Ribosome-lamella complex in aggressive solitary fibrous tumour of the meninges

Abstract

Approximately 60 cases of solitary fibrous tumour (SFT) have been reported in the meninges [6]. Only a few cases have been malignant with local recurrences being the most common manifestation [2, 4, 6]. We report the biopsy and autopsy findings of a malignant SFT demonstrating multiple intracranial recurrences over a 17-year period, meningeal spread and invasion into brain tissue. The presence of ribosomelamella complexes (RLC) in an SFT is described for the first time. In 1985 a 59-year-old man presented with dizziness. A left-sided tentorial tumour compressing the cerebellum was completely removed. A recurrent tumour was subjected to surgery 13 years later. The patient died from acute myocardial infarction in 2002, 4 days after surgical resection of a leptomeningeal tumour compressing the cervical portion of the spinal cord (C7 level). Samples from the three tumours removed over the 17year period were fixed and embedded in paraffin wax according to our routine protocol. In addition to routine stainings, immunohistochemical analyses were performed using primary antibodies against the following epitopes: CD34 (Novocastra Laboratories, Newcastle upon Tyne, UK), bcl-2 (Novocastra), desmin (Dako, Glostrup, Denmark), epithelial membrane antigen (EMA, Novocastra), S-100 (Dako), muscle actin (Dako) and Ki67 (Dako). The use of McDowell’s fixative precluded successful Ki67 immunostaining of the oldest biopsy specimen. Electron microscopic examination was performed in all cases. The histological appearances of the three surgical samples were almost identical. The tumours were composed of elongated cells arranged in fascicles between prominent eosinophilic bands of collagen (Fig. 1). No whorls, psammoma bodies, or necroses were observed. Mitoses were absent in the original tumour, whereas the first tentorial recurrence in 1998 demonstrated seven, and the intraspinal tumour from 2002 ten mitoses per ten high-power fields. Immunohistochemical analyses demonstrated strong and uniform expression of CD34 and bcl-2. Scattered cells were positive for desmin. All samples were negative for EMA, S-100 and muscle actin. Approximately 5% of the cells in the recurrence from 1998, and 10% of the cells in the intraspinal tumour from 2002, expressed Ki67. Electron microscopic examination of the tumours from 1998 and 2002 showed cells without basal laminas connected by desmosome-like structures and surrounded by collagen fibres. Interdigitating cytoplasmic processes, typical of meningiomas, were not observed. The cytoplasm of the spindle-shaped tumour cells contained prominent rough endoplasmic reticulum (RER) arranged in concentric, multilaminar structures consistent with RLCs (Fig. 2). The RLCs were numerous and found in more than 50% of the tumour cells. Similar structures were not observed in the original tumour. Autopsy findings demonstrated four tumours in the posterior fossa; a small recurrence of the left-sided tentorial tumour (diameter 0.8 cm) and three leptomeningeal tumours (2.1, 2.0 and 0.3 cm, respectively) outside the original operation field. Two of the latter compressed the brain stem (Fig. 3). A darker area inside the left inferior colliculus was noted. The histopathological findings in all tumours diagnosed at autopsy were identical to those in the surgical specimens described above. Microscopy of the darker area of the left inferior colliculus showed an identical tumour within the brain tissue (Fig. 4). Mitoses were not observed in any tumour. The Ki67-index was less than 1%, but the other immunohistochemical findings were D. Scheie (&) AE F. P. Reinholt AE K. Skullerud Department of Pathology, Rikshospitalet-Radiumhospitalet HF, 0027 Oslo, Norway E-mail: david.scheie@rikshospitalet.no