Triple marker composed of p16, CD56, and TTF1 shows higher sensitivity than INSM1 for diagnosis of pulmonary small cell carcinoma: proposal for a rational immunohistochemical algorithm for diagnosis of small cell carcinoma in small biopsy and cytology specimens.

Pulmonary small cell carcinoma (SCLC) can be usually diagnosed based on the morphological evaluation of routine histological or cytological preparations. However, immunohistochemistry may be also necessary in problematic cases. Insulinoma-associated 1 (INSM1) has recently been reported as a highly sensitive and specific marker that displays positivity in ~90%-100% of poorly differentiated pulmonary neuroendocrine tumors. We compared diagnostic performance of INSM1 and previously reported composite marker CD56 + p16 + thyroid transcription factor-1 (TTF1) in the diagnosis of SCLC in small biopsy specimens and cytoblocks. The composite marker CD56 + p16 + TTF1 correctly classified 100% of SCLC cases, and its sensitivity was significantly higher than the sensitivity of INSM1. Among 100 SCLC cases, CD56, TTF1, and p16 each individually classified more specimens correctly than INSM1 (CD56: 84%, TTF1: 89%, p16: 95%, INSM1: 81%); the difference was statistically significant only for p16. INSM1 showed the lowest classification agreement between paired biopsy and cytoblock specimens (κ = 0.182), whereas CD56 and p16 displayed perfect agreement (κ = 1) and TTF1 showed moderate agreement (κ = 0.4). Although INSM1 is reportedly the most specific marker of SCLC, its sensitivity is not superior to p16 or composite marker CD56 + TTF1 + p16. Based on this study, we propose the following algorithm, which, in the appropriate clinical and histological context, may be useful in establishing the correct diagnosis of SCLC: First, INSM1 detection is performed, and if the result is negative, CD56 is added, followed successively by p16 and TTF1 if all previously applied markers are negative. This approach should detect most, if not all, SCLC cases, while successively trading specificity for sensitivity.

Frozen section examination of pancreas, gallbladder, extrahepatic biliary tree, liver, and gastrointestinal tract.

The main indications for intraoperative consultation of gastrointestinal tract, liver, and pancreatobiliary system are to evaluate the resection margin and to make a tissue diagnosis of lesions for which preoperative histology is not aviable for various reasons. Special situations include the evaluation of liver donor biopsies for the presence of steatosis and inflamation, or determination that ganglion cells are present in the bowel wall at the level where the anastomosis will be placed in case of Hirschprung's disease. The most worrisome pitfalls include differentiating pancreatic ductal carcinoma from chronic pancreatitis, distinguishing biliary tree and gallbladder carcinoma from reactive changes caused by inflammation, and recognizing the presence of diffuse adenocarcinoma at the resection margin of the esophagus and stomach. Keywords: frozen section - gastrointestinal tract - liver - gallbladder - extrahepatic biliary tree - pancreas.

Results of morphological screening for Lynch syndrome during the period 2013-2016.

The introduction of a screening system for Lynch syndrome in pathology laboratories in Plzen yielded 24 diagnoses of Lynch syndrome during the period of 2013-2016, 20 of them presenting with colorectal cancer. In 8 of those 24 cases germline mutations of MMR genes, previously not recognized as pathogenic with certainty, were detected. Although the frequency of Lynch syndrome in patients with colorectal cancer was only 0.34 % in total, following introduction of the universal immunohistochemical investigation of MMR (mismatch repair) proteins expression in all colorectal cancers examined in Sikl´s Institute of Pathology the frequency per year in this department reached 2.4 %. The results favor universal immunohistochemical screening for Lynch syndrome in colorectal and endometrial cancer cases over a selective approach based on a combination of clinical and morphological criteria. Increased effectiveness of the universal approach is not brought about only by higher sensitivity of the immunohistochemical examination per se, but also by the possibility of automation of the process leading to increased adherence even of pathologists not directly engaged in Lynch syndrome management. However, the introduction of a nation-wide universal screening system requires support from the government and health insurance companies. Keywords: colorectal cancer - endometrial cancer - immunohistochemistry - Lynch syndrome - MMR - screening.

P16 is a useful supplemental diagnostic marker of pulmonary small cell carcinoma in small biopsies and cytology specimens.

Pulmonary small cell carcinoma (SCLC) is usually diagnosed in small biopsy or cytological specimens based on cytomorphology; however in ambiguous cases diagnosis requires additional support by immunohistochemistry. While TP53 and RB1 alterations with secondary overexpression of p16 are mainstay events in SCLC pathogenesis, diagnostic value of p16-positivity in the diagnosis of SCLC has not yet been fully investigated. We examined the expression of p16, CD56, synaptophysin (SYP), chromogranin A and thyroid transcription factor-1 (TTF1) in a series of pulmonary and extrapulmonary small cell carcinomas, pulmonary carcinoids and non-small cell lung carcinomas, and compared diagnostic performance of these markers in the diagnosis of SCLC. P16 was positive in 95 of 101 SCLCs, and displayed highest diagnostic sensitivity of ~94%. Composite biomarkers CD56+p16+TTF1 and CD56+p16+SYP were both able to detect correctly all SCLC cases. Importantly, three (~3%) SCLC cases completely negative for all conventional markers displayed diffuse positivity for p16. CD56 and p16 demonstrated highest concordance between paired small biopsy and cytology specimens. 50% of squamous cell carcinomas, ~41% of adenocarcinoma/NSCLC-favour adenocarcinoma cases, and ~93% of extrapulmonary small cell carcinomas also showed p16-positivity. Combination of CD56, p16 and TTF1 produced diagnostic classifier that outperformed best single marker CD56 in differential diagnosis between SCLC and NSCLC. In conclusion, in the appropriate morphological context p16 represents a useful supplementary marker for diagnosis of SCLC, even in cases where only cytological material is available.

Nonsyndromic Intestinal Lipomas are Probably not Associated With Mutations of PDGFRA.

The purpose of this study was to test the hypothesis that intestinal lipomas occurring in patients devoid of signs of PDGFRA-mutant syndrome might represent sporadic counterparts of familial lipomatous tumors occurring in the spectrum of tumors associated with PDGFRA mutations. PDGFRA-mutant syndrome may manifest with gastrointestinal stromal tumors, Vanek tumors, fibrous tumors, and lipomatous tumors. Until now there has been no molecular genetic study of PDGFRA mutations in intestinal lipomas published in the world literature. A series of 20 intestinal lipomas were obtained from 17 patients, and mutational analysis of exons 12, 14, and 18 of the PDGFRA gene was performed. None of the 16 analyzable tumors showed mutations in PDGFRA. Thus, PDGFRA mutations probably do not play an important role in the development of sporadic lipomas of the intestines.