Increased expression of α-methylacyl-coenzyme A racemase (AMACR; p504s) and p16 in distal hyperplastic polyps

Distinctive crypt shape in a sessile serrated adenoma/polyp: Distribution of Ki67-, p16INK4a-, WNT5A-positive cells and intraepithelial lymphocytes

Serrated lesions in the colorectum are currently predominantly classified as hyperplastic polyps (HPs), sessile serrated adenomas/polyps (SSA/Ps), and traditional serrated adenomas (TSAs) according to their morphology. However, the histological morphology and the molecular changes in the serrated lesions are still unclear. We performed immunohistochemistry for Ki67, p16^INK4a, and WNT5A in human HPs (n=22), SSA/Ps (n=41), and TSAs (n=19). The distribution of Ki67 and p16^INK4a positive cells in TSAs was different from that in HPs and SSA/Ps. Co-expression of Ki67 and P16^INK4a was infrequent in HPs and SSA/Ps; p16^INK4a-positive cells were found in the crypt cleft and stromal WNT5A-positive stromal cells were localized near the cleft in SSA/Ps, while intraepithelial lymphocytes (IELs) in SSA/Ps were more abundant than HPs. In conclusion, our study provides evidence that HPs branch because of the increase in and patchy distribution of senescent and proliferative cells, with increased and misdistributed stromal and inflammatory cells, which might contribute to creation of L- and/or T-shaped crypts, which are of distinctive shapes in SSA/Ps. Our findings may facilitate better understanding and therapy in the serrated lesions.

α-Methylacyl-coenzyme A racemase (AMACR, p504s) is a marker to distinguish malignant melanomas from dysplastic nevi and melanocytic nevi

Routinely processed skin biopsies are still the mainstay for the diagnosis of melanocytic skin neoplasms (MSNs) and are considered the "gold standard" for individual patient management and clinical trials. The diagnostic challenge of melanocytic lesions of the skin prompts histopathologists to consider new diagnostic tools; among these, immunohistochemistry. We aimed to find putative new immunohistochemical markers, which can supplement the histological criteria used to detect dysplasia. In this immunohistochemical study, we chose a panel of promising biomarkers which could potentially differentiate between different MSN entities. These included α-methylacyl-coenzyme A racemase (AMACR; p504s), which is involved in the degradation of branched chained fatty acid derivates. We analysed a cohort of benign nevi and malignant melanomas. The design of the study included 78 melanocytic skin neoplasms (26 malignant melanomas and 52 benign nevi) in a tissue microarray. Immunohistochemistry of cyclin-dependent kinase inhibitor 2A (p16Ink4a), methylacyl-coenzyme A racemase (AMACR), cyclin D1, and E-cadherin was performed and assessed. We have observed that the p16Ink4a, AMACR, cyclin D1, and E-cadherin showed no exclusive staining for nevi or melanomas. However, a significant overexpression of AMACR was found in malignant melanomas compared to benign nevi. AMACR overexpression was also associated with an increased p16Ink4a staining. Our results suggest AMACR as an immunohistochemical marker for distinguishing malignant melanomas and dysplastic nevi from conventional melanocytic nevi.

Recurrent adult jejuno-jejunal intussusception due to inflammatory fibroid polyp - Vanek's tumour: a case report

Background

Adult intussusception is a rare but challenging condition. Preoperative diagnosis is frequently missed or delayed because of nonspecific or sub-acute symptoms.

Case presentation

We present the case of a sixty-two year old gentleman who initially presented with pseudo-obstruction. Computerised tomography displayed a jejuno-jejunal intussusception, which was treated by primary laparoscopic reduction. The patient re-presented with acute small bowel obstruction two weeks later. He underwent a laparotomy showing recurrent intussusception and required a small bowel resection with primary anastomosis. Histological examination of the specimen revealed that the intussusception lead point was due to an inflammatory fibroid polyp (Vanek’s tumour) causing double invagination.

Conclusions

Adult intussusception presents with a variety of acute, intermittent, and chronic symptoms, thus making its preoperative diagnosis difficult. Although computed tomography is useful in confirming an anatomical abnormality, final diagnosis requires histopathological analysis. Vanek’s tumours arising within the small bowel rarely present with obstruction or intussusception. The optimal surgical management of adult small bowel intussusception varies between reduction and resection. Reduction can be attempted in small bowel intussusceptions provided that the segment involved is viable and malignancy is not suspected.

Virtual Slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/7292185123639943