Pineal germinomas and testicular seminoma: a comparative ultrastructural study with special references to early carcinomatous transformation

Histopathology of tumors of the pineal region

Pineal region tumors are heterogeneous lesions and include mainly pineal parenchymal tumors (PPTs), papillary tumors of the pineal region (PTPRs) and germ cell tumors (GCTs). This article describes the cystic pineal gland compared with normal tissue and histopathological features of the most frequent pineal region tumors. PPTs are subdivided into pineocytoma (grade I), pineoblastoma (grade IV) and tumors with intermediate differentiation (PPTIDs; grades II-III). A grading system based on the number of mitoses and neurofilament protein expression distinguishes low- from high-grade PPTID. PTPR is a new tumoral entity thought to originate from the subcommissural organ. GCTs include germinoma, embryonal carcinoma, teratoma, yolk sac tumor and choriocarcinoma and are often of mixed histologic composition. New histogenetic data for GCTs are presented.

Intermitochondrial cement (nuage) in a spermatocytic seminoma: comparison with classical seminoma and normal testis

The nuage, an ultrastructural marker of normal human germ cells (spermatogonia type A and primary spermatocytes), may be found associated with mitochondria (intermitochondrial cement) and/or free in the cytoplasm. Eight specimens from germ cell-related tumours were reviewed to assess whether the nuage could have diagnostic significance in testicular neoplasms. The nuage of neoplastic cells from seven classical seminomas and one spermatocytic seminoma was compared with that from two normal testes. The ultrastructural study demonstrated that only spermatocytic seminoma cells contained both types of nuage and that significantly fewer spermatocytic seminoma cells (28%) contained intermitochondrial cement compared with control spermatogonia type A (81.1%) and primary spermatocytes (47.6%). The data indicate that (1) the detection of the nuage confirms that the phenotype of spermatocytic seminoma is more differentiated than that of classical seminoma; (2) the intermitochondrial cement is an additional example of how a distinctive organelle of a normal cell is preserved in its neoplastic counterpart and (3) if the intermitochondrial cement were found in other cases of spermatocytic seminoma, this organelle of the normal germ cell lineage could be considered as a new ultrastructural marker of the neoplasm.

Pure pineal germinomas: analysis of gender incidence

OBJECTIVE

Pure pineal germinomas have been rarely reported in girls. Gender incidence and differences of pure pineal germinomas are not well known. The authors report a series of pure pineal germinoma and its gender characteristic is reviewed.

METHODS AND RESULTS

Of a total of 50 germ cell tumors operated on between 1988 and 2004 we found 26 cases (median age at diagnosis, 12 years) of pineal germ cell tumors. Of these, 14 cases (male/female ratio: 13/1) were pure pineal germinomas, and 12 cases (male/female ratio: 12/0) were non-germinoma germ cell tumors. In pure pineal germinomas, the main clinical presentations were intracranial hypertension and cranial nerve dysfunction. Imaging studies disclosed a homogeneous type of tumor (n = 10) and associated hydrocephalus (n = 6). Cases were managed with biopsy and subsequent radiation therapy and chemotherapy. After a follow up of 10 years, pure germinoma cases have no neurological deficits and tumor recurrence. The literature on gender incidence of pure pineal germinomas is analyzed and possible causes are discussed.

CONCLUSIONS

Although rare, pure pineal germinoma can be found in female subjects. On the basis of the literature review, the male/female ratio in cases of pure pineal germinoma is between 5:1 and 22:1 (mean 14:1). In our series, the male/female ratio was 13:1.

Pathology of pineal region tumors

Various histological types of tumors arise in the pineal region. The most common tumors are pineal parenchymal tumors and germ cell tumors. Pineal parenchymal tumors are divided into pineocytoma, pineal parenchymal tumor with intermediate differentiation and pineoblastoma. Pineocytomas are well-differentiated tumors and retain the morphological and immunohistochemical features of pineal parenchymal cells. Lobular architectures and pineocytomatous rosettes are also typical features. In contrast, pineoblastomas are embryonal tumors resembling primitive neuroectodermal tumors (PNET). However, pineoblastomas are distinct from PNET in other sites due to their exhibiting photosensory differentiation including Flexner-Wintersteiner rosettes and fleurettes. Although pineal cysts are tumor-like lesions, and not true neoplasms, they are occasionally difficult to distinguish from pineocytoma and astrocytoma. From the therapeutic aspect, a precise differential diagnosis is critical. The pineal region is the most common site of the brain in which germ cell tumors occur. Germinoma, teratoma, embryonal carcinoma, yolk sac tumor and choriocarcinoma are encountered, and the latter three types of tumors usually constitute elements of mixed germ cell tumors. The morphological and immunohistochemical features of intracranial germ cell tumors are very similar to those of gonadal germ cell tumors, although there are some differences in germinoma. Pineal germinoma may exhibit carcinomatous differentiation. Other types of tumors are occasionally observed, including fibrillary and pilocytic astrocytoma, glioblastoma, ependymoma, melanoma, meningioma and so on. Metastatic pineal tumors are also rare. The most common site of origin for pineal metastasis is the lung.

Germinoma in siblings: case reports

We present the first reported cases of germinoma occurring in siblings of different genders. One tumor occurred in the left basal ganglia of a 7-year-old boy and the other in the suprasellar region of his 9-year-old sister. Both tumors were diagnosed as germinoma of two-cell pattern based on light and electron microscopic studies. Possible genetic factors responsible for this phenomenon are discussed.

Pineal parenchymal tumors: an ultrastructural study with prognostic implications

The pineal gland is host to a spectrum of neoplasms. Those considered to be derived from or differentiating toward pineal parenchymal cells are rare. Traditionally, pineal parenchymal tumors (PPTs) have been divided into 3 types: pineocytomas, pineoblastomas, and mixed or transitional tumors. Their characterization has been far from adequate and no firm diagnostic criteria, light microscopic or ultrastructural, have been established. In an attempt to provide more precise prognostic diagnostic criteria, we undertook a detailed ultrastructural analysis of 17 PPTs and found them to exhibit light microscopic and ultrastructural features strikingly similar to those of pineal parenchymal cells in varying stages of development, ranging from undifferentiated primitive neuroepithelial cells to mature pineal parenchymal cells. We endorse classification of PPTs based on a combination of their light microscopic and ultrastructural features. Accordingly, PPTs can be divided into three categories: 1) pinealoblastoma, 2) PPTs of intermediate or mixed differentiation, and 3) pineocytoma, a tumor of mature-appearing pineocytes. In keeping with this classification, our 3 pinealoblastomas behaved as highly malignant tumors. A correlation of morphology and prognosis was less evident between intermediate tumors and pineocytomas, perhaps the result of considerable variation in surgical and other therapies. Evidence of neurosensory differentiation, a feature noted to a varying extent in all but the pineoblastomas, included club-shaped "nerve endings" in 7 tumors, small numbers of dense core granules in 8, clear vesicles in 7, and structures suggestive of synapses in 4. With the exception of 3 undifferentiated PPTs or pinealoblastomas lacking nerve endings, all pineocytomas exhibited some combination of these markers of neuronal specialization. In that the ultrastructural features of these PPTs were more indicative of their aggressiveness than was their degree of light microscopic differentiation or grade, we consider electron microscopy a useful adjunct, not only in diagnosis but also in therapeutic decision-making and prognostication.