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Pulmonary enteric adenocarcinoma (PEAC), a extremely rare variant of primary invasive adenocarcinoma of the lung, was recognized by the international multidisciplinary classification of lung adenocarcinoma which was proposed by the International Association for the Study of Lung Cancer (IASLC), the American Thoracic Society (ATS), and the European Respiratory Society (ERS) published in early 2011. Histologically, PEAC is considered to be mainly composed of tall columnar cells arranged in an irregular glandular cavity or cribriform pattern with extensive central necrosis which show high resemblance to that of intestinal epithelia and colorectal carcinomas. Immunohistochemically, PEAC can not only expresses typical proteins common to lung primaries but is positive for at least one intestinal markers, such as CDX2, cytokeratin (CK) 20, MUC2, therefore, the differentiation of primary PEACs from metastatic colorectal cancers can be challenging. In this study, we report 9 cases of PEAC and a panel of immunohistochemical protein markers of CK7, CK20, thyroid transcription factor 1 (TTF-1), Napsin A, MUC2 and villin was analyzed with the comparison of 20 metastatic colorectal carcinomas (MCRs), and 20 typical primary adenocarcinomas (tPACs). As was expected, CK7 expression was documented in all 9 PEACs and 20 tPCAs while CK20 was significantly more prevalent in adenocarcinoma that originated from colorectal. Additionally, we evaluate the classical mutations of EGFR, KRAS in the 9 cases of PEACs, it turned out that all tumors were EGFR-wild and KRAS-wild types, which confirmed that PEAC has a separate phenotype from usual pulmonary adenocarcinoma.

Papillary renal cell carcinoma (PRCC) is traditionally classified into type 1 and type 2. Recently, an oncocytic variant of PRCC has been described. We report a series of 6 oncocytic renal papillary tumors (OPRCC) which tended to occur in older patients (mean, 56.8 years) with a male preference (male-to-female ratio is 5:1). All 6 patients are alive with no evidence of disease after initial resection, showing an indolent clinical behavior. Histologically, tumors exhibited predominant papillary structure with delicate fibrovascular cores. Papillae were lined by single layers of cells with large, deeply eosinophilic and finely granular cytoplasms and round regular nucleus. The phagocytosis of tumor cells was frequently and evidently seen in our cases that hemosiderin-laden tumor cells and foamy tumor cells were noticed in five and four cases respectively. All tumors were immunoreactive for racemase, vimentin, CD10, and MET and negative for CD117. While E-cadherin, EMA, and cytokeratin 7 exhibited variable immunopositivity. FISH analysis was performed in five of six cases and found heterogeneous results. Trisomy of chromosomes 7 was found in three cases and trisomy of chromosomes 17 in two cases. Loss of chromosome Y was noted in one of four tumors in male patients. MET gene status was also investigated by direct sequencing in all 6 cases and found no distinct mutation in any case. These results suggest that OPRCC shows distinct morphology, indolent clinical behavior, and similar immunohistochemical and cytogenetic features with PRCC, seems to be a variant in the PRCC group. Whether the strong expression of MET indicates a potential therapeutic target is still unknown and requires further investigation in clinical trials.