Rabdomyosarcoma of the Mandible: An Uncommon Clinical Presentation. J Craniofac Surg. 2018;29:e221-e224. [PMID: 29283939 DOI: 10.1097/scs.0000000000004154]

Mimicry of Rhabdomyosarcoma by Tonsillar Actinomycosis: Case Report

Actinomycosis is a rare infectious disease characterized by slowly progressive, chronic suppurative lesions, often mistaken for malignancies due to its ability to mimic them. It is caused by Actinomyces bacteria, which are part of the normal flora of the human oropharynx, gastrointestinal, and urogenital tracts. This case report describes a 51-year-old male with a history of mandibular rhabdomyosarcoma presenting with severe shoulder and hip pain, dysphagia, and headaches, initially suspected to be a cancer recurrence. However, after further investigation, including a PET-CT and tonsillectomy, the diagnosis of actinomycosis was confirmed through histopathological examination. The case highlights the diagnostic challenges of actinomycosis, especially in patients with complex clinical histories, emphasizing the importance of considering it as a differential diagnosis in similar presentations. The patient was treated with long-term antibiotic therapy, predominantly beta-lactams, demonstrating the necessity of a comprehensive diagnostic approach and the implications of a delayed diagnosis. This case underscores the critical need for high clinical suspicion and awareness among healthcare professionals regarding the potential for actinomycosis to mimic more common diseases, ensuring timely and accurate treatment.

Mandibular rhabdomyosarcoma with TFCP2 rearrangement and osteogenic differentiation: a case misdiagnosed as fibrous dysplasia or low-grade central osteosarcoma

Rhabdomyosarcoma with TFCP2-related fusions (TFCP2-RMS) is a rare entity that commonly affects young adults with a predilection for skeletal involvement. We herein report a 40-year-old female patient with TFCP2-RMS who was misdiagnosed as fibrous dysplasia or low-grade central osteosarcoma of the mandible by referring institutions. Histologically, the tumor showed dominant spindle cells and focal epithelioid cells with marked immature woven bone formation. Immunophenotypically, in addition to the characteristic expression of myogenic markers, ALK, and cytokeratins, tumor cells also unusually expressed osteogenic markers, such as MDM2 and SATB2. Through fluorescence in situ hybridization, the tumor cells showed EWSR1::TFCP2 gene fusion and no MDM2 gene amplification. This is a rare case of TFCP2-RMS, which was misdiagnosed as low-grade central osteosarcoma due to its presenting immunophenotype of MDM2 and SATB2, as well as extensive osteoid matrix formation.

Adult rhabdomyosarcoma originating in the temporal muscle, invading the skull and meninges: A case report

BACKGROUND

Rhabdomyosarcoma (RMS) is a rare malignant tumor of mesenchymal origin that mainly affects children. Spindle cell/sclerosing RMS (SSRMS) is even rarer. It is a new subtype that was added to the World Health Organization disease classification in 2013. To the best of our knowledge, this is the first reported case of adult SSRMS disease classification originating in the temporal muscle.

CASE SUMMARY

SSRMS originating in the temporal muscle of a male adult enlarged rapidly, destroyed the skull, and invaded the meninges. The tumor was completely removed, and the postoperative pathological diagnosis was SSRMS. Postoperative recovery was good and chemotherapy and radiotherapy were given after the operation. Followed up for 3 mo, no tumor recurred.

CONCLUSION

RMS is one of the differential diagnoses for head soft tissue tumors with short-term enlargement and skull infiltration. Preoperative computed tomography or magnetic resonance imaging is necessary for early detection of tumor invasion of the skull and brain tissue.

Expanding the Spectrum of Intraosseous Rhabdomyosarcoma: Correlation Between 2 Distinct Gene Fusions and Phenotype

Primary intraosseous rhabdomyosarcomas (RMSs) are extremely rare. Recently 2 studies reported 4 cases of primary intraosseous RMS with EWSR1/FUS-TFCP2 gene fusions, associated with somewhat conflicting histologic features, ranging from spindle to epithelioid. In this study we sought to further investigate the pathologic and molecular abnormalities of a larger group of intraosseous RMSs by a combined approach using targeted RNA sequencing analysis and fluorescence in situ hybridization (FISH). We identified 7 cases, 3 males and 4 females, all in young adults, age range 20 to 39 years (median, 27 y). Three cases involved the pelvis, 2 involved the femur and 1 each involved the maxilla and the skull. Molecular studies identified recurrent gene fusions in all 7 cases tested, including: a novel MEIS1-NCOA2 fusion in 2 cases, EWSR1-TFCP2 in 3 cases, and FUS-TFCP2 gene fusions in 1 case. One case showed a FUS gene rearrangement, without a TFCP2 gene abnormality by FISH. The MEIS1-NCOA2-positive cases were characterized by a more primitive and fascicular spindle cell appearance, while the EWSR1/FUS rearranged tumors had a hybrid spindle and epithelioid phenotype, with more abundant eosinophilic cytoplasm and mild nuclear pleomorphism. Immunohistochemically, all tumors were positive for desmin and myogenin (focal). In addition, 4 tumors with TFCP2-associated gene fusions also coexpressed ALK and cytokeratin. In conclusion, our results suggest a high incidence of gene fusions in primary RMSs of bone, with 2 molecular subsets emerging, defined by either MEIS1-NCOA2 or EWSR1/FUS-TFCP2 fusions, showing distinct morphology and immunophenotype. Additional studies with larger numbers of cases and longer follow-up data are required to definitively evaluate the biological behavior of these tumors and to establish their relationship to other spindle cell RMS genetic groups.

Embryonal Rhabdomyosarcoma (Botryoid Subtype) Affecting the Buccal Mucosa

Rhabdomyosarcoma (RMS) is a rare oral malignant soft tissue tumor whose pathological features may influence the clinical behavior, treatment and prognosis of the lesion. We report a case of a 13-year-old female patient, presenting an asymptomatic polypoid swelling in the left buccal mucosa that was approximately 2.5 cm in diameter and 3 months evolution. The presumptive diagnosis was fibrous hyperplasia and an excisional biopsy was carried out. Pathologic analysis revealed proliferation of predominantly ovoid cells, with eosinophilic cytoplasm and pleomorphic nuclei, arranged in subepithelial cambium layer. The mucosal surface presented a papillary-verrucous appearance. Immunohistochemical analysis revealed intense positivity for desmin, myogenin and Ki-67. The diagnosis was of embryonal RMS (botryoid variant). The patient was subjected to complementary chemotherapy and radiotherapy, with no evidence of recurrence or metastatic disease after 12 months follow-up. A discussion on the clinical, histopathological, immunohistochemical and therapeutic aspects of botryoid RMS will be provided.