arm of chromosome 11 and is expressed in all tissues tested in humans. It encodes protein phosphatase 6 regulatory subunit 3 (PP6RS3). Also termed serine/threonine-protein phosphatase 6 regulatory subunit 3, PP6RS3 is the function-regulating subunit of protein phosphatase 6 (PPP6C). PPP6C is a component of a signaling pathway that regulates various cell functions including cell division, the repair of damaged DNA, inflammatory responses, messenger mRNA splicing, and the stability of chromosomes.
Sclerosing epithelioid fibrosarcoma (SEF) is a very rare malignant tumor of soft tissues that on microscopic examination consists of small round or ovoid neoplastic epithelioid fibroblast-like cells, i.e. cells that have features resembling both epithelioid cells and fibroblasts. In 2020, the World Health Organization classified SEF as a distinct tumor type in the category of malignant fibroblastic and myofibroblastic tumors. However, current studies have reported that low-grade fibromyxoid sarcoma (LGFMS) has many clinically and pathologically important features characteristic of SEF; these studies suggest that LGSFMS may be an early form of, and over time progress to become, a SEF. Since the World Health Organization has classified LGFMS as one of the malignant fibroblastic and myofibroblastic tumors that is distinctly different than SEF, SEF and LGFMS are here regarded as different tumor forms.
Mammary secretory carcinoma (MSC), also termed secretory carcinoma of the breast, is a rare form of the breast cancers. MSC usually affects women but in a significant percentage of cases also occurs in men and children. Indeed, McDvitt and Stewart first described MSC in 1966 and termed it juvenile breast carcinoma because an increased number of cases were at that time diagnosed in juvenile females. MSC is the most common form of breast cancer in children, representing 80% of childhood breast cancers, although it accounts for less than 0.15% of all breast cancers.
The FET protein family consists of three similarly structured and functioning proteins. They and the genes in the FET gene family which encode them are: 1) the EWSR1 protein encoded by the EWSR1 gene located at band 12.2 of the long arm of chromosome 22; 2) the FUS protein encoded by the FUS gene located at band 16 on the short arm of chromosome 16; and 3) the TAF15 protein encoded by the TAF15 gene located at band 12 on the long arm of chromosome 7 The FET in this protein family's name derives from the first letters of FUS, EWSR1, and TAF15.
Ischemic fasciities (IF), also termed atypical decubital fibroplasia or decubital ischemic fasciitis, is a rare pseudosarcomatous tumor. It was first described by E. A. Montgomery et al. in 1992. This tumor typically forms in the subcutaneous tissues that overlie bony protuberances such as a hip in individuals who are debilitated and bed-ridden.
Angiofibroma of soft tissue (AFST), also termed angiofibroma, not otherwise specified, is a recently recognized and rare disorder that was classified in the category of benign fibroblastic and myofibroblastic tumors by the World Health Organization in 2020. An AFST tumor is a neoplasm that was first described by A. Mariño-Enríquez and C.D. Fletcher in 2012.
Dermatofibrosarcoma protuberans, fibrosarcomatous (DFSP-FS), also termed fibrosarcomatous dermatofibrosarcoma protuberans, is a rare type of tumor located in the dermis. DFSP-FS tumors have been viewed as: 1) a more aggressive form of the dermatofibrosarcoma protuberans (DFSP) tumors because they have areas that resemble and tend to behave like malignant fibrosarcomas or 2) as a distinctly different tumor than DFSP. DFSP-FS tumors are related to DFSP. For example, surgically removed DFSP tumors often recur with newly developed fibrobosarcoma-like areas. Nonetheless, the World Health Organization (WHO), 2020, classified DFSP and DFSP-FS as different tumors with DFSP being in the category of benign and DFSP-FS in the category of rarely metastasizing fibroblastic and myofibroblastic tumors. This article follows the WHO classification: the 5-15% of DFSP tumors that have any areas of fibrosarcomatous microscopic histopathology are here considered DFSP-FS rather than DFSP tumors.
CYLD cutaneous syndrome (CCS) encompasses three rare inherited cutaneous adnexal tumor syndromes: multiple familial trichoepithelioma (MFT1), Brooke–Spiegler syndrome (BSS), and familial cylindromatosis (FC). Cutaneous adnexal tumors are a large group of skin tumors that consist of tissues that have differentiated towards one of the four primary adnexal structures found in normal skin: hair follicles, sebaceous sweat glands, apocrine sweat glands, and eccrine sweat glands. CCS tumors are hair follicle tumors.