| Abstract|| |
The 2007 World Health Organization classification of tumors of the central nervous system identified "pineal parenchymal tumor of intermediate differentiation" (PPTID) as a new pineal parenchymal neoplasm, located between pineocytoma and pineoblastoma as grade II or III. Because of the small number of reported cases, the classification of PPT is still a matter of controversy. We report a case of PPTID. A 25-year-old female patient was admitted to hospital with complaints of a headache, nausea, vomiting since 1-year. Computed tomography/magnetic resonance imaging of the brain showed well-defined, mildly enhancing lesion in the region of the pineal gland with areas of calcification. The tumor was excised. After 3 years, she presented with metastasis in thoracic and lumbosacral spinal region. This is a rare event.
Keywords: Differentiation, intermediate, lumbosacral, metastasis, pineoblastoma, pineocytoma, spine, thoracic
|How to cite this article:|
Patil M, Karandikar M. Pineal parenchymal tumor of intermediate differentiation. Indian J Pathol Microbiol 2015;58:540-2
| Introduction|| |
Pineal parenchymal tumors (PPTs) represent about 30% of pineal region neoplasms. PPTs are rare tumors, accounting for <0.1% of all brain tumors. They are subdivided into pineocytoma (PC), pineoblastoma (PB), and PPT of intermediate differentiation (PPTID).,, Of PPT, PCs, and PBs represent approximately 45% each, with PPTID accounting for the remaining 10%. Due to the small number of reported cases, the classification of PPT, especially PPTIDs, remains controversial., Little is known about their clinical behavior, and optimal management of these tumors has not yet been defined.,
PPTID was recognized in the 2007 World Health Organization (WHO) classification as a new pineal parenchymal neoplasm intermediate in malignancy (WHO grade II and III) between PC (Gr. I) and PB (Gr. IV). It occurs at all ages, from childhood to adult life, with a peak incidence in early adults.
Histopathologically, PPTID is located between PC and PB. PPTID are composed of diffuse sheets or large lobules of monomorphic, uniform, round cells, and characterized by moderate to high cellularity, mild to moderate nuclear atypia and low to moderate mitotic activity and occasional pineocytomatous rosettes.
In PPTIDs, the expression of neuronal markers is variable. Staining for synaptophysin is mainly diffuse, cytoplasmic, and variable in intensity. Neurofilament protein expression is variable. Chromogranin A can be especially expressed in PPTID, with a pseudostratified architecture. Glial fibrillary acidic protein and S-100 protein staining is only positive in reactive interstitial astrocytes. Ki-67 proliferation index is between 3% and 10%.
| Case Report|| |
A 25-year-old woman presented with an intermittent headache, nausea, vomiting, and giddiness since 1-year along with watery discharge from both eyes. Computed tomography/magnetic resonance imaging findings revealed a mass, enhancing in the pineal region with focal areas of calcification and diagnosed as pineal gland tumor. The patient underwent surgery with intraoperative consultation. Frozen sections stained with toluidine blue and a diagnosis of PC was offered [Figure 1] and [Figure 2]. A remaining specimen of the frozen section was sent for routine histopathology; which showed diffuse, highly cellular tumor composed of small, uniform, round cells with mild nuclear atypia. At places, the perivascular arrangement was seen. Few foci of calcification were also noted. There was no evidence of pineocytomatous rosettes or necrosis [Figure 3].
|Figure 3 : (H.P.) Sheets of small round cells with monomorphic nuclei and moderate amount of cytoplasm (H and E, ×400)|
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The final diagnosis, according to WHO criteria was PPTID (Gr. II).
After 3 years, she presented with metastasis in thoracic and lumbosacral spinal region [Figure 4] and [Figure 5] and was operated for the same in another hospital.
|Figure 4: (a) (left) Sagittal and coronal (b) (right) T1W MR image after IV administration of Gd- DTPA revealed well defined irregular heterogeneously enhancing lesion in the region of the pineal gland effacing the posterior aspect of the third ventricle and compressing the quadrigeminal plate, without causing hydrocephalus|
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|Figure 5: Sagittal gadolinium enhanced T1W MR image of thoracic spine (a) and lumbosacral spine (b) revealed multiple lesions of solid nature with cystic areas of varying sizes dispersed throughout the spinal cord, in the intramedullary and subdural space predominantly involving the thoracic spine. The solid components of these lesions showed moderate enhancement post contrast (c)|
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| Discussion|| |
A significant number of PPT do not fit accurately into the categories of PB and PC and may exhibit features intermediate between these two distinct tumors. In a recent series of cases classified according to the new WHO guidelines, PPTID accounted for 56% of the cases. This category includes tumors with histologic features, intermediate between PC and PB or tumors that have mixed areas of both PC and PB. PPTID are more aggressive than PCs and commonly present with local infiltration and distant cerebrospinal fluid (CSF) dissemination.
The morphologic features are intermediate between those of PC and PB, with a particular tendency to show lobulated grouping of unipolar tumor cells demarcated by and often aligned along a delicate vascular stroma. When the lobulated pattern occurs in the absence of pineocytomatous rosettes, these tumors are frequently associated with local invasion and dissemination along CSF pathway.
It has been suggested that a grading system based on mitotic activity and neurofilament protein immunoreactivity can distinguish low from high-grade PPTID. Recently, Jouvet et al. proposed a new prognostic grading comprising four grades: Grade I - for PC; grade IV - for PB and grade II and III for PPTID, with grade II being defined as having <6 mitotic figures/10 hpf, positive immunolabeling of neurofilament and grade III being defined as having 6 or more mitotic activity per 10 hpf or fewer than 6 mitosis but with immunolabeling for neurofilament. According to that our case would correspond to a grade II.
The rarity of PPT emphasises the importance of distinguishing these neoplasms from other neuroepithelial tumors that may impinge upon the pineal region including central neurocytoma, ependymoma, and oligodendroglioma. In contrast to central neurocytoma, PCs, and intermediate tumors demonstrated cells with better-defined cytoplasmic borders and much greater cellular pleomorphism. The intercellular matrix is less prominent, and there is a more conspicuous relationship of the cells to the fibrovascular stroma. Ependymal and oligodendroglial tumors are discerned more readily on the basis of their glial differentiation. Analysis of photoreceptor gene expression, particularly interphotoreceptor retinoid-binding protein and retinal S-antigen, may also provide an important information.
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There are no conflicts of interest.
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Dr. Meena Patil
Flat No. 8, Surya Appt., Kohinoor Colony, Sahakar Nagar No. 2, Pune - 411 009, Maharashtra
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]