The Daily Sign-Out

New proposal for histological grading in colorectal carcinoma

I find it surprising that histological grading for two of the most common adult malignancies--colon and lung--lacks any kind of consensus criteria for grading elements let alone clinical validation as a prognostic marker.  I have previously blogged on proposals for grading for lung adenocarcinoma but the February 2012 issue of American Journal of Surgical Pathology has an intriguing proposal for criteria for grading of colorectal cancer by Hideki Ueno et al. (abstract).

I am most familiar with Dr. Ueno's previous work on tumor budding in colon cancer (you should be too!) and this work builds on and expands on this work.  In contrast to tumor budding, defined as invasive single cells and/or clusters with <5 cells, this work describes and defines the significance of "poorly differentiated clusters" for grading.  Poorly differentiated clusters are defined by these authors as "cancer clusters in the stroma composed of >5 cancer cells and lacking a gland-like structure."  These clusters are identified at low power and then counted per 20X (1-mm diameter) field.  The color illustrations included in the text are particularly well-selected and beautifully reproduced.  Grading was also assessed independently by assessing quantitatively the area of the tumor involved by poorly differentiated clusters and by tumor budding.

Although this is a single institution study, it included 500 consecutive patients with stage 2 or stage 3 CRC who underwent curative resection and had follow-up on 97% (!) of these patients (483 patients) for a median of 68 months for the 378 surviving patients.

Three things stand out from the results.  First, there was excellent separation in 5-Year DFS using quantity of poorly differentiated clusters as the criterion for grading: grade 1--96%, grade 2--85%, grade 3--59%.  Second, tumor grading based on poorly differentiated clusters, T and N stages, and venous invasion were independent prognostic parameters related to survival on mutlivariate analysis.  FInally, the authors measured intra- and inter-observer variability in tumorg grading based on poorly differentiated clusters.

This is an interesting and status quo-challenging article that should provoke some good discussion amongst GI specialist and general pathologists.

Digital Case: Simple mucocele of the appendix

Finally, I'm working on sharing some interesting cases that have come across my desk recently! We've seen some interesting appendix pathology of late, including this case.

Here's a couple views of the microscopic features.  The cyst mostly showed an atrophic lining which in most areas was lacking entirely--

--but focally had a benign reactive colonic-type epithelial lining associated with lamina propria acute and chronic inflammation.

Adenomas and other epithelial neoplasms that produce a "mucocele" (=cystic distension by mucous) must be ruled out.  I suppose the main differential diagnoses include appendiceal cystadenoma and low-grade appendiceal mucinous neoplasm, followed by adenomas associated with appendiceal dilation and low-grade mucinous adenocarcinoma.  Appendiceal mucoceles are usually considered to be a post-inflammatory sequela and not neoplastic.  Synonyms include retention cyst and inflammatory mucocele.  Obviously, the entities in the d/dx are indeed neoplastic.  In low-grade appendiceal mucinous neoplasm, the appendix is usually enlarged and fusiform, weirdly deformed or completely destroyed.  Microscopically, the lining typically shows short villiform tufts but the epithelium may be lost or flat in areas.  One may also see the epithelium invaginating deeply into the wall of the lesion without definitive invasion.  The appendix may be dilated or even normal with adenomas.  Most seem to me to be villous, although the literature has recently identified serrated adenomas to also be common. When an adenoma is associated with dilatation, the term cystadenoma is frequently used.  Definitely one needs to extensively sample the specimen when a cystic abnormality is identified grossly or when the above microscopic features are seen. 

Examination of colon specimens resected for polyposis

One of my colleagues received a 40-cm left colectomy specimen from a 49-year-old woman that I diagnosed with a grade 1 T3N0 cecal adenocarcinoma in August of 2011.  MMR testing by IHC at that time showed proficient (or intact) MMR proteins.  The specimen contained around 20 or so separate and discrete polyps with a range of sizes (0.4 to 1.5 cm) and configurations (pedunculated to sessile)--but none which appeared grossly canacerous.

We consulted our trusted tomes and PubMed but were unable to find any published protocols for what constitutes even "adequate" sampling for colectomy specimens resected for polyposis.  Is anyone out there aware of such a protocol?

My colleague (wisely) decided to sample all the sessile and/or >1 cm polyps.  As it turned out, a T1 adenocarcinoma was identified in one such polyp and a Tis lesion in another.  Lymph nodes were negative but, I would add, the surgery was performed laparoscopically and the mesenteric cuff was (ahem) abbreviated.

Any thoughts?

Recent article collection on colorectal cancer

Nature Reviews Clinical Oncology and Nature Reviews Gastroenterology and Hepatology have put together a superb collection of state-of-the-art reviews on various aspects of colorectal cancer that is currently free to access and download.

This collection of articles published in the past 18 months from these journals comprises a selection of 9 Reviews, 3 Perspectives, 17 News & Views, and 12 Research Highlights that discuss advances in the understanding of the screening, diagnosis, prevention and treatment of this disease, as well as highlighting the challenges and future directions in this field.

There is a tonne of great content here that, if anything else, gives you a one-stop shopping reference and the material is timely and relevant.

Nice reading for a lovely fall weekend!  Don't forget to set your clocks back Saturday night.

Digital Case Challenge: Enterobius vermicularis (Pinworm)

The day before the (U.S.) Thanksgiving, I saw this case.  It was identified as simply "colon biopsy" but the pathology assistant noted white thready "mucosal" fragments measuring about 4 mm to 5 mm in length.

The ova are usually described as being about 30 X 50 microns but I think these are slightly smaller due to formalin fixation and routine processing, while this diagnosis is usually made by the "Scotch tape" technique pressed onto perianal skin.  Uncommon as a colonoscopic specimen.  This parasite is transmitted by a fecal-oral route and does not require an intermediate host.  Didn't obviously want to post this around the holiday.

Genomics and Inflammatory Bowel Disease

I think it fair to state that elucidating the pathogenesis of inflammatory bowel disease (IBD--ulcerative colitis and Crohn's disease) has been a decades-long exercise in futility. But recently published and presented genome-wide association studies (GWAS) in (IBD) have advanced the understanding of the pathogenesis of IBD.  The International IBD Genetics Consortium presented 2 key studies at the recent Digestive Diseases Week 2010 conference.

One of these studies was presented in the "Immunology, Microbiology, and Inflammatory Bowel Disease Distinguished Abstract Plenary" session by the Consortium authored by Parkes et al (abstract) was an multinational GWAS of CD in patients of European descent that identified 18 new susceptibility loci associated with CD that includes candidate genes such as NOTCH1, SMAD3, ICAM3/ICAM5, and MUC1.

A similarly designed study of UC involving N.American and European patients was presented in the "Clinical Practice Distinguished Abstract Plenary" session by John Rioux of the IBD Genetics Consortium (abstract).  This study identified 75 independent susceptibility loci associated with UC, including all previously identified susceptibility loci and 20 new loci that appear to be UC-specfic.  Interestingly, about half of the 75 loci have previously been associated with CD and of the ~45 putative novel loci, 25 have previously been associated with other autoimmune chronic inflammatory diseases.  These results strongly support the hypothesis that certain biological pathways are common between inflammatory diseases.  Although the Consortium currently testing all novel loci in an independent group of UC patients, preliminary results provide convincing evidence of association to genes with likely biological significance to disease pathogenesis, including TNFRSF14, JAK2, and CARD9.

This is some very interesting data that not only demonstrate the power of GWAS but also are first steps in identifying markers for IBD and molecular pathways in the pathogenesis of IBD that could be exploited in developing pharmacological targets.

Members of the Consortium recently published a review of UC susceptibility loci in Nature Genetics 2010;42:332-337.

Prognostic factors in T1 colorectal adenocarcinoma

A frequently encountered specimen is the adenocarcinoma with submucosal invasion arising in a dysplastic adenomatous polyp or sessile lesion that has been resected endoscopically.  While much effort is directed at determining margin adequacy and depth of invasion, less attention has been given to other parameters that may be associated with risk of lymph node (LN) metastasis. Measuring the depth of invasion is frequnetly problematic given the morcellated nature of most specimens.  Generally, if the lesion is felt to be adequately excised, a formal colectomy may not necessarily be needed since the risk of LN metastasis in a T1 tumor is felt to be too low to warrent the morbidity of a colectomy.

A recent article in the August 2010 Modern Pathology sought to detect patients at high risk for LN metastasis after endoscopic mucosal resection.

Tateishi Y, Nakamishi Y, Taniguchi H et al.  Pathological prognostic factor spredicting lymph node metastasis in submucosal invasive (T1)colorectal adenocarcinoma.  Mod Pathol 2010;23:1068-1072.

This is a single-institution study that examined 322 consecutive patients treated by colectomy (complete tumor excision plus lymphadenectomy) for T1 colorectal adenocarcinoma.  The entire lesion was examined microscopically in all cases and criteria evaluated for the study included submucosal invasive depth, tumor size, lymphatic invasion, venous invasion, histologic grade, tumor budding at the submucosal invasion front, and status of muscularis mucosae.

The authors found LN metastases in 14.3% of patients (46/322)--which was a surprising and sobering finding in itself to me.  By univariate analysis, tumor budding, histologic grade, lymphatic invasion, venous invasion, submucosal invasion depth > 1 mm, and completely disrupted (type B) muscularis mucosae were associated with LN metastasis.  By multivariate analysis, however, only tumor budding, high grade tumor differentiation, and lymphatic invasion were associated with LN metastasis.  Moreover, of the 46 patients with LN metastasis, 40 (87%) had at least 1 out of 3 factors by multivariate analysis associated with LN metastasis; the remaining 6 all showed type B muscularis mucosae status.  Using these four criteria, 285 out of 322 patients were positive for at least one criteria and would have undergone colectomy after submucosal resection--for 100% sensitivity but only 13.4% specificity.

Certainly, the decision whether colectomy is the most appropriate definitive treatment following endoscopic resection must be individualized.  But it seems in my experience that this is a gray zone for surgeons and oncologists and these criteria, while needing independent and prospective validation, are worthy of further study and consideration of being adopted for routine use now.  The evaluation of muscularis mucosae status is not familiar in the U.S. and the reader is referred to the original article by Tominga et al in Dis Colon Rectum (2005) for more detail.

The practical points here are 1) that these parameters can be readily assessed in routine H&E sections and 2) using four histologic risk factors--tumor budding, lymphatic invasion, high-grade histologic tumor differentiation (moderately- to poorly-differentiated), and type B muscularis mucosae status--the authors were able to select all patients who were shown to have LN metastasis. 

Leave well enough alone? The role of resection in asymptomatic metastatic CRC

The standard of care for treatment of mCRC has been surgical resection followed by adjuvant chemotherapy.  In patients presenting with symptomatic mCRC, palliative surgery is performed for bleeding, obstruction, or perforation, while in patients presenting with non-emergent symptoms and limited disease, surgery may be undertaken with a curative intent.  The role and value of surgery in patients with unresectable stage 4 colon cancer and a synchronous asymptomatic primary tumor is being currently investigated by the National Surgical Adjuvant Breast and Bowel Project in a prospective phase II study (NSABP C-10).  Current recommendations for treatment of mCRC are:

1. Patients with evidence of significant obstruction, perforation, or uncontrolled bleeding should undergo resection of the symptomatic lesion.
2. Patients who are unfit for surgery, or who decline surgery, should undergo endoscopic management with stents or ablation to palliate symptoms.
3. Patients with potentially resectable metastases should undergo resections of both the primary tumor and the metastases (typically, sequentially).
   1. Chemotherapy may be administered preoperatively to assess the natural history of the underlying malignancy.
   2. If disease controlled is obtained with chemotherapy, resection of primary and secondary lesions should be considered.
4. In patients who have diffuse, metastatic CRC with unresectable metastases, modern polychemotherapy with targeted agents will offer disease control without the mortality and morbidity of surgery directed at the primary lesion.

The hypothesis of this study is that, given the dramatic improvement in response rates with current regimens incorporating oxaliplatin and irinotecan with biologics such as bevacizumab and cetuximab, systemic chemotherapy without resection of the primary tumor is a reasonable alternative to the standard approach in these patients.  This approach takes into account the morbidity and mortality associated with colectomy in these patients compared to the potential survival benefit in an incurable disease where <10% of patients survive 5 years. 

Patients  will be treated with 5-fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) plus bevacizumab. The goal is to determine if this approach leads to an increase in “major morbidity” defined as any event related to the intact primary tumor necessitating surgery or resulting in patient death. The results of this study should be very interesting and could represent a real change in thinking about how we treat primary tumors. Oncologist. 2009;14(10):963-969.

More recommendations for lymph node adequacy in CRC

The Dutch National Working Group on Gastrointestinal Cancers has recently released colorectal cancer guidelines which includes a recommendation of a minimum of 10 lymph nodes to establish a negative lymph node status.  At the same time, the group states that "determining the lymph node status of a patient requires evaluation as many lymph nodes as possible using conventional techniques." (emphasis mine

The discussion of this recommendation states that "no definitive criteria were found in the literature regarding the minimum number of examined lymph nodes.  There is no evidence to support 12 lymph nodes, as recommended by TNM." (emphasis mine)

Furthermore, they specifically do not recommend using immunohistochemistry to detect metastases or pre-treatment of mesenteric fat with GEWF-type solutions.  While using the former to detect micrometastases is not common practice, as least in the U.S., the latter is not only fairly common, if not routine in many places (mine included!).  Also, the recent literature also supports the use of these solutions to increase lymph node retrieval, although the utility of the raw node count has been questioned with the data regarding the percentage or proportion of positive:negative nodes (whole other discussion!).

MicroRNAs as a predictive marker for stage 2 colorectal cancer

This is an interesting abstract presented at the recent 2009 Association for Molecular Pathology annual meeting which is highlighted in Medscape.  Finding the magic markers that will predict which stage 2 CRC patients will progress without chemotherapy is an intense area of research, as is research into the importance of microRNAs in various diseases.

This abstract by Dr. Elizabeth Mambo et al. from Asuragen, Inc. is a small case-matched paired study but demonstrates that 11 microRNAs could potentially be prognostic for CRC recurrence.  Interestingly, they found that most microRNAs associated with CRC recurrence were downregulated but microRNA-21 and microRNA-31 were significantly upregulated compared to tumor specimens from CRC stage 2 patients who did not experience recurrence. 

I wonder which cells are exactly showing these changes given changes in the tumor microenvironment, specifically, neoangiogenic endothelial cells, myofibroblastic cells, and inflammatory cells.  I don't know much specifically about this type of testing, but I think it is a leap to assume that the test is measuring purely the carcinoma compartment of the tumor.

Still following the miRNA story. . .