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At least 19 recordsLinked to original sources
PubMed1998

Low-grade myofibroblastic sarcoma: analysis of 18 cases in the spectrum of myofibroblastic tumors.

The clinicopathologic, immunohistochemical, and ultrastructural features of a seemingly distinctive low-grade spindle cell sarcoma showing myofibroblastic differentiation have been analyzed in a series of 18 patients. The age range of the patients (7 women and 11 men) was 19-72 years (median: 42 years). A painless, enlarging mass was the most common clinical presentation. Five tumors arose in the oral cavity (including four lesions in the tongue), four in the lower extremities and three in the upper extremities, four cases in the abdominal/pelvic cavity, and two on the trunk. Eight soft-tissue cases involved skeletal muscle, three cases were located in perifascial tissues, and two arose in subcutaneous tissue. Tumor size ranged from 1.4 to 17 cm (median: 4 cm); in six cases (of which four were abdominal/pelvic) the lesion was larger than 5 cm. All patients were treated surgically, and four received additional adjunctive therapy. Histologically, most cases were cellular lesions showing a diffusely infiltrative pattern, and were composed of spindle-shaped tumor cells arranged mainly in fascicles. Tumor cells had poorly defined, palely eosinophilic cytoplasm and fusiform nuclei, which were either tapering and wavy or plumper and vesicular with indentations and small inconspicuous nucleoli. Tumor cells were set in a collagenous matrix often with prominent hyalinization. Mild nuclear atypia was noted in 16 cases; in the other 2 cases, and in the metastases of one other lesion, a greater degree of nuclear atypia was seen. In all but one case, the mitotic rate ranged from 1 to 6 mitoses in 10 HPFs (mean: 2/10 HPFs); in a single case, there were more than 20 mitoses in 10 HPFs. Immunohistochemically, all cases stained positively for at least one myogenic marker; 12 cases were positive for desmin, 11 for alpha-smooth muscle actin, and 6 for muscle actin (HHF35). Seven neoplasms were desmin positive/ alpha-smooth-muscle actin negative, and five cases were desmin negative/alpha-smooth-muscle actin positive emphasizing the variable immunophenotype of myofibroblastic lesions. In addition, 7 of 10 tumors stained at least focally positive for fibronectin. Ultrastructural examination in five cases showed characteristic features of myofibroblasts. Follow-up in 11 patients (median: 29 months) revealed local recurrence in 2 cases, and multiple distant soft-tissue, intraosseous, and pulmonary metastases in one other patient. Low-grade myofibroblastic sarcoma seems to represent a distinct entity in the spectrum of low-grade myofibroblastic neoplasms and is distinguishable from fibromatosis, myofibromatosis, solitary fibrous tumor, fibrosarcoma, and leiomyosarcoma.

Actins↗
PubMed2026

A systematic literature review on low-grade myofibroblastic sarcoma of the trunk.

BACKGROUND: Low-grade myofibroblastic sarcoma (LGMS) is a rare malignant mesenchymal tumor, with primary trunk involvement being particularly uncommon. Due to its rarity, associated diagnostic challenges, and variability in management, a comprehensive evaluation of the available evidence is required. This study aims to systematically review the clinical characteristics, treatment strategies, and outcomes of truncal LGMS. METHODS: A systematic literature search was conducted using PubMed, Web of Science, and Embase for articles published from January 1998 to January 2026. The review included full-text articles involving patients with a pathologically confirmed diagnosis of truncal LGMS. The collected data included patient demographics, tumor features, treatment modalities, recurrence, and follow-up status. RESULTS: Of the 404 studies initially identified, 30 studies involving 59 patients with pathologically confirmed truncal LGMS met the inclusion criteria. Outcome analyses of therapeutic management and clinical course included 45 patients with complete follow-up data, including 42 surgically treated patients and 3 non-surgically managed patients. The final evidence base consisted solely of retrospective studies and case reports. No prospective studies or randomized controlled trials were identified. Consequently, a descriptive statistical analysis was conducted instead of a meta-analysis. CONCLUSION: Current evidence indicates that wide excision with negative margins may be a reasonable primary treatment option for truncal LGMS, with case-based reports showing numerically lower recurrence after wide excision, although the evidence is limited and potentially confounded by multiple factors. Radiotherapy or chemotherapy may be considered only on a highly individualized basis for selected unresectable, recurrent, metastatic, anatomically constrained, or margin-positive cases. Given the very limited sample size and heterogeneous treatment indications across published cases, treatment efficacy cannot be reliably estimated from the available data. Prolonged long-term regular follow-up is recommended for all patients, considering the risk of late recurrence.

Humans↗
PubMed2026

Low-Grade Myofibroblastic Sarcoma Represents an Epigenetically Distinct Myofibroblastic Tumor With USP6 Upregulation and Stable Genome.

Low-grade myofibroblastic sarcoma (LGMS) is a rare, indolent mesenchymal neoplasm exhibiting myofibroblastic differentiation, with a propensity for local recurrence. The molecular basis of LGMS and its precise relationship with other histological mimics have remained largely undefined. To address this gap, we conducted the first comprehensive multiomics analysis of 6 LGMS cases, integrating whole-exome sequencing, RNA sequencing, and Illumina Methylation EPICv2 array profiling with comparative analysis against public sarcoma methylation cohorts and related fibroblastic tumors. Clinically, patients (median age 35.5 years) presented with small tumors (median size 1.45 cm), predominantly located in the head and neck, displaying classic histological features of diffusely infiltrative spindle cell fascicles with patchy mononuclear inflammation. Two of the 5 patients with follow-up developed local recurrence, and none metastasized (median follow-up duration 92.5 months). Genomically, all LGMS exhibited a low tumor mutational burden (median 2.31 mut/Mb) and a minimal fraction of genome altered, with TP53 and TSC2 deletions and NTRK1 and ERBB3 amplifications found in a subset of cases. No pathogenic fusions were detected. Transcriptomic profiling revealed a distinct signature featuring prominent USP6 overexpression and upregulation of inflammatory and immune-related genes, including CD274 (PD-L1), and enrichment of inflammatory and interferon-gamma response signatures. Epigenetically, LGMS formed a unique methylation cluster closest to inflammatory myofibroblastic tumor, with numerous differentially methylated regions and higher immune infiltration, particularly monocytes, compared with other fibroblastic tumors. These findings establish LGMS as a genomically stable, epigenetically distinct myofibroblastic sarcoma driven by USP6 overexpression and an inflammation-enriched transcriptome. They support its recognition as a standalone entity, facilitate integration into methylation-based sarcoma classifiers for improved diagnostic precision, and nominate USP6-associated pathways and immune checkpoint blockade as promising therapeutic strategies for recurrent or unresectable disease.

Humans↗
PubMed2001

A case of cutaneous low-grade myofibroblastic sarcoma.

A 28-year-old woman presented with a recurrent nodule on the lower margin of her left nostril after laser surgery. Histologically, the nodule had an indistinct margin and was composed of interlacing fascicles of plump, spindled or stellate tumor cells with mild cytologic atypia. The tumor cells were revealed to be myofibroblasts by positivity to smooth muscle actin and negativity to desmin. A diagnosis of low grade myofibroblastic sarcoma (LGMS) was made.

Actins↗
PubMed1998

Inflammatory fibrosarcoma: update, reappraisal, and perspective on its place in the spectrum of inflammatory myofibroblastic tumors.

Inflammatory fibrosarcoma (commonly referred to as inflammatory myofibroblastic tumor) has become increasingly recognized as part of a spectrum of inflammatory myofibroblastic proliferations. It is a potentially locally aggressive myofibroblastic tumor that occurs predominantly in the mesentery of children and young adults. No reliable morphological parameters have been identified that predict prognosis. We evaluated the ultrastructural and immunophenotypic features of 16 cases of inflammatory fibrosarcoma and studied Ki67 (MIB1), PCNA, bcl-2, and p53 in an effort to identify prognostic markers. p53 was not detected immunohistochemically in any case. None of the markers were found to correlate with local recurrences, metastases, or tumor deaths. Low proliferative activity (Ki67 < 10%) was seen in all cases. A characteristic immunophenotype was reconfirmed in which lesional myofibroblasts stained for vimentin, alpha-smooth muscle actin, cytokeratins, and rarely desmin. Ultrastructural studies of seven cases confirmed the presence of a fibroblastic-myofibroblastic spectrum. Because inflammatory myofibroblastic tumor-inflammatory fibrosarcoma is associated with systemic symptoms, polymerase chain reaction studies for Epstein-Barr virus (EBV) and cytomegalovirus (CMV) were performed in 12 cases. Evaluable results in nine cases did not show evidence of either virus. The results of this study indicate that inflammatory fibrosarcoma has a low proliferative activity, which is in keeping with the impression that this is a low-grade sarcoma; that myofibroblasts can participate in true neoplasia; and that EBV and CMV do not play a role in the pathogenesis of inflammatory fibrosarcoma. The variable phenotype of the myofibroblast and its role in reactive and neoplastic processes are discussed. A perspective on the position of inflammatory fibrosarcoma in the spectrum of inflammatory myofibroblastic tumors is also given in light of the current study and the literature.

Adolescent↗
PubMed1978

A sarcoma of myofibroblasts: an ultrastructural study.

A low-grade spindle cell sarcoma was shown by electron microscopy to be composed of myofibroblasts. It is suggested that the occurrence of myofibroblasts in spindle cell sarcomas might be of prognostic significance and that a systematic study to elucidate this point would be a valuable exercise.

Adolescent↗
PubMed2000

Sarcomatoid carcinomas of the upper aerodigestive tracts.

Sarcomatoid carcinoma of the upper aerodigestive tract continues to be one of the most difficult diagnostic challenges for surgical pathologists. Histogenesis has been settled in favor of a divergent (mesenchymal) differentiation of a carcinoma, most often a squamous cell carcinoma. Finding the carcinoma and/or its immunohistochemical marker in the metaplastic cells establishes the diagnosis. There are, however, lesions that can simulate sarcomatoid carcinomas to varying degrees, and in which neither a definable carcinoma nor immunohistochemical evidence of one can be found. Such lesions fall into several categories: 1. benign reactive lesions, 2. inflammatory myofibroblastic tumors, 3. sarcomas, usually low-grade, 4. atypical pseudosarcomatous proliferation. The clinicopathologic considerations of sarcomatoid carcinomas are presented in this context and include immunohistochemical findings, prognostic factors, and biologic course.

Carcinosarcoma↗
PubMed2001

Inflammatory pseudotumor and sarcoma of urinary bladder: differential diagnosis and outcome in thirty-eight spindle cell neoplasms.

We assessed diagnostic criteria among 38 spindle cell tumors of the urinary bladder and obtained follow-up in 36 patients. Patients comprised 28 males and 10 females aged 2.5 months to 87 years. Hematuria was the commonest presenting symptom (27 patients). After review and immunohistochemical workup, 17 patients had inflammatory pseudotumor (myofibroblastic tumor), 4 postoperative spindle cell nodule, 1 leiomyoma, 13 sarcoma (7 low-grade; 6 high-grade), and 3 carcinoma. Mean age was 38 years for pseudotumor (range 15 to 74), 65 for postoperative spindle cell nodule, 51 for sarcoma, and 76 for carcinoma. Size of pseudotumor averaged 4.4 +/- 0.7 cm (range 1.5 to 13.0), similar to sarcoma, 4.0 +/- 0.6 cm (range 0.5 to 7.0). Similar proportions of benign tumors and sarcomas had muscularis propria invasion. The criteria that best differentiated sarcoma from inflammatory pseudotumor were presence of necrosis at the tumor-detrusor muscle interface in muscle-invasive cases, and nuclear atypia. Sarcoma also had less prominent microvasculature, less variable cellularity, consistently > or =1 mitotic figure per 10 high-power fields, and predominant acute inflammation without plasma cells. p53 protein nuclear immunostaining was moderate, unlike the rare to absent staining in pseudotumors. Because all 12 sarcomas were desmin-negative, we did not call them leiomyosarcoma; they overlapped with benign tumor in epithelial, mesenchymal, and actin immunostaining. Among 12 sarcoma patients, 2 died of tumor (at 3 months). Two of four experienced tumor recurrence after partial cystectomy (2 and 26 months). No pseudotumors recurred after transurethral resection or partial cystectomy, although one patient, 5 months after transurethral resection, had histologically identical pseudotumor that the surgeon considered residual. Another patient with pseudotumor, not a candidate for tumor ablation after transurethral resection, had continued tumor growth and he died of urosepsis. In conclusion, inflammatory pseudotumor, although overlapping with sarcoma in presentation, age range, and size, does not metastasize and remains histologically distinct from low-grade sarcoma.

Actins↗
PubMedDate not supplied

Role of electron microscopy in metastatic endometrial stromal tumors.

Endometrial stromal tumors may pose a problem in diagnosis when they appear as metastatic lesions without a known primary tumor. To determine the usefulness of electron microscopy in identifying them in these situations, optimally fixed low-grade stromal sarcomas (five), normal endometrial specimens (six), and malignant mesodermal mixed tumors (four) were studied. The endometrial stromal sarcomas had a general resemblance to normal proliferative endometrial stroma, being composed of undifferentiated cells, fibroblasts, and myofibroblasts. One stromal tumor showed evidence of partial epithelial differentiation. One of the four malignant mesodermal mixed tumors had a fibrosarcomalike component, but there was insufficient resemblance to normal endometrial stroma to indicate a relationship between the two. Together with a review of the literature, this study indicates that electron microscopy is useful in the diagnosis of low-grade endometrial stromal tumors by demonstrating characteristic cellular findings as well as a lack of features specific for other round cell and spindle cell neoplasms.

Aged↗
PubMed1991

Angiomatoid "malignant fibrous histiocytoma": an immunohistochemical study indicative of myoid differentiation.

Six cases of angiomatoid malignant fibrous histiocytoma (MFH), the rarest subtype of MFH, have been studied immunohistochemically using a broad panel of commercially available antisera in formalin-fixed, paraffin-embedded tissue in an attempt to define the pattern of differentiation shown by this unusual tumor. As has been reported in the more common types of MFH, no evidence of histiocytic differentiation was found. However, five cases strongly expressed desmin (DER-11) and two also expressed muscle actin (HHF 35). All tissues examined were negative for myoglobin and alpha-smooth muscle actin. These results provide good evidence for some sort of myogenic or possibly myofibroblastic differentiation in angiomatoid MFH. Given its clinicopathologically and immunohistochemically distinctive features, which are very different from the other variants of MFH, redesignation of angiomatoid MFH as a low-grade myogenic sarcoma of uncertain histogenesis is tentatively proposed. The new term angiomatoid myosarcoma is suggested.

Actins↗
PubMed1999

[Hyalinizing spindle cell tumor with giant rosettes. Case report with immunohistochemical characterization].

This is a case of a 46-years-old male patient with a long-standing history of lower abdominal complaints. A 6-cm measuring tumor was detected by CT and subsequently surgically removed. Classification of this tumor and prognosis was problematic in frozen section and paraffin-embedded material, including immunohistochemical studies. The immunohistochemical findings were compatible with myofibroblastic differentiation of tumor cells. The histologic pattern resembled a "hyalinizing spindle cell tumor with giant rosettes" as recently published. Even if there were certain discrepancies in the immunohistochemical findings in our case, we also recommended treating this tumor as a low-grade sarcoma. The malignancy was also supported by marked proliferative activity demonstrated by MIB 1/KI 67 expression in numerous tumor cells. Finally, it has not yet been determined whether the hyalinizing spindle cell tumor is a pattern associated with a certain cellular differentiation or a pattern common to several mesenchymal tumor types.

Abdominal Neoplasms↗
PubMed1996

Abdominal inflammatory myofibroblastic tumors in children: report of an appendiceal case and review of the literature.

Inflammatory myofibroblastic tumors (IMT) are rare, benign lesions. They mimic, clinically and radiologically, malignant tumors-especially sarcoma. IMT most often are seen in the lung of young adults, but there have been reports of these tumors occurring in children, in various sites. The authors report a case of appendiceal IMT arising in a 15-year-old boy previously treated for inherited distal renal tubular acidosis. He was admitted because of anorexia, weight loss, and a low-grade fever. The ultrasound study showed bilateral hydroureteronephrosis, with a poorly functioning right kidney noted on intravenous urography, and a retrovesical soft-tissue mass. Laboratory studies showed renal insufficiency, an elevated white blood cell count, anemia, thrombocytosis, and hypergammaglobulinemia. During laparotomy, a pelvic appendiceal mass was discovered, appendectomy was performed, and the pathological diagnosis of inflammatory myofibroblastic tumor was made. Three months later the boy was well, and the biological, sonographic, and urographic results had returned to normal. A review of 74 cases of abdominal IMT occurring in childhood emphasizes the importance of pathological differentiation of these lesions from malignancy, with early total excision whenever possible. Long-term follow-up is necessary to detect local recurrence, which may develop many years later, and to confirm the allegedly benign nature of these tumors.

Adolescent↗
PubMed1998

Collagenous fibroma (desmoplastic fibroblastoma): a clinicopathologic analysis of 63 cases of a distinctive soft tissue lesion with stellate-shaped fibroblasts.

Sixty-three cases of collagenous fibroma (desmoplastic fibroblastoma) from the files of the Armed Forces Institute of Pathology were analyzed. These tumors occurred mostly in men (80%) with a median age of 50 years (range, 16 to 81 years). The lesions had a wide anatomic distribution and involved the arm (24%), shoulder girdle (19%), posterior neck or upper back (14%), feet or ankles (14%), leg (14%), hand (8%), and abdominal wall and hip (6%). The patients typically presented with a history of a painless, slowly growing mass, often of relatively long duration. The tumors ranged in size from 1 to 20 cm (median, 3.0 cm). The lesions were predominantly subcutaneous, but fascial involvement was common, and 27% of cases involved skeletal muscle. Gross examination typically showed an elongated, lobulated, or disc-shaped mass with a firm consistency and a homogeneous pearl-gray color. Histologically, the tumors often appeared well marginated on low-power examination, but most (78%) infiltrated fat or, less commonly, skeletal muscle. The lesional cells were relatively bland stellate and spindle-shaped fibroblasts separated by a collagenous or myxocollagenous matrix. Mitotic activity was absent or minimal. Some of the lesional cells had a myofibroblastic immunophenotype, as evidenced by focal reactivity for muscle-specific and alpha-smooth muscle actins. In a few cases, rare actin-positive cells were also positive for keratins. Desmin, S100 protein, and CD34 were not expressed. None of the 39 patients with follow-up (median, 11 years) developed a recurrence. Collagenous fibroma is a benign fibroblastic/myofibroblastic proliferation. The large size of some of these tumors coupled with slow growth and persistence favors a neoplastic process over a peculiar reactive proliferation. The differential diagnosis includes a variety of reactive and neoplastic fibroblastic lesions, most importantly fibromatosis and low-grade fibromyxoid sarcoma. Simple, conservative excision is the treatment of choice for collagenous fibroma.

Adolescent↗
PubMed1997

Latent Epstein-Barr virus infection demonstrated in low-grade leiomyosarcomas of adults with acquired immunodeficiency syndrome, but not in adjacent Kaposi's lesion or smooth muscle tumors in immunocompetent patients.

BACKGROUND: Incidence of smooth muscle tumors is increased in patients with human immunodeficiency virus infection and organ transplant recipients. Smooth muscle tumors in immunocompromised patients often occur in unusual locations and exhibit evidence of latent infection by clonal, presumably tumorigenic, Epstein-Barr virus (EBV). OBJECTIVE: To investigate the presence of EBV latent infection in smooth muscle tumors in patients with acquired immunodeficiency syndrome and in immunocompetent patients. DESIGN: Twenty-two extrauterine, extraintestinal smooth muscle and myofibroblastic tumors were reviewed pathologically, and clinical charts were screened. Tumors were malignant (15 patients), benign (6 patients), and borderline (1 patient). Tissue specimens were investigated for latent EBV infection by latent membrane protein immunocytochemistry and EBV-encoded RNA in situ hybridization. SETTING: University Hospital of the University of Nancy, France. PATIENTS: Patients were 18 adults and four children. Two adults had acquired immunodeficiency syndrome. Both had low-grade leiomyosarcomas located in adrenal gland. Moreover, in patient 1, leiomyosarcoma was multifocal in pericardium and lymph node; in lymph node, muscle tumor was adjacent to nodal and skin Kaposi's lesions. RESULTS: In both patients with acquired immunodeficiency syndrome and leiomyosarcoma, latent infection by EBV could be demonstrated in tumor cells, contrasting with absence of detectable EBV infection in adjacent non-neoplastic tissues and nearby Kaposi's lesions. Latent infection by EBV could not be demonstrated in smooth muscle and myofibroblastic tumors in immunocompetent patients. CONCLUSIONS: Latent EBV infection is associated with smooth muscle cell tumors in immunocompromised patients, but not in immunocompetent patients.

AIDS-Related Opportunistic Infections↗
PubMed1999

Angiomatoid "malignant" fibrous histiocytoma: a clinicopathologic study of 158 cases and further exploration of the myoid phenotype.

Angiomatoid "malignant" fibrous histiocytoma (AMFH) has been considered to be a low-grade sarcoma of childhood, and, with its fibrous pseudocapsule, angiomatoid change, dense lymphoplasmacytic response, and proliferation of spindled or round cells, has been classified as a fibrohistiocytic neoplasm. We wanted to study the clinicopathologic and immunophenotypic features of a large number of these tumors and to especially further explore their myoid differentiation. Cases coded as AMFH from 1979 to 1995 were retrieved from the Soft Tissue Registry of the AFIP. Only cases that met the criteria for AMFH by light microscopy were included, a total of 158 cases. Immunohistochemistry was obtained on 98 cases. Clinical history on 92% of all cases revealed a gender ratio of 1.3 females: males, age range of 2 to 71 years, median size of 2.0 cm, and a distribution of extremities > trunk > head and neck, with 66% lesions occurring in areas of normal lymphoid tissue. All tumors with available margins were well-circumscribed. Eighty percent of cases had some degree of lymphoplasmacytic infiltration; 50% cases had pseudovascular spaces filled with blood. Fifty-two percent had predominantly round cell morphology; 48% had a predominantly spindle cell pattern. Desmin positivity was noted in 51% cases and occurred in both predominantly round cell and spindle cell tumors. Most of the desmin-positive cases with adjacent lymphoid infiltrate (67%) showed scattered similar, desmin-positive cells in the surrounding lymphoid infiltrate, adjacent to the tumor. Muscle-specific and smooth-muscle actins were seen in 14% cases. Heavy-caldesmon was strongly positive in 3%, and calponin was focally positive in 73% and extensively positive in 12% cases. MyoD1, myoglobin, and myogenin (myf4) were negative in all tumors studied. Forty-five percent of cases were positive for CD99; 52% of these had round cell morphology. Fifteen percent of cases were positive for KP-1. All tumors were positive for vimentin and negative for CD21, CD35, S100 protein, CD34, keratins 8/18, and lysozyme. Clinical follow-up on 86 patients indicated that only 1 patient was alive with a local nodal metastasis (1% frequency of metastasis) within 1 year, and 2 others had local recurrence, all over a mean follow-up period of 6 years. The myoid, primarily myofibroblastic, phenotype of these lesions is supported by desmin, calponin, and occasional actin positivity. The occasional heavy-caldesmon and smooth muscle actin additionally suggest rare smooth muscle phenotype; however, lack of skeletal muscle markers indicate no relationship of AMFH to skeletal muscle tumors. The resemblance of these lesions to lymph nodes, clinically and morphologically, the finding of similar desmin positive cells in the adjacent lymphoid infiltrate, and the fact that 66% cases were found in sites of normal lymphoid tissue raise the possibility that some of these lesions may arise from or be related to myoid cells of lymphoid tissue. AMFH has an almost invariably benign behavior, but the 1% metastatic rate warrants its classification as low-grade "malignant." The predominantly round cell, CD99-positive and desmin positive AMFH cases, respectively, should not be confused with Ewing's sarcoma/PNET or rhabdomyosarcoma, respectively.

Adolescent↗
PubMed2001

Myofibrosarcoma: a clinicopathologic study.

The concept of soft tissue sarcomas composed predominantly of myofibroblasts has been controversial. We examined a series of such lesions of low- and intermediate-grade malignancy to further define their clinical and pathologic features. Histologic appearances of four cases diagnosed as myofibrosarcoma by electron microscopy were reviewed. Eleven additional cases with similar morphology were then identified from 249 tumors originally indexed as fibrosarcoma. Electron microscopy was performed on five of these, and immunohistochemistry was carried out on all cases for which material was available. There were 11 men and 4 women aged 33 to 73 years (median, 54 yrs; mean, 53 yrs). Lesions mainly involved the head and neck, extremities, and trunk and ranged in size from 1.5 to 12 cm. The tumors were composed of bland or pleomorphic stellate to spindled cells with eosinophilic cytoplasm and tapered nuclei in a collagenous stroma; 10 were grade 1 and five were grade 2. All sarcomas displayed fascicular or storiform patterns, and some of the grade 1 lesions superficially mimicked nodular fasciitis. Electron microscopy of nine cases showed myofibroblastic differentiation, and immunohistochemistry showed smooth muscle actin in 13 of 15 cases, muscle-specific actin in 7 of 9, desmin in 6 of 14, and cytokeratin in 0 of 11. Four of nine grade 1 and three of four grade 2 tumors recurred (one twice), and one grade 2 tumor metastasized to the lungs. Myofibrosarcomas are indolent low-grade or occasionally aggressive intermediate-grade sarcomas which can be recognized by light microscopy. Their clinical importance lies in the resemblance, particularly of low-grade examples, to reactive or pseudosarcomatous conditions.

Adult↗
PubMedDate not supplied

Myofibroblastoma of the axilla.

A mass in the axilla of a 47-year-old woman was biopsied and resected. The mass was composed of a loosely distributed population of spindle cells that were immunoreactive for smooth-muscle actin. Ultrastructurally, the cells possessed abundant endoplasmic reticulum, and some contained peripheral smooth muscle myofilaments, establishing that they were myofibroblasts. Mitotic activity was sparse, there was no cytologic atypia, and by flow cytometry the tumor was diploid with a low S phase. A diagnosis of myofibroblastoma was favored, although the possibility of a low-grade sarcoma could not be excluded. There has not been any indication of recurrence over a 4-month period of follow-up.

Axilla↗