Mixed pituitary adenoma/craniopharyngioma: clinical, morphological, immunohistochemical and ultrastructural study of a case, review of the literature, and pathogenetic and nosological considerations

Mixed pituitary adenoma/craniopharyngiomas are very rare tumors. Their pathogenesis is still unclear and it is not known whether they are collision tumors derived from independent stem cells or whether they originate from a single stem cell undergoing divergent differentiation. The latter hypothesis is supported by the close commixture between the two tumor components with transition areas that has been previously described. However, "hybrid" cells with both pituitary adenoma and craniopharyngioma features have never been described. In this paper we report a case of mixed pituitary adenoma/craniopharyngioma observed in a 75-year-old woman presenting with diplopia and slight increase of serum prolactin, who underwent endoscopic endonasal trans-sphenoidal tumor resection. Histologically, the tumor was composed of a typical pituitary silent subtype 2 ACTH cell adenoma admixed with islands of adamantinomatous craniopharyngioma. Electron microscopy showed that, in addition to distinct silent subtype 2 ACTH and craniopharyngioma cells, there were "hybrid" cells, showing characteristics of both pituitary adenoma and craniopharyngioma, consisting of small dense secretory granules, bundles of cytoplasmic filaments, and desmosomes. This ultrastructural finding was also confirmed by the presence of cells showing nuclear p40 expression and chromogranin A immunoreactivity. The close commixture between the two components and the ultrastructural and immunohistochemical findings demonstrate a common histogenesis of the two components and support the classification of the neoplasm as a mixed tumor. The patient completely recovered and, 10 months after surgery, head MR confirmed the complete resection of the lesion.

Mixed Epithelial and Stromal Tumor of the Kidney: Preliminary Immunohistochemical and Electron Microscopic Studies of the Epithelial Component

Mixed epithelial and stromal tumor of the kidney is a rare biphasic tumor composed of cysts and tubules embedded in the spindle cell stroma. Although the histogenesis of this tumor is unknown, it has been proposed that both components of the tumor, i.e., stromal and epithelial, are neoplastic. The authors report preliminary immunohistochemical and electron microscopic studies of the epithelial component from one case of a typical, benign, mixed epithelial, and stromal tumor of the kidney. In this study, some tubules showed positivity for proximal, while others showed positivity for distal, nephron immunomarkers. By electron microscopy, some tubules had features of proximal tubular epithelium, while other tubules had features of the loop of Henle (thin segments). The authors believe that in a benign tumor such morphologic heterogeneity is inconsistent with neoplastic proliferation. Therefore, they postulate that in mixed epithelial and stromal tumor of the kidney the tubules are entrapped rather than neoplastic. Additional studies are needed to address this issue and electron microscopy should play a significant role in this process.

Hyaline globule-like structures in undifferentiated sarcoma cells of malignant müllerian mixed tumor of the fallopian tube

Malignant müllerian mixed tumors (MMMTs) of the fallopian tube are very rare neoplasms, and we present such a case with unusual findings here. A 57-year-old Japanese woman, after she received a medical checkup, underwent salpingo-oophorectomy on the suspicion of ovarian cancer. At the time of operation, the main tumor was present predominantly in the fallopian tube. Microscopically, the tumor consisted of carcinoma and sarcoma components. The carcinoma showed moderately to poorly differentiated adenocarcinoma. The sarcoma consisted of predominantly undifferentiated sarcoma and focally rhabdomyosarcomatous cells with abundant eosinophilic cytoplasm. Immunohistochemically, the differentiation toward rhabdomyosarcoma was confirmed. Interestingly, the cytoplasm of undifferentiated sarcoma cells contained hyaline globule-like structures. These structures showed a positive reaction for PAS, and these structures were not digested by the diastase pretreatment. Ultrastructurally, hyaline globule-like structures corresponded to lysosomes. Finally, pathologists should keep in mind that undifferentiated sarcoma cells in MMMT of the fallopian tube may contain hyaline globule-like structures in the cytoplasm.

[Perineuriomas and other tumors with perineurial differentiation]

This is a review of the literature on the peripheral nerve sheath tumors with perineural differentiation. The authors provide an overview of the clinicopathological, immunohistochemical, ultrastructural, and genetic features of these neoplasms. Emphasis is laid on various morphological variants of perineurioma (intraneural, retifrm, sclerosing, plexiform, atypical, malignant, etc.) and so-called hybrid tumors (schwannoma-perineurioma, neurofibroma-perineurioma).

Mixed tumor of the vagina: a case report

We report a case of mixed tumor arising in the lower vaginal wall. The patient was a 20-yr-old nullipararous woman. The tumor was relatively well-defined with expansile margin, and showed solid sheets or fascicles of stromal-type spindle cells and ovoid epithelial cells with sparsely scattered nests of mature squamous epithelium and glands lined by mucinous epithelium. Cellular atypia was not conspicuous, however, mitosis was counted upto 6 per 10 high power fields. We examined this tumor immunohistochemically and ultrastructurally and reviewed the articles to identify the histogenesis. Positive reaction for vimenin and cytokeratin of stromaltype spindle cells and presence of desmosome-like structures and tonofilaments on electron microscopic examination suggested the epithelial origin of the stromaltype spindle cells.

Apocrine gland tumor of the eyelid in a dog

A 13-year-old male Shetland Sheepdog with progressive exophthalmos had a neoplastic mass in the ocular adnexa. Histologically, this neoplasm was composed of duct-forming epithelial cells with decapitation secretion. Tumor cells invaded the globe through the tunica conjunctiva and replaced the vitreous body. The cornea, iris, ciliary body, and retina were extensively destroyed. Both the epithelial and spindle-shaped myoepithelial cells showed nuclear atypia and mitotic activity in the globe. The primary tumor was diagnosed as adenocarcinoma, probably originating from apocrine sweat glands of the eyelid, and the infiltrating intraocular neoplasm was diagnosed as a malignant mixed tumor.

[True malignant mixed tumor of the parotid gland (carcinosarcoma)]

True malignant mixed tumor (carcinosarcoma) is a rare salivary gland tumor. In contrast to malignant mixed tumor, which means carcinoma ex pleomorphic adenoma in true malignant mixed tumor both carcinomatous and sarcomatous features are present in the same tumor. This report presents the case of a 43 year old man with a carcinosarcoma of the right parotid gland. Carcinomatous component was high grade ductal carcinoma. Mesenchymal component showed the features of giant cell type malignant fibrous histiocytoma. The diagnosis was supported by positive staining for cytokeratin in the carcinomatous part and positive vimentin, alpha-1-antitrypsin and CD 68 staining in the sarcomatous part of the tumor. Ultrastructural investigation confirmed the diagnosis. Multinucleated osteoclast type giant cells are probably of reactive origin.