PM is a malignant variant of meningioma and was first described in 1938 by Cushing and Eisenhardt [3
], in which they reported a papillary pattern in a meningioma showing intracerebral recurrence and pulmonary metastasis. The main diagnostic dilemma arises in the histological diagnosis of PM. The differential diagnoses include metastatic papillary adenocarcinoma, which is epithelial membrane antigen (EMA) and cytokeratin (CK) positive but vimentin negative; papillary ependymoma, which is glial fibrillary acidic protein (GFAP) positive; astroblastoma which is characterized by a typical palisaded pattern of astrocytic cells with broad and non-tapering strongly GFAP positive processes radiating towards the central blood vessels. Other tumors like choroids plexus papilloma may sometimes cause diagnostic confusion with a PM.
In one of the largest series of PM reported, Ludwin et al [4
] described the clinicopathologic features of 17 cases and found that compared to other variants of meningiomas, PM were more frequent in children 8/17(47%). Mitoses were seen in 7/17(41%), local recurrences in 10/17(59%), brain invasion in 8/17(47%), and extracranial metastasis in 4/17(23.5%). This observation was supported by Brignolio and Favario [5
] who studied 8 cases of PM and concluded that the presence of papillary pattern in meningioma corresponds with histological and clinical aggressiveness. Similarly, Radhakrishnan et al [6
] reported 6 cases of PM all of which occurred in adults and most of them showed histological evidence of bone and brain invasion. In contrast, Stefanko and Mackay [7
] described 6 cases of PM, none of which showed either local recurrence or distant metastasis. They had suggested that these papillary structures were no more than a secondary manifestation if tumor cell vasotropism and poor cohesion between cellular perivascular 'crowns'.
PM are frequently seen in the supratentorial compartment though rare locations like posterior fossa [8
], jugular foramen [10
] and occulomotor nerve [11
] have been described. The presence of a tumor cyst is an exceptional finding in meningiomas, but it has been frequently reported in PM [12
]. The standard treatment of PM is surgical resection and the effectiveness of adjuvant radiotherapy is yet to be established. Recurrences are frequent and lung is the most favored site of extracranial metastases [14
]. The 5-year survival rate for PMs is about 40%, which is one-half for that of the other types of meningiomas [16
]. In our 15 years of experience this was the first case of PM encountered and though the tumor was adherent to the bone at the time of extirpation, no recurrence or metastasis was seen after 15 months of follow-up. The patient had normal vision and is presently completely asymptomatic.
In meningiomas of higher grade, losses of chromosome 22q and 1p have been reported apart from mutations of the NF2 gene [17
], but the genetic idiosyncrasies of PM are too scanty to be useful in making this ominous diagnosis.