Primary cerebral rhabdomyosarcoma (PCR) is extremely rare and occurs almost exclusively in the pediatric age group.1,3–5,7,8
To the best of our knowledge, only 9 cases (including our patient) of adult PCR were described in the English-speaking literature,1,4–6,9–12
and for some authors it represents a distinct entity. In adult cases patient ages ranged from 24 to 68 years (mean 47.1 years) without a gender predilection (4 males and 5 females). While in the pediatric population PCR is mainly situated in the infratentorial compartment, in adults there is a tendency to supratentorial localization (7 out of 9 cases) ().
Clinical summary of previously reported cases of primary cerebral rhabdomyosarcoma in adult population (English literature).
This tumor has no distinguishing imaging features from other primary or secondary malignant brain neoplasms.1
The typical MRI appearance is that of a iso-hypointense lesion on T1-weighted images and hyperintense on T2-weighted images, most commonly with poorly defined margins and an intense but heterogeneous enhancement after Gadolinium administration. Sometimes this neoplasm may have a cystic component (as in our case) and/or an hemorrhagic presentation. Differential diagnosis should include high-grade glioma, lymphoma, metastases and PNET. Histological confirmation is essential for the definitive diagnosis.1,4–6,9
Rhabdomyosarcomas constitute a unique group of soft tissue neoplasms that share a propensity to undergo myogenesis, a well-defined biologic process that primarily occurs during embryonal and fetal development. The most diffuse pathological classification identifies four subtypes: embryonal, alveolar, botyroid and pleomorphic.3
A primary involvement of the brain has to be differentiated from an intracranial extension from skull or para-menigeal sites (orbit, nasopharynx, paranasal sinuses, middle ear, external auditory canal), but also from a metastatic seeding from a systemic rhabdomyosarcoma and from mixed primary cerebral tumors of the central nervous system in which rhabdomyoblastic areas are found in combination with sarcomatous, neuroectodermal, mesenchimal or teratomatous features.1
PCR consists primarily of small cells that show little or no specific differentiation at the hematoxylin-eosin level. Thus, immunohistochemistry and/or electron microscopy are necessary for diagnosis, particularly immunostains for desmin and myogenin.3,7,8
Histologically, PCR must be differentiated from other brain tumors that occasionally show skeletal muscle elements, such as medullomyoblastomas, gliosarcomas, germ cell tumors and even rare meningiomas. Histogenesis of this rare mesodermal tumour is still matter of debate. Some Authors concluded that it arises from pluripotential cells misplaced during embryonic life. An origin from primitive neural crest cells that have undergone mesoectodermal differentiation is also considered a possibility. These undifferentiated mesenchymal cells are normally described in pericapillary locations, particularly in the pia mater.1,3–7)
The aim of treatment should be gross-total surgical resection, followed by radiotherapy and/or chemotherapy, both in pediatric and adult PCRs. As for our case, we achieved a macroscopically complete surgical removal of the lesion, as confirmed by post-operative MRI. In the vast majority of cases radiation therapy is the adjuvant treatment of choice, with a total dose and fractionation similar to what is used for malignant gliomas. In fact, for our patient a total dose of 60 Gy in 30 fractions was administered. There is no consensus regarding the role, or type, of chemotherapy. Relatively good results were reported after the administration of VAC (vincristine, actinomycin D and cyclophosphamide) or ICE (ifosfamide, carboplatin and etoposide). Despite modern surgical techniques and adjuvant oncological treatments, PCR is associated with an extremely poor prognosis, as reported in the Literature, where survival is almost always less than 12 months with only few patients alive after 24 months.1,4–6,9–12