Revisiting metastatic central nervous system tumors with unknown primary using clinicopathological findings: A single...

Metastatic tumors are the most common central nervous system (CNS) tumors wherein the primary site remains unknown in most of the cases. Aim: The study was carried out to evaluate metastatic CNS tumors with unknown primary by using simplified diagnostic (clinico-histopathologic) approach.

A 2 years study was conducted on 32 cases of CNS metastases having unknown primary tumors in a neurosciences institute.

All the results were prepared using software version of SPSS 22.

The most common metastatic site found in brain was cerebrum (59.3%) [frontal > frontoparietal > parieto-occipital > temporal] [left cerebrum > right cerebrum], followed by cerebellum (12.5%), spinal cord (9.3%), and leptomeninges (3.12%). Most of the metastatic tumors presented as ill-defined (34%) rather than well-defined (22%) lesions with ring enhancement seen only in 16% of the cases on magnetic resonance imaging (MRI).On histopathology findings with targeted immunohistochemistry, most common histological tumor type identified irrespective of site was adenocarcinoma (68.7%), followed by squamous cell carcinoma (15.6%) and poorly differentiated carcinoma (12.5%). Only one case of lymphoma was reported. Corroborating all the above findings along with clinical history and other relevant investigations, primary sites could be detected in 23 cases (71.8%).The most common primary site deduced was lungs (39.1%), followed by thyroid (17.3%), breast in females (13.0%), gastrointestinal tract (8.6%), and prostate in males (4.3%). Only in nine cases (28.1%) with mainly poorly differentiated histopathological type, primary site remained unknown.

Detection of the primary site in metastatic CNS tumors is possible by adopting this simple and effective diagnostic approach at centers/hospitals having cost and other constraints.