Large-cell undifferentiated carcinoma

Pleomorphic carcinoma, as defined by Fishback and associates,is a neoplasm that occurs predominantly in older patients and is composed predominantly of spindle cells and large pleomorphic giant cells. In 78 cases, the authors found foci of squamous differentiation in 8% of cases, large cell undifferentiated carcinoma in 25% of cases, and adenocarcinoma in 45% of cases. The remaining 22% of the neoplasms were composed of neoplastic... 

Lymphoepithelioma-like carcinoma, a subtype of primary large cell undifferentiated carcinoma, may occur as a primary lung cancer composed of large anaplastic cells and be confused with lymphomas and other neo-plasms.222 Most express low and high molecular weight... 

A. Zero of 10 squamous carcinomas, 4 of 26 adenocarcinomas, and 0 of 11 large cell undifferentiated carcinomas showed immunostaining for Leu7. Six of 10 squamous carcinomas, 15 of 26 adenocarcinomas, and 7 of 11 large cell undifferentiated carcinomas showed immunostaining for neuron-specific enolase. Six of 10 squamous carcinomas, 16 of 26 adenocarcinomas, and 7 of 11 large cell undifferentiated carcinomas showed immunostaining for synaptophysin. Overall, 34 of 47 (79%) carcinomas without neuroendocrine features expressed at least one neuroendocrine immunohistochemical marker. Nineteen of 19 (100%) of neuroendocrine carcinomas expressed at least one neuroendocrine marker. 

Large cell undifferentiated neuroendocrine carcinoma (LCNEC) can present as CUPS, and it is easy to miss the diagnosis without applying the appropriate neuroendocrine markers. The correct diagnosis of LCNEC is an important distinction because it carries the same dismal prognosis as does small cell carcinoma, whether in the lung or gastrointestinal tract. 776 Synaptophysin may be the most frequent positive marker in LCNEC. ... 

The immunophenotype of large cell undifferentiated neoplasms of lung is unpredictable. Most large cell undifferentiated neoplasms are carcinomas and coexpress keratin and vimentin. Some express only vimentin. There are large cell neoplasms that look like carcinomas but, in fact, are not. Another area of potential confusion is related to observations that non-neuroendocrine, non-small cell carcinomas as determined by histologic appearances express neuroendocrine markers by immunohistochemistry. We will discuss this concept later in this chapter. 

Wick MR, Berg LC, Hertz ML Large cell carcinoma of the lung with neuroendocrine differentiation A comparison with large cell undifferentiated pulmonary tumors. Am J Clin Pathol. 1992 97 796-805. 

Almost all squamous cell carcinomas, half of transitional cell carcinomas, and many undifferentiated large cell carcinomas immunostain with CK5/6 (Table CK5/6 has excellent sensitivity and specificity for the detection of squamous differentiation in poorly differentiated carcinomas.p63 is also seen with high frequency in squamous and transitional carcinomas, and when used with the CK5/6 antibody affords high sensitivity and specificity for squamous differentiation. 758... 

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