To analyse the various intracranial metastasis based on the number, location, the source (primary malignancy) and categorising the site specific metastasis based on primary malignancy.

Intracranial metastasis is the most common brain SOL, commonly from lung, melanoma and others. However, data on the source of primary tumour based on intracranial location is sparse. 

Patients diagnosed with intracranial secondaries using 18F-Fluorodeoxyglucose Positron Emission Tomography (FDG PET) scan were analysed for the number, location and the source of its origin. The predilection of different regions of the brain from different primary sites were analysed.

160 patients (62 males, 98 females) were analysed amounting to 255 metastatic lesions. 75 and 85 patients had solitary and multi centric lesions respectively. The primary malignancies contributing to the intracranial metastasis include lung(46.25%), breast (31.87%), ovary(4.37%), prostate(2.5%) and others(15.01%) . The most common primary malignancies that metastasise to the frontal, parietal, occipital, cerebellar, thalamus and brainstem regions are carcinoma of lung (n=99) followed by the breast (n=73) and that metastasise to the temporal lobe are carcinoma breast (n=10), lungs(n=8), cervix(n=2), to the corpus callosum are colon(n=1) and breast cancer(n=1), to the gangliocapsular region are breast(n=2) and endometrial cancer(n=2), to the suprasellar region are ovary(n=1) and lung cancer(n=1).

The most common primary tumours that metastasize to the brain include carcinoma lung followed by breast. This algorithm would give a clue to narrow down the search towards the appropriate primary site in those with unknown origin and in resource limited setting.