Primary cerebral rhabdomyosarcoma - an oncological headache.

A 23-year-old female presented with complaints of progressive headache and vomiting of two months duration and first episode of GTCS. There was no significant medical or family history, no history of alcohol intake or substance abuse. On examination she was drowsy but responding to commands. Neurological examination revealed left sided hemiparesis with no other deficits. Blood tests after admission revealed no abnormalities. MRI imaging of brain revealed a 7.5 x 6.0 x 6.5 cm sized well-defined T1 hypo and T2 hyper-intense cystic lesion with septations in the right fronto-parietal region along with an eccentrically located enhancing solid component (Fig. 1). Correlating the clinical features and imaging findings, a working diagnosis of CNS tumor was made and she underwent maximal safe resection. Postoperative histopathology showed spindle shaped tumor cells along with cells of rhabdoid morphology. IHC was positive for GFAP, Desmin (Fig. 2), Myo D1 and negative for EMA which was suggestive of rhabdomyosarcoma which was non-meningeal in origin. MRI imaging of the head and neck, thorax, abdomen, pelvis and extremities did not reveal any other lesion. Bone scan and bone marrow biopsy and aspirate was negative for metastasis. Thereby, a final diagnosis of primary cerebral rhabdomyosarcoma (RMS) was made. Following this, she was treated with adjuvant radiation therapy to a dose of 60 Gy by the VMAT (Volumetric modulated arc therapy) technique followed by 6 cycles of chemotherapy with VAC regimen (Vincristine, Actinomycin D and Cyclophosphamide). Post chemo imaging done after 3 months was suggestive of progressive disease and patient expired 14 months after diagnosis.

Figure 1

T1 contrast MRI image shows hypointense cystic lesion with enhancing intramural nodule

Figure 2

Section shows strong positivity of the rhabdoid tumor cells for Desmin. Immunohistochemistry with DAKO primary antibody, Diaminobenzidine stain, × 400 (black arrow)

Primary Intracranial RMS are rare and mostly seen in the pediatric population, with the posterior cranial fossa being the most common location [1]. In general, it is believed that RMS arises from a population of embryonic pericapillary mesenchymal cells which persist after birth and retain the ability to differentiate along a number of pathways [2].

From a neuro-radiological point of view, RMS doesn’t have unique radiological features that differentiate it from other malignant brain tumors. The tumor usually exhibits homogenous/intermediate signal intensity with contrast enhancement on T1 and high signal intensity on T2-weighted images [2]. The rarity of primary CNS RMS does not allow a conclusive therapeutic regimen. The extent of postoperative residual disease is the most important prognostic factor and rapid recurrence after surgical resection is usual [3].

Among the adult primary cerebral RMS reported in literature with survival longer than a year, almost all cases received radiation dose of 60 Gy [2, 4, 5]. This and the clinical behavior of the tumour, akin to that of high grade glioma formed the rationale of treating the patient to a dose of 60 Gy. The chemotherapy regimen used was extrapolated from the treatment of systemic RMS where VAC based regimen is usually given for 2 years [4].

In spite of aggressive multimodality treatment the prognosis of primary CNS RMS is poor with a median survival after diagnosis of 7 months [1]. Treatment with a radiation dose of 60 Gy and the delivery of 6 cycles of triple agent chemo could have contributed to the 14-month survival seen after diagnosis in this patient.