Anatomic pathology selected abstracts

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Pathological features associated with metastasis in early invasive colorectal carcinoma in colorectal polyps

Complete endoscopic resection alone can, in many cases, sufficiently treat colorectal carcinoma arising in a colorectal polyp with invasion limited to the submucosa. Histological features of colorectal carcinoma, including tumor size, vascular invasion, and poor tumor differentiation or evidence of de-differentiation, such as tumor budding, are associated with a higher risk for metastasis, thereby supporting the recommendation for oncological resection. However, most malignant polyps with these features do not have lymph node metastases at the time of resection, necessitating better refinement of the histological risk features. The authors investigated the predictive value of known and potentially novel pathological factors in a cohort of pT1 colorectal carcinomas enriched for those with lymph node metastases and those that underwent endoscopic polypectomy. In the 466-person study group, there were 437 consecutive colorectal polyps with submucosal invasive carcinoma from a single center, 57 of which had metastatic disease, supplemented by 30 cases of known metastatic disease from two additional centers. Clinical and histological features of the polyp cancers were reviewed to determine the differences between 87 cancers that were metastatic and the remaining cases without metastasis. A subgroup of 204 polyps removed intact was also analyzed to ensure maximum histological accuracy. This study confirmed larger invasive tumor size, vascular invasion, and poor tumor differentiation as adverse predictive features. Other prominent adverse features included peritumoral desmoplasia and high cytological grade. A predictive logistic-regression model utilizing the presence of any form of vascular invasion, presence of high tumor budding (BD3), width of invasive tumor component greater than 8 mm, depth of invasive tumor greater than 1.5 mm, and findings of prominent expansile desmoplasia within and beyond the deep invasive edge of the carcinoma showed excellent performance in predicting metastatic disease.

Brown I, Zammit AP, Bettington M. Pathological features associated with metastasis in patients with early invasive (pT1) colorectal carcinoma in colorectal polyps. Histopathology. 2023;83(4):591–606.

Correspondence: Dr. Ian Brown at ianbrown@envoi.com.au

Use of Texas Red-filtered microscopy to increase specificity of Congo red stain for amyloid

The diagnosis of amyloidosis via tissue biopsy is traditionally suggested by H&E stain and confirmed by Congo red stain, both of which are used in routine light microscopy. False-positive and false-negative congophilia are well documented, limiting the sensitivity and specificity of Congo red stain for diagnosing amyloidosis. Using Texas Red-filtered fluorescence microscopy (TRFM) to examine Congo red-stained tissue is known to enhance amyloid-specific congophilia, thereby increasing diagnostic sensitivity. The authors conducted a study to determine whether TRFM can mitigate the false positivity seen with light microscopy and thus improve the specificity of Congo red stain in detecting amyloid deposits in histology sections from a variety of tissue types. Ninety-two tissue samples were selected for the study and categorized into three groups. Group one included 15 samples with tissue deposition of amyloid. Group two consisted of 63 samples in which amorphous eosinophilic structures reminiscent of amyloid were seen on H&E-stained tissue sections. Group three included 14 samples in which amyloid and amyloid-like tissue were seen side by side. Clinicopathologic correlation was used to rule in or rule out amyloidosis in each case. The congophilic areas in each case were identified by light microscopy and then examined by TRFM. TRFM confirmed the diagnosis of amyloidosis in all group one cases by enhancing the congophilic areas. Enhancement was not seen in 52 of the 63 group two cases. TRFM enhanced amyloid-specific congophilia, but not nonspecific congophilia, in all group three cases. The authors concluded that TRFM increases the diagnostic yield and specificity of Congo red-stained tissue sections for detecting amyloid.

Shehabeldin A, Hussey C, Aggad R, et al. Increased diagnostic specificity of Congo red stain for amyloid: The potential role of Texas Red–filtered fluorescence microscopy. Arch Pathol Lab Med. 2023;147(8):907–915.

Correspondence: Dr. Ahmed Shehabeldin at a.shehabeldin@gmail.com