Paul Strausbauch

Fine needle aspiration cytology of a mediastinal granular cell tumor with histologic confirmation and ancillary studies. A case report.

BACKGROUND Mediastinal granular cell tumors (GCT) are extraordinarily rare and have not been previously reported in the cytology literature. Fine needle aspiration (FNA) cytology of GCT resembles the cytologic features of several other lesions that are more common in the mediastinum. CASE A middle-aged female with a recent onset of nonproductive cough and otherwise unremarkable medical history presented with a mediastinal mass. Imaging studies confirmed the presence of a large mass in the superior, posterior mediastinum closely apposed to the apex of the left lung. FNA revealed scattered large, polygonal to spindle cells with granular cytoplasm and indistinct cell borders. The cytologic differential diagnosis included a benign neural tumor with granular cell features versus GCT. Histologic examination of the surgically resected mass along with supportive immunohistochemical and electron microscopic studies confirmed GCT. CONCLUSION This is the first reported case of FNA cytology of a mediastinal GCT. A reliable diagnosis can be made with aspirated material from these lesions based upon the characteristic cytologic, immunocytochemical and ultrastructural features of the tumors.

Desmosomes and Microvilli Mean a Lot: Diagnosis of Neoplasms of Unknown Origin Using Electron Microscopy

Neoplasms of unknown origin present a difficult diagnostic dilemma, particularly if they are very poorly differentiated. Adenocarcinomas, squamous cell carcinomas, melanomas, lymphomas, and sarcomas can all be very difficult to diagnose if the light microscopic cytomorphology is sufficiently undifferentiated. Electron microscopy (EM) can either demonstrate differentiation or narrow the range of differential diagnoses. The authors report the case of a 64-year-old male who has been HIV positive for several years and was found to have expansile lytic lesions in several ribs and a thumb fracture associated with a soft tissue mass which was biopsied. The tumor was composed of very pleomorphic malignant cells without specific differentiation. The malignant cells stained positive for pancytokeratin (AE 1/3), EMA, CEA, CK20, and CK7. Rare cells had mucicarmine-positive intracytoplasmic droplets. They were negative for S-100, calretinin, CD45, MART-1, and vimentin. EM revealed intracytoplasmic lumina with long microvilli and many well-formed desmosomal junctions. The diagnosis was initially very broad. Immunohistochemistry narrowed the diagnosis to carcinoma, but EM alone was able to narrow the diagnosis to poorly differentiated adenocarcinoma. In a neoplasm of unknown origin, EM can either narrow the differential significantly or, in the case of limited material, provide information that otherwise may not be attainable.

Hurthle cell adenoma of the mediastinum: intraoperative cytology and differential diagnosis with correlative gross, histology, and ancillary studies.

A 66‐year‐old man was found to have a 7.5 cm mediastinal mass detected on routine chest X‐rays as part of his preoperative work up for an inguinal hernia repair. An orthotopic (normally located) nongoitrous thyroid gland without evidence of connection to the mediastinal mass was also identified. The clinical differential diagnoses included lymphoma, thymoma, and germ cell tumor. Fine‐needle aspiration (FNA) biopsy smears and touch imprints of the mediastinal mass showed a loosely cohesive, highly cellular population of relatively uniform cells with abundant granular cytoplasm, low nuclear to cytoplasmic (N/C) ratios, and prominent nucleoli consistent with a Hurthle cell (HC) neoplasm. Subsequently, the diagnosis of HC adenoma was confirmed on the surgically excised mediastinal mass. To the best of our knowledge, the surgical pathology and cytologic features of an HC adenoma of the mediastinum have not been reported in the literature. The gross, histologic, immunohistochemical, and electron microscopic (EM) findings, in addition to the cytologic features, are presented along with a differential diagnosis of this mediastinal neoplasm. Diagn. Cytopathol. 2000;22:16–20.

Three-dimensional reconstruction of anomalous beige mouse macrophage lysosomes

Cells of the beige mouse, the murine counterpart of the Chediak‐Higashi Syndrome, contain enlarged anomalous lysosomes. The three‐dimensional structure of these lysosomes from peritoneal macrophage was ascertained by study of electron micrographs taken in a series of serial sections combined with computer‐assisted analysis. The most common basic structural units identified were biconcave discs and hollow cup/ovoid‐shaped structures. Other more bizarre forms were represented by the fusion of these basic lysosomal variants. Anomalous lysosomal forms were found in both beige resident and exudate peritoneal macrophage. A similar study of lysosomes in animals not carrying the beige mutation revealed the presence of smaller but structurally similar forms of the basic lysosomal variants. This latter finding indicates that the presence of lysosomal variants per se in the beige animal is not a finding unique to these animals but rather that their distinctiveness derives from their increased size and propensity to undergo fusion with each other. The usefulness of computer‐assisted three‐dimensional reconstruction is demonstrated.

Qualitative and quantitative differences between resident peritoneal mononuclear phagocytes of beige and control mice.

A qualitative and quantitative comparison of resident peritoneal macrophages (RPM) from beige (C57BL6Jbg/bg), (bg), and control black (C57BL/6J), (BL), mice has been made. Giant anomalous lysosomes as described for other leukocytes are inconsistently demonstrable. The principal morphological expression of the bg phenotype in RPM is the presence of elongated dumbbell‐shaped, horseshoe‐shaped, and ring‐formed cytoplasmic lysosomes demonstrable by electron microscopy. Detailed analysis indicates that these are probably variations of the same basic structure, a deformed biconcave disc with differences in form resulting from their being cut in various planes of section. Additional structural complexity results from fusion between adjacent lysosomes. Thus the distinctive lysosomes of bg mouse RPM are not totally analogous to those structures described in other cell types.