UNASSIGNED: Alveolar rhabdomyosarcoma (ARMS) shows a predilection for the peripheral extremities and is very rarely identified as a primary in the brain. Here, we report a case of ARMS with multiple lesions exclusively within the central nervous system (CNS).
UNASSIGNED: A 20-year-old man presented to our hospital with a gradually increasing headache and disturbance of consciousness. Neuroimaging showed hydrocephalus and multiple tumor lesions, including in the brainstem and cerebellum, with uniform gadolinium enhancement on T1-weighted magnetic resonance imaging, as well as spinal cord seeding. Cerebrospinal fluid (CSF) analysis showed a slightly elevated cell count (6/μL; normal, <5/μL) and highly elevated protein (153 mg/dL). In addition, atypical cells were cytologically identified in the CSF. No other laboratory findings were abnormal. Emergency ventricular drainage was performed to control cerebral pressure, followed by a biopsy to confirm the diagnosis. Histological examination revealed a fascicular arrangement of oval cells with eosinophilic cytoplasm and tumor cells with pleomorphic nuclei and prominent nucleoli. Immunohistochemical studies showed negative results for glial fibrillary acidic protein and positive results for desmin and myogenin. In addition, molecular analysis revealed that this tumor had the H3F3A p.Lys28Met mutation and no paired box (PAX)3-forkhead box O1 (FOXO1) or PAX7-FOXO1 fusion genes. ARMS was, therefore, diagnosed. Chemotherapy and radiotherapy were subsequently initiated, but tumor growth could not be controlled, and the patient died 6 months after surgery.
UNASSIGNED: This report describes an extremely rare case of ARMS arising exclusively within the CNS.

Rhabdomyosarcoma (RMS), a malignant mesenchymal neoplasm derived from skeletal muscle, is relatively rare in both human and veterinary medicine. Here we report an unusual case of invasive spindle-cell RMS (SCRMS) with bone infiltration and pathologic fracture in a 3.5-y-old intact female Bulldog. Radiographically, a large, predominantly osteolytic mass in the tibia and fibula of the left hindlimb had features typical of a malignant primary bone tumor. Clinically, osteosarcoma was suspected, and the leg was amputated. Histologically, the mass was composed of loosely interwoven spindle-cell fascicles; tumor cells were fusiform with cigar-shaped nuclei and abundant eosinophilic cytoplasm. The neoplastic cells were strongly immunopositive for vimentin, muscle-specific actin, desmin, myogenin, and myoD1. Invasive SCRMS with osteolysis was diagnosed based on the histologic examination and immunohistochemical (IHC) stains. The dog was alive without any evidence of local recurrence or distant metastasis 18 mo post-surgery. RMS should be included in the differential diagnosis when osteolysis occurs; IHC staining confirmation is of great value for definitive diagnosis and treatment planning.

Extraskeletal Ewing\'s sarcoma (EES) is a rare soft tissue tumor predominantly observed in adolescents and young adults, and is characterized by aggressive behavior. So far, only two cases of primary axillary soft tissue EES have been reported in the literature. One of them was a 29-year-old female patient who presented with a lump in her left axilla. Upon examination, an irregular, painless mass, measuring 5 cm × 5 cm × 3 cm, was noted in the left axilla. A histopathological examination of the mass revealed small, round, blue cells with scant cytoplasm, round nuclei, numerous mitosis, and necrosis. An immunohistochemistry (IHC) examination was positive for CD99 and negative for ER, PR, Her2neu, CK7, CK5/6, CD56, CD45, CK-pan, CKHMW, P63, desmin, S100, TdT, vimentin, myogenin, synaptophysin, and chromogranin A. The patient was diagnosed with primary axillary soft tissue EES and was started on neoadjuvant chemotherapy. Twelve months later, she is clinically free from the disease.

OBJECTIVE: Epithelioid rhabdomyosarcoma (EpiRMS) is a novel morphologically distinct variant of rhabdomyosarcoma, with an unusually challenging microscopic diagnosis. The occurrence of rhabdomyosarcomas in the jaws is extremely rare. This study presents the first case of EpiRMS in the jaw (mandible) and a literature review of the previous 35 cases of EpiRMS.
METHODS: Here, we report a case of EpiRMS affecting an 18-year-old male patient. Clinical, imaging, microscopic, and immunohistochemical features are discussed and previously reported cases of EpiRMS are reviewed.
RESULTS: An 18-year-old male patient presented with an exophytic sessile growth on the buccal gingiva, and orthopantomography revealed irregular bone loss. Microscopic analysis showed a large number of cells with epithelioid appearance. Immunohistochemistry staining was positive for desmin, myogenin, MyoD1, smooth muscle actin, h-caldesmon, INI-1, and AE1-AE3. The patient\'s disease was staged as T4aN1M0 and was treated with surgical excision combined with chemotherapy.
CONCLUSIONS: The occurrence of RMS in the mandible is rare, and this is the first case of EpiRMS in the jaw. EpiRMS is an unusual histologic subtype that mimics other sarcomas and epithelial malignancies, making diagnosis a challenge. A specific immunohistochemistry panel aids in the diagnosis. EpiRMS has an aggressive course and an unfavorable prognosis.

Rhabdomyosarcoma is the most common sarcoma diagnosed in childhood and adolescence, arising from the bladder/prostate in only 5%-10% of cases. Treatment-induced cytodifferention of tumor cells into mature rhabdomyoblasts has been reported following chemoradiation and is thought to suggest a more favorable outcome. We report a case of embryonal rhabdomyosarcoma of the bladder/prostate that exhibited extensive cytodifferentiation with downregulation of myogenin and MyoD1 gene expression in rhabdomyoblasts following treatment with chemoradiation therapy. The downregulation of myogenin and MyoD1 expression in rhabdomyoblasts following chemoradiation treatment has not previously been described in the literature and its significant remains uncertain.

Primary pineal rhabdomyosarcoma (RMS) is extremely rare, and only three cases have been reported so far. Here, we report a case of 12-year-old male who presented with complaints of diplopia and diminution of vision since 15 days. He also had left-sided facial paresis. Magnetic resonance imaging brain revealed a space-occupying lesion in the region of pineal gland. The patient underwent midline suboccipital craniectomy with excision of tumor. Microscopic examination revealed a highly cellular tumor with areas showing small round cells admixed with cells having abundant eosinophilic cytoplasm resembling rhabdomyoblasts and multinucleated giant cells. Differential diagnoses of pineal anlage tumor and primary RMS were considered. The tumor cells were positive for desmin while being negative for synaptophysin and glial fibrillary acidic protein. Myogenin was used to confirm the diagnosis of RMS, which showed focal nuclear positivity. INI1 was retained. All the markers for germ cell tumors were negative.

This paper reported a case of cervical intraspinal metastasis of alveolar rhabdomyosarcoma (ARMS). The clinicopathological features, surgical treatment, chemotherapy and prognosis were introduced and the current literature was reviewed. The diagnosis, differential diagnosis, treatment, molecular features and prognosis of the disease were comprehensively analyzed to improve clinicians\' knowledge of this rare disease. The primary lesion appeared about 1 year ago which was painless mass of left hand whose size was about 2 cm×2 cm. After conservative treatment, the mass gradually enlarged and the mass was resected. Postoperative pathology revealed embryonic rhabdomyosarcoma. Postoperative chemotherapy with recombinant human endostatin, liposomal doxorubicin and ifosfamide was performed. The left neck mass was found about 3 months ago, and then the left neck mass was resected under general anesthesia. Postoperative pathological examination showed small round cell malignant tumors. Severe left upper extremity pain began about 2 weeks ago with nocturnal pain and supine pain. Non-steroidal anti-inflammatory drugs were needed to relieve pain which was accompanied by numbness and weakness of the left upper extremity. MRI showed a intraspinal tumor at C5. The left thumb and index finger were absent. Hypoesthesia, muscle atrophy and hypotonia of the left upper limb were confirmed. The muscle strength of biceps brachii and deltoid muscle of the left upper limb was grade 0, the muscle strength of extensor carpus and interphalangeal muscle was grade II, the muscle strength of intrinsic muscles of hands was grade I. The tendon reflex of the left upper limb disappeared. Intraspinal mass was removed and the pain was relieved. But there was no significant change in the muscle strength of the left upper limb. Pathological examination revealed small cell malignancies which were poorly differentiated with diffuse patchy distribution and disordered arrangement. The tumor cells had round, oval or irregular nuclei, and few cytoplasms were positive for Myogenin and MyoD1. FISH test of FOXO1 gene was positive. More than 50% of nuclei showed redgreen signal separation, and the distance between redgreen signals was larger than double diameter of the signal points, which supported ARMS. Total resection of intraspinal tumors was achieved and postoperative chemotherapy was admitted. But intraspinal disseminated metastasis occurred rapidly. ARMS was rare, aggressive tumor with poor prognosis. Subdural metastasis was rare. Correct diagnosis and classification can be made only with help of modern molecular diagnostic methods, which is effective to guide the treatment.

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Rhabdomyosarcoma (RMS) occurs rarely in adults and constitutes 2-6% of all uterine neoplasms. The authors report the case of a 26-year-old woman diagnosed with botryoid RMS that presented discordant progression results on follow up imaging and cytodifferentiation on pathologic control. This case showed that radiological evaluation could be misleading as the tumor demonstrated chemotherapy-induced differentiation without volume reduction. This case illustrates the limitations of using the imaging anatomical dimensions of sarcomas for treatment planning and highlights the potential role of functional imaging to assess the response to treatment.

Medulloblastoma (MB) with melanotic and myogenic differentiation, previously known as melanotic medullomyoblastoma, is an extremely rare histological variant of MB showing melanocytic as well as skeletal muscle differentiation. Only 10 cases of this rare tumor have been reported in the literature to date. We report this case of a 2-year-old male child who presented with a midline cerebellar mass, which on histopathological examination showed classic MB intermixed with cells containing melanin pigment, along with rhabdomyoblasts, spindle cells and occasional strap cells, which corresponded to WNT subgroup on molecular classification. The cell of origin of this MB variant is likely to be neural crest-derived stem cells which are capable of multilineage differentiation. Significant findings from previous reports and important differential diagnoses are discussed. Documentation of these tumors is important to characterize the clinical behaviour and to identify distinct genetic features, if any.