Bruce Mackay

Granular Cell Tumor: A Review of the Pathology and Histogenesis

As the name suggests, the histogenesis of the granular cell tumor is uncertain, but this intriguing neoplasm has occasioned much speculation and controversy since its description in 1926 as a myoblastoma. Though ubiquitous in its anatomic location, it is usually small, solitary, benign, and readily recognized by routine light microscopy, and questions concerning it are principally academic. However, a small number of cases are malignant and they can be difficult to identify in paraffin sections. The combined input from immunohistochemistry and electron microscopy has greatly clarified understanding of the morphology of this lesion and both methods are helpful when the differential diagnosis is a problem. The cell of origin is still undecided, and although distinct neural features argue for Schwannian origin, the noncommittal term granular cell tumor continues to be appropriate.

Salivary duct adenocarcinoma: a high grade malignancy.

Salivary duct carcinomas of the major salivary glands have two major distinguishing features. They closely resemble ductal carcinomas of the breast and they are high-grade malignancies. In general, but particularly for carcinomas measuring three or more centimeters in size, the clinical course is one characterized by a resistance to local control, metastases to regional lymph nodes and distant sites, and death within a few years after primary surgical treatment.

Bleomycin Hypersensitivity Pneumonitis

Three patients developed radiologic and functional pulmonary changes after bleomycin therapy similar to ones previously associated with administration of this drug. However, biopsy specimens showed a pattern consistent with hypersensitivity pneumonitis rather than the interstitial pneumonia usually reported in bleomycin pulmonary toxicity. There was a patchy eosinophilic infiltrate surrounding small airways and distal air spaces, but no immune deposits were noted by ultrastructure or immunofluorescence using conventional techniques and a specific antibody against bleomycin. Two of the patients had peripheral eosinophilia of 12% and 16%. All three patients showed considerable improvement on chest roentgenogram after corticosteroid treatment. Our findings are consistant with the view that bleomycin hypersensitivity pneumonitis has a different pathogenesis than bleomycin interstitial pneumonitis. Its recognition as a separate entity seems warrnated because of the favorable response to steroid therapy.

Ultrastructure of pulmonary bleomycin toxicity

Three cancer patients developed pulmonary distress during treatment with bieomycin. Light microscopic examination of lung tissue obtained by percutaneous biopsy revealed a diffuse alveolar damage progressing to interstitial pneumonitis. With electron microscopy, interstitial adema and collagen deposition, accumulation of fibroblasts, disappearance of type I, and proliferation of type II alveolar epithelial cells were noted. Alveoli contained proteinaceous material and a mixture of macrophages and type II cells. A peculiar alteration was noted in some type II cells consisting of shortening of the microvilli and extrusion of cytoplasmic lamellar bodies with possible surfactant impairment. These findings are consistent with the drugs effect upon the alveolar epithelium. Bleomycin, therefore, can be considered another etiologic agent of iatrogenic interstitial pneumonitis.

Oncocytic adrenal cortical carcinoma.

A case of adrenal cortical carcinoma composed of mitochondria-rich cells is reported. The cells contained condensed zones and loose whorls of smooth endoplasmic reticulum. Crystalline matrical inclusions were present in some of the mitochondria, whereas others contained round, homogeneous, dense matrical inclusions. Flow cytometry revealed a hyperdiploid stem line with a DNA index of 1.3.

The adenomatoid tumor: Fine structural evidence for a mesothelial origin

The fine structure of an adenomatoid tumor of the epididymis is described. The thin‐walled channels that characterize light microscopic preparations are lined by cells having irregular, microvillus‐like projections on their luminal surface. Adjacent cells are united by terminal bars and by elaborate series of desmosomes. Between adjacent cells, there are regions where the apposed cell membranes separate to form an anastomosing network of secondary channels which communicates with the main channel lumen and rarely with the stromal space. Round cells present within the channel lumens do not closely resemble any specific blood or connective tissue cell. It is suggested that these cells migrate from the surrounding stroma into the channel lumen where in time they disintegrate. The fine structural observations strongly support the concept of a mesothelial origin of the adenomatoid tumor.

Myoepithelioma of the palate. Report of a case with histochemical and electron microscopic observations

A case of myoepithelioma of the palate is presented. Histologically, the tumor consisted of slender, spindle‐shaped cells, arranged in closely packed interlacing bundles separated by slender sheets of collagenous stroma. Histochemical studies disclosed high levels of alkaline phosphatase and adenosine triphosphatase activity. Ultrastructurally the cells contained many slender, longitudinally‐oriented filaments approximately 60 Å in diameter. Numerous mature desmosomes were present between tumor cells. The light microscopic, histochemical, and ultrastructural features are considered compatible with the diagnosis of benign myoepithelial cell tumor.

Granular cell tumors.

The skin and subcutaneous tissue and mucosae of the head and neck are areas of predilection for granular cell tumors. These often histogenetically enigmatic lesions have two principal clinicopathologic presentations: an infantile (congenital) epulis form of the gnathic gingiva and a noncongenital soft tissue and aerodigestive form. Recurrences of either form are largely attributable to marginal excision and, for all sites, approach 15%. A malignant granular cell tumor is recognized, but requires rigorous histologic confirmation.

Malignant granular cell tumor: Immunocytochemical and ultrastructural observations

Malignant granular cell tumor is an exceedingly rare tumor and only a few cases are documented in the literature. We report a malignant granular cell tumor of the subcutaneous tissue of the thigh in a 59-year-old man, and discuss the ultrastructural and immunocytochemical findings and their diagnostic value.

The Roles of Immunohistochemistry and Electron Microscopy in Distinguishing Epithelial Mesothelioma of the Pleura from Adenocarcinoma

It is often difficult to make a firm diagnosis of mesothelioma by routine light microscopy. Most mesotheliomas are pleural and epithelial, and the problem is usually to rule out the possibility of an adenocarcinoma that has extended to the pleura from the underlying lung or a more distant source. Histochemical stains are of limited value in resolving this differential diagnosis, and the customary approach is to request a battery of immunohistochemical stains or, if tissue is available, to resort to electron microscopy. In this article, we review the abilities of the two techniques to discriminate between epithelial pleural mesothelioma and adenocarcinoma. We suggest that while there is no consistently reliable method, a carefully selected and cautiously interpreted group of immunostains will often strongly favor one or other tumor. The contribution of electron microscopy ranges from establishing a definite diagnosis in the majority of instances to offering no aid in the case of some poorly differentiated tumors.