These are pictures of Poorly Differentiated Neuroendocrine Carcinoma. This is a part in the Atlas of Anatomic Pathology book
Fig. 3.93 Poorly differentiated neuroendocrine carcinoma of the large
cell type is a rare neoplasm characterized grossly by a lobulated cut
surface with focal areas of necrosis and invasion
Fig. 3.94 Poorly differentiated neuroendocrine thymic carcinoma of
the large cell type (large cell neuroendocrine carcinoma) is characterized by a vaguely neuroendocrine growth pattern composed of islands
of tumor cells with peripheral palisading of nuclei
Fig. 3.95 The cells in large cell neuroendocrine carcinoma show
enlarged nuclei with abundant cytoplasm. Foci of necrosis can be seen
(arrow)
Fig. 3.96 On higher magnification, the tumor cells in large cell neuroendocrine
carcinoma of the thymus contain enlarged nuclei with prominent nucleoli and
numerous mitoses. The diagnosis is established by the
demonstration of a positive reaction for neuroendocrine markers
Fig. 3.97 Small cell neuroendocrine carcinoma of the thymus is a
poorly differentiated type of primary thymic neuroendocrine carcinoma
that is histologically indistinguishable from small cell neuroendocrine
carcinomas from other organs. For lesions in the mediastinum, particular
care must be taken not to make a diagnosis of primary small cell
carcinoma of the thymus until a primary origin in the lung has been
properly ruled out by clinical and radiographic means. The tumor is
composed of sheets of relatively small, round blue cells
Fig. 3.98 Small cell neuroendocrine carcinoma of the thymus is characterized
by a sheetlike growth pattern. The neuroendocrine organization seen in
better-differentiated tumors is lost, and extensive irregular
areas of necrosis are seen
Fig. 3.99 A common feature of small cell neuroendocrine carcinoma
of the thymus is extensive infiltration of surrounding structures and soft
tissue. The permeative pattern of infi ltration of the mediastinal fat, with
preservation of adipocytes, is very similar to that observed in mediastinal lymphomas. Immunohistochemical stains are quite helpful for differential diagnosis,
demonstrating negative staining for lymphoid
markers and showing a positive reaction for cytokeratin and neuroendocrine markers
Fig. 3.100 In rare instances, transitions between well-differentiated or
moderately differentiated neuroendocrine carcinoma with a welldeveloped
organoid pattern and poorly differentiated, small cell neuroendocrine
carcinoma can be observed in the same tumor. In this image,
well-differentiated neuroendocrine carcinoma (left) merges with a
poorly differentiated small cell component (right)
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