The other features noted by the outside pathologist were foamy cells (macrophages) and perivascular lymphocytes. The presence of foamy macrophages should always make one reconsider a diagnosis of primary CNS neoplasm. There are a large number of lesions which can simulate CNS neoplasms, the most common of which are infarcts and demyelinating lesions such as those seen in multiple sclerosis (1). The presence of lymphocytes favored the possibility of this lesion being an acute MS plaque. Our special stains demonstrated that there were numerous macrophages (HAM-56), and reactive astrocytosis (GFAP). The inflammatory infiltrate was primarily T-cell (UCH11) and was both diffuse and perivascular. Myelin stains (Woelke) showed loss of myelin and Bielschowsky stains demonstrated relative preservation of axons. Interestingly, a proliferation marker (MIB-1)also showed high proliferation activity within the lesion
Additional clinical information was also obtained. The patient reported a flu-like illness with body aches, diarrhea and vomiting which occurred just before she began noting "clumsiness" in her left leg. The weakness progressed to left-sided hemiparesis over a ten day period. There was also a history of visual problems in the right eye 14 years ago while she was in Germany as well as in the left eye several years ago. Both of these visual problems "healed spontaneously". We suspect that these may have been MS lesions.
Contributed by Ronald L. Hamilton, M.D.