Intramuscular nodular fasciitis of the rectus abdominis muscle in an 11-year-old girl

Case report: Large-size intramuscular nodular fasciitis, a challenging histopathologic diagnosis confirmed by molecular detection of USP6 gene rearrangement: Case report and literature review

The intramuscular subtype of nodular fasciitis (NF) is rare with lesions normally not more than 2 cm in size and characterized by pseudosarcomatous morphology. We report a case of a 27-year-old man with a large-size intramuscular NF. The patient came for treatment complaining of an increasingly enlarged mass in the left upper arm for 4 months. Magnetic resonance imaging (MRI) confirmed the presence of a well-defined tumor measuring 5 cm within the outer edge of the middle humerus. Microscopically, the neoplasm was rich in fibroblasts and myofibroblasts in an interlaced pattern with high mitotic index and evident multinuclear giant cells. Erythrocyte extravasation was easily seen in the stroma. The tumor border was infiltrative. Immunohistochemically, the tumor cells were positive for smooth muscle actin (SMA) and negative for cytokeratin, desmin, H-Caldesmon, CD34, S100, ALK, and β-catenin. Fibrosarcoma was highly suspected by histopathological and immunohistochemical examination. Molecular detection demonstrated evidence of ubiquitin-specific peptidase 6 (USP6) gene rearrangement in this tumor. Based on the findings, the tumor was diagnosed as intramuscular NF. At 56 months after the initial surgery, the patient had recovered with no evidence of recurrence or metastasis. Large-size intramuscular NF is very rare and easily overdiagnosed as malignant tumor due to its obvious pseudosarcomatoid pathological features. USP6 gene rearrangement detection can effectively avoid this major misdiagnosis.

Intramuscular diffuse-type tenosynovial giant cell tumor of the deltoid muscle in a child

Tenosynovial giant cell tumors (GCTs) typically form in the joints or extra-articular soft tissues such as the tendon sheath, and are benign tumors that commonly occur in the hands or wrists in the third to fifth decades of life. However, the diffuse type of extra-articular GCT arising within muscle is a rare soft tissue tumor, especially in a pediatric patient. In this report, we describe the magnetic resonance imaging and sonographic findings of a rare case of intramuscular diffuse-type GCT in the deltoid muscle of a 9-year-old boy.

Nodular fasciitis on chest wall in a teenager: a case report and review of the literature

We report the case of a 16-year-old boy with a rapid growing mass on his left anterior chest wall. The mass was completely resected, and pathological examination confirmed nodular fasciitis. Benign chest tumors rarely occur in childhood. Nodular fasciitis is a benign proliferation of myofibroblast that is often mimicked by a sarcoma of the soft tissue. Physicians should consider the possibility of nodular fasciitis in chest wall tumors in the pediatric population.

MRI characteristics of nodular fasciitis of the musculoskeletal system

OBJECTIVE

To evaluate MRI imaging appearances of nodular fasciitis in a pathologic-proven series of 29 patients.

MATERIALS AND METHODS

Review of the orthopedic oncology and pathology databases yielded 51 cases of histologically proven nodular fasciitis. MR imaging was available in 29 patients. Three musculoskeletal radiologists retrospectively reviewed all cases in consensus. Imaging features evaluated included location in the body, size, compartmental localization, relationship to fascia, signal characteristics, enhancement pattern, transcompartmental extension, and osseous and intra-articular involvement.

RESULTS

There were 15 male and 14 female patients. Mean age was 33 years (range, 16-59 years). Lesions ranged in size from 1.6 to 9 cm with 84 % of lesions measuring less than 4 cm. Twenty-three lesions were located in the upper arm or shoulder girdle. Nine lesions were subcutaneous in location, nine were intra-muscular, and 11 were inter-muscular. Lesions were consistently ovoid in shape with broad fascial contact. They exhibited internal homogenous low T1 and heterogeneous intermediate T2 signal with surrounding edema and slightly inhomogeneous enhancement. Twelve lesions exhibited central non-enhancing areas. Trans-compartmental spread was demonstrated in nine lesions. Osseous changes were seen in five cases and included extrinsic cortical saucerization, medullary edema, and transcortical osseous invasion. Two lesions demonstrated intra-articular extension.

CONCLUSIONS

MR imaging features of nodular fasciitis are generally non-specific and can be mistaken for a soft tissue sarcoma. This series, the largest MRI series of musculoskeletal cases in the literature, confirms the predilection of nodular fasciitis for the upper extremity in young adults but also demonstrates that aggressive imaging features such as transcompartmental spread, and osseous and intra-articular involvement may be seen in association with this benign soft tissue lesion.