Infectious lesions mimicking central nervous system neoplasms

Infections of the central nervous system (CNS) presenting as space-occupying lesions are not uncommon, particularly in developing countries. Most often, infective organisms gain entry into the CNS through the hematogenous route, seed the parenchyma, and cause tissue destruction. Subsequently, some form mass lesions in a manner similar to neoplastic growths. The commonality in pathogenesis and pathology between infective agents and neoplastic cells underlies the similarities in their presentations. Although neoplasms are the common considerations in the presence of enhancing lesions with perilesional edema and mass effect on neuroimaging, nonneoplastic conditions-in particular, infectious lesions--can have similar imaging characteristics. The widening spectrum of opportunistic and newly recognized pathogens has added to the difficulties. Biopsy diagnosis is mandatory for neoplasms, both for confirmation of diagnosis as well as grading, but most infectious lesions are managed conservatively if the diagnosis is established by noninvasive means. This review discusses some of the common infectious lesions that mimic CNS neoplasms, with emphasis on pyogenic, tuberculous, and fungal lesions as well as parasitic and viral infections that present as intracranial space-occupying lesions. The data of infective lesions that mimicked intracranial neoplasms, from our institute, over the last 5 years, are also presented. Awareness of the pathogenetic basis of tissue injury and host response, resulting in the spectrum of clinical and imaging patterns as well as a high index of clinical suspicion, are essential for accurate diagnosis, to ensure appropriate management.