Peripheral spindled carcinoid tumor: a review of its ultrastructure, differential diagnosis, and biologic behavior

Clinical and Pathologic Characteristics of Pulmonary Carcinoid Tumors in Central and Peripheral Locations

Pulmonary carcinoid tumors occur in both central and peripheral locations, and some differences in clinico-pathological features have long been observed. We investigated a large number of resected carcinoid tumors with the aim to further define the characteristics of tumors from both locations. One hundred sixty-six resected carcinoid tumors of the lung were analyzed for a variety of clinical and pathologic features, including histology subtype, mitotic rate, Ki67 index, necrosis, invasive pattern, architectural pattern, cell morphology, sustentacular cells, neuroendocrine hyperplasia, and orthopedia homeobox protein (OTP) and TTF-1 immunohistochemical expressions. Unsupervised hierarchical cluster analysis suggested three clusters as the best solution using TTF-1 and OTP expression: TTF-1-positive and OTP-positive tumors as cluster 1, TTF-1-positive but OTP-negative as cluster 2, and TTF-1-negative and OTP-negative as cluster 3. Cluster 1 was characterized by peripheral location, presence of spindle cell component, presence of sustentacular cells, female predominance, and strong association with neuroendocrine hyperplasia. Cluster 2 was characterized by central location, polygonal cell morphology, acinar growth pattern in a subset of tumors, and only rare association with neuroendocrine hyperplasia. Cluster 3 consisted of more aggressive tumors with more heterogeneous pathologic features. Tumors showed polygonal cell morphology and acinar growth pattern. Occurrence of neuroendocrine hyperplasia was exceptional. Our study confirmed distinct characteristics of central and peripheral type carcinoid. An important difference was a strong association of the peripheral tumor with neuroendocrine hyperplasia while such an association in central tumors was negligible. The tumor location might be relevant for pathobiology of lung carcinoid tumors.

Clinicopathological and immunohistochemical analysis of spindle-cell carcinoid tumour of the lung

AIMS

To analyse the clinicopathological features and immunohistchemical profile of spindle-cell carcinoid tumours (SCCT) of the lung.

METHODS AND RESULTS

Using a cut-off value of ≥ 50% spindle cells for defining SCCT, 13 were indentified among 80 consecutively resected carcinoid cases. SCCTs are asymptomatic and are peripherally located, well-demarcated tumours. Tumour cells were composed of elongated spindle cells, with scant to moderate amounts of cytoplasm and uniform nuclei with fine granular chromatin. Immunohistochemical analysis revealed that all 13 cases were positive for three neuroendocrine markers (chromogranin A, synaptophysin and CD56). Four tumours (30.7%) were positive for broad-spectrum cytokeratin (CK) and nine tumours (69.2%) were positive for thyroid transcription factor 1. All epithelial components were negative for vimentin, but 12 tumours (92.3%) were positive for stellate-shaped cells (so-called sustentacular cells).

CONCLUSIONS

SCCTs are clinically asymptomatic, peripherally located, well-demarcated tumours, and patients with SCCTs have a favourable outcome. The immunoreactivity pattern of SCCT (low reactivity of broad-spectrum CK and reactivity for vimentin in intratumoral sustentacular cells) might result in a misdiagnosis of SCCT as mesenchymal tumour; therefore, pathologists need to be familiar with this pattern.

Well-Differentiated Neuroendocrine Carcinomas: The Spectrum of Histologic Subtypes and Various Clinical Behaviors

The term "well-differentiated neuroendocrine carcinoma" was coined to describe a variety of demonstrably neuroendocrine tumors which were more aggressive (both with respect to their histologic appearance and their clinical course) than (typical) bronchial carcinoids but were also clearly distinguishable from small cell neuroendocrine carcinomas. This umbrella term encompasses a variety of tumors previously described by a variety of terms including "atypical" carcinoids, "malignant tumorlets," peripheral stage I small-cell carcinoma, as well as neoplasms described simply as "undifferentiated carcinoma" (prior to the recognition of their neuroendocrine properties). As such, this term is a broad term and is not simply synonymous with "atypical carcinoid." Over time, at least 3 subtypes have been identified based upon their histologic appearance and mitotic index, with correspondingly aggressive clinical courses.

Pulmonary atypical carcinoid tumor with marked alphafetoprotein production and features of an adenocarcinoma differentiation

A 67-year-old man presented with a pulmonary atypical carcinoid tumor with marked elevation of the serum alpha-fetoprotein (AFP) level to 181,000 ng/ml and no hepatic metastases. Immunohistochemistry revealed AFP-positive fine granules, sparsely distributed in some cells. The proportion of the concanavalin A nonbinding subfraction was 33.7%. Light microscopy revealed hyaline globules within or outside the clear and reticular cytoplasm of a few cells. These were ultrastructurally electron-dense materials similar to the hyaline bodies observed in yolk sac tumors. The Grimelius silver method stained only a few cells and very few cells showed a positive Masson-Fontana reaction. Electron microscopy revealed secretory granules measuring 220 nm on the average in scattered cells. Immunohistochemical studies showed 5-hydroxytryptophan in many cells and 5-hydroxytriptamine or serotonin in only a few cells. As for polypeptide hormones, gastrin was detected and in autopsy specimens carcinoembryonic antigen (CEA) immunoreactive cells were observed. Past case reports on the coexistence of carcinoid tumors and adenocarcinomas in the digestive tract suggest that the tumor cells in our case are also derived from primitive or stem cells of endodermal origin and expressed unusual differentiation in the course of treatment.

Well differentiated and small cell neuroendocrine carcinomas of the lung. Two related but distinct clinicopathologic entities

Twenty-two resected pulmonary well differentiated neuroendocrine carcinomas (WDNC) were re-evaluated histologically as were 28 resected intermediate-small cell neuroendocrine carcinomas (IC-SCNC). WDNC were distinguishable from IC-SCNC by their consistently recognizable organoid architecture, and by the absence or limited extent of necrosis. Furthermore, WDNC could be subclassified into 3 subsets based upon the degrees of pleomorphism, local and vascular invasion, and stromal fibrosis, the mitotic count, and the extent of tumor necrosis. Whereas all those parameters were important in discriminating between WDNC and IC-SCNC, the quality of the organoid architecture, and the extent and pattern of necrosis emerged as the most significant. WDNC with the more aggressive histologic features (subset III) had, as a group, a distinctly worse clinical course that those displaying blander features (subsets I and II). Nevertheless, even subset III of WDNC had, as a group, a longer survival than similarly treated Stages I and II IC-SCNC. We conclude that the histologic spectrum of WDNC is broader than generally recognized. Moreover, 3 subsets of WDNC are definable based on conventional histologic criteria provided sufficient, well preserved samples are examined. Even the most aggressive subset of WDNC can be thus histologically discriminated from IC-SCNC, and, given comparable stages, has a better prognosis than the latter.

Bronchial carcinoid with multiple aerogenous implanted foci

A case of bronchial carcinoid with intrapulmonary dissemination was demonstrated. A right upper lobectomy was performed because of an abnormal shadow in the lung detected by an X-ray mass survey. A carcinoid tumor originated from the spur region of the right upper lobe bronchus. The tumor protruded into the bronchial lumen and also extensively expanded into the surrounding alveolar tissue. The tumor showed typical histological features of bronchial carcinoid with a mixed insular, trabecular, and glandular pattern. Multiple implanted foci of tumor cells were found in the periphery of the lobe. The implanted tumor cells replaced the alveolar epithelium without destruction of the alveolar structure, which suggests the possibility of aergenous spread of bronchial carcinoid. This is the first report on bronchial carcinoid with aerogenous spread.

Tumors of the diffuse endocrine system, histochemical and electron-optic aids, and pitfalls in diagnosis

Tumors of the Diffuse Endocrine System are a heterogeneous group of malignant neoplasms which have rather characteristic light microscopic and cytologic features. These are, however, not diagnostic and their identification with separation from non-neuroendocrine carcinomas require important adjunctive evaluations including histochemical analysis, immunocytochemical characterization and electron-optic identification of endocrine secretory products and paracrine effects in the cytoplasm of the neoplastic cells. The importance of proper classification cannot be over-emphasized because of the often considerable biologic and prognostic differences between neuroendocrine carcinomas and other types of carcinoma, notably metastatic carcinomas from the breast and the prostate. Furthermore, the separation of these lesions into two groups; a small cell type and those with large cells (carcinoid type) appears to have clinical significance in both diagnosis and response to therapy.

Peripheral lung carcinoid tumor producing predominantly gastrin-releasing peptide (GRP). Morphologic and hormonal studies

A carcinoid tumor of the peripheral lung producing gastrin-releasing peptide (GRP), a peptide hormone known to be present in the endocrine cells of fetal bronchial epithelium, is reported. Brain-gut peptide hormones in this tumor were assayed by radioimmunoassays, localized by immunohistochemistry and characterized by gel filtration. Electron microscopic study revealed that tumor cells resembled P-cells of normal human fetal bronchial epithelium. While GRP-containing cells were predominant in this tumor, calcitonin-containing cells were also found in some areas. Difference in distribution of hormones according to histologic features was noted in the tumor. A greater portion of the tumor showed spindled cells that predominantly contained GRP, and a smaller portion of the tumor showed cells arranged in tubular or trabecular patterns that mainly contained calcitonin. The gel-filtration pattern of the tumor extracts consisted of two peaks, one of these corresponded to the synthetic replicate of porcine GRP, and another was considered to correspond to C-terminal fragments of the peptide.

Ultrastructural and Immunological methods in diagnostic pathology in a community hospital

Five unusual tumors and one case of glomerulonephritis were examined by light microscopy, immunochemical methods, and electron microscopy in order to arrive at a correct diagnosis. We propose that these techniques can be used in community hospitals for selected cases in order to classify certain types of tumors, identify the primary site of some metastatic tumors, and help in the precise classification of some autoimmune diseases.