Quiz 60: What is your diagnosis?

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Diagnosis: Quiz 60

Quiz 60

Answer:  Neuroendocrine carcinoma

Criteria for diagnosis clinically: A shiny, cayenne-pepper-colored nodule is consonant with neuroendocrine carcinoma.

Differential diagnosis clinically: This could be one of a variety of epithelial or nonepithelial neoplasms likely malignant and biopsy is crucial to establishing a diagnosis with surety.

Criteria for diagnosis histopathologically: An asymmetrical nodule of neoplastic cells that extends from just beneath the thinned surface epidermis far into the subcutaneous fat and made up of cells with large, roundish, stippled nuclei punctuated often by clumps of chromatin and displaying little discernible cytoplasm, many of the cells being necrotic and many in mitosis, is a neuroendocrine carcinoma.

Differential diagnosis histopathologically: There really is none. These are not the findings typical of a metastasis of oat-cell carcinoma from a lung.

Clinicopathologic correlation: The nodule is formed by the sheet of neoplastic cells, the red hue is the result of venules throughout the neoplasm having, in vivo, been dilated widely and replete with erythrocytes, and the surface is smooth and shiny because the cornified layer is orthokeratotic compactly.

Options for therapy predicated on knowledge of histopathologic findings: Neuroendocrine carcinoma, especially one that involves the subcutaneous fat, is given to metastasize and, therefore, complete excision as soon as possible after diagnosis has been established is mandatory. The fate of a patient such as this one, however, was sealed by virtue of the neoplasm having already metastasized.

1) What is now termed neuroendocrine carcinoma was first described by Toker as "trabecular carcinoma." That general pathologist did not appreciate, however, that the neoplastic cells might be related in some way to normal Merkel cells. When that reality was recognized, the neoplasm became known as "Merkel-cell carcinoma," and, when later it came to be understood that the cells constituent were not simply analogues of Merkel cells, the condition then was designated neuroendocrine carcinoma.

2) The features clinical of this neuroendocrine carcinoma are typical of it, but even so, a diagnosis with certainty cannot be made on the basis of examination gross alone. Biopsy is requisite to coming to a diagnosis of neuroendocrine carcinoma with utter confidence. The findings histopathologic shown here are definitive for and stereotypical of it, to wit, a nodule made up of a sheet of cells whose round nuclei are stippled rivetingly and many of which are necrotic or in mitosis.

3) Should there be any doubt about the diagnosis histopathologic of neuroendocrine carcinoma in skin after sections of tissue stained routinely by hematoxylin and eosin have been studied (e.g., the possibility of the neoplasm being an oat-cell carcinoma of the lung metastatic to skin), cytokeratin 20 reveals consistently in a neuroendocrine carcinoma a paranuclear dot, which is both sensitive and specific for it.

4) Recently, in the January 17 issue of Science for 2008, Feng and coworkers reported on finding a polyomavirus in "human Merkel cell carcinoma," they believing it to be the agent causative. For that judgment to be sustained requires confirmation by others.

5) Kaposi's sarcoma, bowenoid papulosis, and the squamous-cell carcinoma that follows on epidermodysplasia verruciformis have been shown to be induced by a virus, so that well may be the case, too, for neuroendocrine carcinoma. Inevitable it is that other hyperplasias and neoplasias, benign and malignant, will be proven to be viral in cause.

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