Gut-associated lymphoid tissue or so-called “dome” carcinoma of the colon: Review

Emerging and under-recognised patterns of colorectal carcinoma morphologies: a comprehensive review

While the overwhelming majority of colorectal carcinomas (CRC) are diagnosed as adenocarcinoma not otherwise specified, there are numerous under-recognised morphologic patterns of CRC. These patterns are recognised by the WHO, appear in reporting manuals for the American Joint Committee of Cancer, and/or are listed on synoptic reports, while many other variants have either fallen out of favour or are emerging as future bona fide patterns. Herein, we discuss 13 variants: serrated adenocarcinoma, micropapillary adenocarcinoma, medullary carcinoma, neuroendocrine carcinoma, mucinous adenocarcinoma, signet-ring cell carcinoma, adenosquamous carcinoma, adenoma-like adenocarcinoma, lymphoglandular complex-like CRC, carcinoma with sarcomatoid components, cribriform-comedo-type adenocarcinoma, undifferentiated carcinoma and low-grade tubuloglandular adenocarcinoma. The purpose of this review is to scrutinise these variants by assessing their clinical characteristics, morphologic cues, as well as pitfalls, and address their prognostic significance. Our analysis aims to bring clarity and updated understanding to these variants, offering valuable insights for pathologists. This contributes to more nuanced CRC diagnosis and treatment strategies, highlighting the importance of recognising a broad spectrum of morphologic patterns in CRC.

Lymphoglandular Complex-Like Colorectal Carcinoma-A Series of 20 Colorectal Cases, Including Newly Reported Features of Malignant Behavior

Distinguishing colon carcinoma that is surrounded by well-circumscribed lymphoid tissue from adenomas involving lymphoglandular complexes can be difficult. We assessed a multi-institutional international cohort of 20 colorectal carcinomas with associated prominent lymphoid infiltrates, which we referred to as lymphoglandular complex-like carcinoma (LGCC). We collected clinical and endoscopic features, including lesion size, endoscopic appearance, location, procedure, follow-up, AJCC stage, and mismatch repair status. We recorded the presence of the following histologic features: haphazard gland distribution, gland angulation, gland fusion, solid nest formation, single-cell formation, stromal desmoplasia, presence of lymphovascular invasion and perineural invasion, presence of lamina propria, cytologic atypia as low- or high-grade, presence of goblet cells in the invasive component, and the presence of a surface lesion. Most cases (9 of 13) were described endoscopically as sessile polyps with an average size of 1.56 cm. Most cases (90%) were associated with a surface lesion, of which the majority were tubular adenomas, though a subset was associated with sessile serrated lesions with dysplasia (3 of 18). All cases of LGCC demonstrated haphazard gland distribution and either gland angulation, fusion, or solid nest formation. A portion of cases demonstrated single-cell infiltration (35%) and desmoplasia (50%), and rarely lymphovascular invasion was present (5%). A subset (10%) of cases invaded beyond the submucosa. Deficient mismatch repair was present in 22% (2 of 9) of cases for which it was performed. In cases of colectomy or completion colectomy, nodal metastasis was present in 38% (3 of 8). No cases demonstrated disease recurrence or disease-specific mortality. Overall, LGCC represents an enigmatic subset of carcinomas that is important to distinguish from adenomas involving lymphoglandular complexes due to its varying prognostic outcomes.

Gut-associated Lymphoid Tissue/Dome-Type Carcinoma of the Colon: A Rare Case Report With Review of the Literature

Gut-associated lymphoid tissue (GALT) carcinoma, also termed dome-type carcinoma, is an infrequent distinctive subtype of colorectal adenocarcinoma and only 18 cases have been reported in the English medical literature. These tumors have unique clinicopathological features and are considered to have a low malignant potential with favorable prognosis. Herein, we described a case of a 49-year-old male with intermittent hematochezia for 2 years. Colonoscopy revealed a sessile broad-based polyp of approximately 20 mm × 17 mm in the sigmoid colon 260 mm away from the anus, with a slightly hyperemic surface. Histologically, this lesion showed typical GALT carcinoma. The patient was followed up for one and a half year and he did not experience any discomfort, such as abdominal pain or hematochezia, and no tumor recurrence occurred. Moreover, we reviewed the literature, summarized the clinicopathological features of GALT carcinoma, and highlighted its pathological differential diagnosis to further explore this infrequent type of colorectal adenocarcinoma.

Molecular profiling of the intestinal mucosa and immune cells of the colon by multi-parametric histological techniques

The impact of the post-mortem interval (PMI) on the optical molecular characteristics of the colonic mucosa and the gut-associated lymphoid tissue (GALT) were examined by multi-parametric measurements techniques. Inflammatory cells were identified by immunohistochemical staining. Molecular parameters were estimated using the Raman spectroscopy (RS) and Fourier Transform Infrared (FTIR) spectroscopic imaging. The 3D refractive index (3D-RI) distributions of samples were determined using the digital holographic tomography. The distribution of immune cells between post-mortem (PM) and normal controls did show significant differences for CD4 (P = 0.0016) or CD8 (P < 0.0001), whose expression level was decreased in PM cases. No association was found between individual PMI values and inflammatory cell distribution. However, there was a tendency for a negative correlation between CD4⁺ cells and PMI (r = - 0.542, P = 0.032). The alterations ongoing in post-mortem tissue may suggest that PMI has a suppressive effect on the effector properties of the cell-mediated immunity. Moreover, it was confirmed that spectroscopic and digital holotomographic histology are also a useful technique for characterization of the differences in inflammation of varying intensity and in GALT imaging in a solid tissue. Anatomical location of immune cells and methods of tissue fixation determine the molecular and optical parameters of the examined cases.

A Focused Review on Advances in Risk Stratification of Malignant Polyps

Colorectal cancer is the third most common cancer in both men and women in the United States, with most cases arising from precursor adenomatous polyps. Colorectal malignant polyps are defined as cancerous polyps that consist of tumor cells invading through the muscularis mucosae into the underlying submucosa (pT1 tumor). It has been reported that approximately 0.5-8.3% of colorectal polyps are malignant polyps, and the potential for lymph node metastasis in these polyps ranges from 8.5% to 16.1%. Due to their clinical significance, recognition of malignant polyps is critical for clinical teams to make treatment decisions and establish appropriate surveillance schedules after local excision of the polyps. There is a rapidly developing interest in malignant polyps within the literature as a result of an increasing number of identifiable adverse histologic features and recent advancements in endoscopic treatment techniques. The purpose of this paper is to have a focused review of the recent histopathologic literature of malignant polyps.

Colorectal epithelial neoplasm associated with gut-associated lymphoid tissue

BACKGROUND

Colorectal epithelial neoplasm extending into the submucosal gut-associated lymphoid tissue (GALT) can cause difficulties in the differential diagnosis. Regarding GALT-associated epithelial neoplasms, a few studies favor the term "GALT carcinoma" while other studies have mentioned the term "GALT-associated pseudoinvasion/epithelial misplacement (PEM)".

METHODS

The clinicopathologic characteristics of 11 cases of colorectal epithelial neoplasm associated with submucosal GALT diagnosed via endoscopic submucosal dissection were studied.

RESULTS

Eight cases (72.7%) were in males. The median age was 59 years, and age ranged from 53 to 73. All cases had a submucosal tumor component more compatible with GALT-associated PEM. Eight cases (72.7%) were located in the right colon. Ten cases (90.9%) had a non-protruding endoscopic appearance. Nine cases (81.8%) showed continuity between the submucosal and surface adenomatous components. Nine cases showed (81.8%) focal defects or discontinuation of the muscularis mucosae adjacent to the submucosal GALT. No case showed hemosiderin deposits in the submucosa or desmoplastic reaction. No case showed single tumor cells or small clusters of tumor cells in the submucosal GALT. Seven cases (63.6%) showed goblet cells in the submucosa. No cases showed oncocytic columnar cells lining submucosal glands.

CONCLUSIONS

Our experience suggests that pathologists should be aware of the differential diagnosis of GALT-associated submucosal extension by colorectal adenomatous neoplasm. Further studies are needed to validate classification of GALT-associated epithelial neoplasms.

A case of a rectal adenocarcinoma mimicking a neuroendocrine tumor in the background mucosa of amoebic colitis

A 54-year-old man with diarrhea and hematochezia for 2 months was referred to our department. A total colonoscopy revealed amoebic colitis caused by Entamoeba histolytica. Concurrently, a submucosal tumor-like yellowish hemispheric polypoid lesion was incidentally detected in the rectum. We speculated that the lesion was a NET, which could be cured by endoscopic treatment. However, histopathological assessment of a biopsy specimen unexpectedly revealed a well- or moderately differentiated adenocarcinoma. After treatment of the amoebic colitis, endoscopic ultrasound revealed a low, hetero-echoic, 6-mm-diameter lesion mainly in the submucosal layer. We performed surgical resection because the invasion was estimated to be to the deeper submucosal layer. Histopathological assessment of the surgically resected specimen revealed a focal lesion of a well-differentiated adenocarcinoma in the granulation tissue of the submucosal layer. In cases accompanied by amoebic colitis, a tumor's initial gross type might change. Diagnostic endoscopic resection could be acceptable in such cases.