A 72‐Year‐Old Male with A Slow Growing Pineal Region Tumor

Clinical History

A 72‐year‐old male initially presented in 2004 with severe headache, seizure and gait instability. A scan demonstrated a pineal space occupying lesion with hydrocephalus. An endoscopic third ventriculostomy (ETV) tumor biopsy was non‐diagnostic. He was followed clinically and radiologically for three years before he was lost to follow‐up. During the time he was followed, the lesion was asymptomatic and showed little increase in size on repeated MRI studies. Eleven years after initial treatment, he presented with three‐month history of significant gait slowing, instability and intermittent blurred vision. He developed worsening memory along with poor concentration and attention. Many of these symptoms were similar to the episode he experienced prior to his ETV. A CT scan showed a pineal region hyperdense lesion (3.7 × 3.3 × 3.6 cm) causing compression of the quadrigeminal plate with effacement of the cerebral aqueduct and quadrigeminal cistern and significant mass effect on the cerebellar vermis (Figure 1A). MRI scans showed a heterogeneously enhancing pineal region lesion causing mass effect on the midbrain, cerebellum and splenium of the corpus callosum. No hydrocephalus was noted. He underwent a subtotal resection of tumor.

Figure 1.

 

Pathology

Microscopic examination revealed small, bland appearing, spindle cells arranged in poorly delineated wavy fascicles on the collagenous background focally reminiscent of keloid (Figure 1B). The nuclei displayed minimal hyperchromasia and no mitotic activity. Slit like vessels were outlined by CD34 and CD31 immunoreactivity. Small areas with increased numbers of capillaries displayed a rich reticulin network. Larger vessels were thick walled and hyalinized. Neoplastic cells were strongly positive for Bcl‐2 (Figure 1C), CD34 (Figure 1D), CD99 and Vimentin, and negative for EMA, progesterone and estrogen receptor, S‐100 protein, desmin, smooth muscle actin, Factor 13A, GFAP and synaptophysin. There was no sign of infiltration into either the brain tissue or the pineal gland. What is your diagnosis?

Diagnosis

Solitary fibrous tumor of the pineal region.

Discussion

The majority of tumors in the pineal region are parenchymal pineal or germ cell neoplasms. SFT in the pineal region is extremely rare and only four cases have been reported in the literature to date 1, 3, 4, including an unusual example of a composite tumor of low‐grade astrocytoma with a component of anaplastic SFT 1 (Supporting Information Table 1). The main differential diagnoses of intracranial SFT are fibrous meningiomas and hemangiopericytomas (HPC).

Radiological findings of SFT are non‐specific with iso‐attenuation on CT images. MRI features are iso‐intense on T1 and iso‐intense to hypo‐intense on T2. However, with intravenous contrast administration, homogeneous or heterogeneous enhancement is reported as the most prominent feature of SFT on both CT and MRI. The dural tail sign, which is highly suggestive of meningioma, is also seen in SFT.

The distinguishing feature of SFT from both fibrous meningiomas and HPC is their uniform, Immunostains for CD34 and Bcl‐2 are strongly positive in SFT lack EMA and progesterone receptors immunostaining. Furthermore, on ultrastructural examination, SFT cells resemble fibroblasts and do not form the numerous intercellular (desmosomal) junctions typically seen in meningiomas.

SFT and HPC were previously classified as separate entities in the 2007 WHO classification of CNS tumors. However, recent molecular studies revealed NAB2‐STAT6 fusion gene and nuclear STAT6 immunoreactivity in both SFT and HPC indicating that these lesions represent a spectrum of the same tumor entity 2. SFT are usually benign and their behavior resembles that of the WHO grade I meningioma. Histologic signs of malignancy in SFT are infrequent and more often observed to be focal rather than widespread patterns. Recently different variants of the NAB2‐STAT6 fusion genes have been reported in SFT of soft tissue and have been observed to correlate with malignant histological findings (i.e., higher Ki‐67 labeling index and higher mitotic rate as well as the presence of nuclear pleomorphism and atypia) with associated biological aggressive behavior and shorter disease free survival 2. HPC, conversely, are often predictably aggressive. HPC in the pineal region is also rare and to date, only six cases have been described. Combined, only ten SFT and HPC of the pineal region have been reported (Supporting Information Table 1).

In summary, SFT of the pineal region are rare and though usually a slow growing low‐grade tumor. However, it can also exist as a more aggressive form behaving in a similar fashion to classical HPC. With recent molecular analyses, it is now possible to reclassify SFT and HPC within a spectrum of the same entity with differences in biological behavior related to histological grade of each morphological variant. In other words, each can exist in either malignant or benign forms.

Supporting information

Additional Supporting Information may be found in the online version of this article at the publisher's web‐site:

Table 1 and a complete set of sixteen references can be found at: http://path.upmc.edu/divisions/neuropath/bpath/cases/case367.html