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Dear Editor, Filariasis is common in tropical countries and is a major public health problem in India. Microfilariae have been reported in association with various neoplasms such as transitional cell carcinoma, non-Hodgkin lymphoma, Ewing's sarcoma of the bone, squamous cell carcinoma of the cervix, osteoclastoma of the femur, urinary sediment, pleural fluid and a tumour of the maxillary antrum.[1-4] However, microfilariae have only rarely been identified in intracranial neoplasms: five case have been documented, in meningioma, cerebellar haemangioblastoma,[2] diffuse fibrillary astrocytoma, anaplastic astrocytoma and craniopharyngioma.[5] We present a case in which a microfilaria that was found intraoperatively in a squash preparation of oligodendroglioma but none were found in subsequent histology; screening tests were negative. Thus, diligent examination of cytology smears is necessary for the appropriate treatment.

A 32-year-old male patient, a resident of Bihar, presented with multiple episodes of seizures and headache for the previous 3 years. The headache was holocranial, severe and associated with vomiting. There was no history of visual disturbance, loss of consciousness, fever, or any bladder or bowel symptoms. Physical examination was unremarkable. On magnetic resonance imaging (MRI), a right parietal space-occupying lesion was detected, which was hypointense on T1-weighted and hyperintense on T2-weighted imaging. Magnetic resonance spectroscopy (MRS) showed a choline peak.

The tumour was excised through a right parietal craniotomy using ultrasonic resection. Intraoperative squash smears were prepared according to a standard protocol[6] and alcohol-fixed slides were stained with toluidine blue and rapid haematoxylin and eosin (H&E) using standard protocols. The tissue was routinely processed for histopathology.

During the operation, the dura was tense and the mass lesion was encountered on the surface. Grossly, it was greyish white, soft, highly vascular with infiltrative margins. Squash smears from the tumour tissue revealed sheets of dissociated round-to-oval cells with mild nuclear atypia, speckled chromatin, indistinct nucleoli and inconspicuous cell processes. Fine branching capillaries were seen with perivascular cell aggregates. Small specks of calcification were also noted in between the tumour cells consistent with the morphology of an oligodendroglioma (Figure 1a).[6] In the cellular background of these atypical tumour nuclei, an isolated sheathed microfilaria with its tail tip free of nuclei was also noted, conforming to the morphology of Wuchereria bancrofti (Figure 1b,c). A diagnosis of oligodendroglioma with filariasis was suggested. Subsequently, histopathology confirmed the diagnosis of oligodendroglioma, WHO grade II (Figure 1d); however, on extensive search no microfilaria was noted in histopathology sections.

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Figure 1. (a–c) Squash smear cytology shows (a) sheets of dissociated round to oval cells with mild nuclear atypia, speckled chromatin and indistinct nucleoli along with fine-branching capillaries with perivascular cell aggregates: toludine blue ×200; (b) a sheathed microfilaria ([RIGHTWARDS ARROW]) in the background of oligodendroglioma along with specks of calcification: haematoxylin and eosin (H&E) ×100; (c) high power of the sheathed microfilaria of Wuchereria bancrofti: H&E × 400. (d) Histological section shows the typical appearance of oligodendroglioma with fine-branching blood vessels: H&E × 200.

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Thorough screening of peripheral blood smears did not reveal eosinophilia and three consecutive nights blood samples were also negative for microfilaria. In addition, the ICT filariasis test (ICT Diagnostics Balgowlah, New South Wales, Australia), which is an antigen test, performed on a peripheral blood sample was also negative. The patient was treated with postoperative chemotherapy for the oligodendroglioma, along with a course of antihelminthic for the tissue microfilaria. The patient was doing well when last seen on his follow-up visit 3 months after surgery.

Microfilariae of Wuchereria bancrofti have been identified in various neoplasms at different sites of the body in patients from endemic areas. According to Walter et al., the microfilariae circulating in the blood and lymphatics may migrate to ‘dead-end sites’ if there is blockage or damage of the vessels by tumour, inflammation, trauma or stasis.[5] Microfilariae may even penetrate intact blood vessels and reach the extra vascular space, thus explaining their co-existence with various neoplasms including intracranial tumours on rare occasions. It has also been suggested that an increase in the blood supply of the tumour may encourage concentration of the parasites in these sites and a subsequent haemorrhage may lead to the release of parasites into the tissue.[1] Microfilariae have been incidentally identified in various cytological samples such as aspirated material from the lymph node, thyroid, breast lump, nipple discharge, cutaneous swellings, bone marrow aspirates, bronchial aspirate, ascitic, pleural and pericardial fluid, ovarian cyst fluid and cervicovaginal smears.[1] In some of the incidentally detected cases of tissue aspirates, as in our case, microfilariae were not detected on peripheral smear microscopy;[1, 2, 5] nor was antigen testing positive in our case. However, it has been documented that tissue microfilariae can exist without microfilaraemia. In previously described cases of intracranial malignancies with incidental microfilariae, microfilaraemia was also absent in all the cases assessed for the same.[2, 5] In cases previously reported on cytological smears, no site or tumour type predilection was noted and histopathological sections subsequently revealed microfilariae in only one of these cases.[2]

To conclude, microfilariae can rarely co-exist with intracranial malignancies and meticulous search and detection of such associated incidental parasitic profiles may help in making additional therapeutic decisions necessary for the patient.

References

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