Progressive plasticity during colorectal cancer metastasis

Metastasis is the principal cause of cancer death, yet we lack an understanding of metastatic cell states, their relationship to primary tumor states, and the mechanisms by which they transition. In a cohort of biospecimen trios from same-patient normal colon, primary and metastatic colorectal cancer, we show that while primary tumors largely adopt LGR5 + intestinal stem-like states, metastases display progressive plasticity. Loss of intestinal cell states is accompanied by reprogramming into a highly conserved fetal progenitor state, followed by non-canonical differentiation into divergent squamous and neuroendocrine-like states, which is exacerbated by chemotherapy and associated with poor patient survival. Using matched patient-derived organoids, we demonstrate that metastatic cancer cells exhibit greater cell-autonomous multilineage differentiation potential in response to microenvironment cues than their intestinal lineage-restricted primary tumor counterparts. We identify PROX1 as a stabilizer of intestinal lineage in the fetal progenitor state, whose downregulation licenses non-canonical reprogramming.

Changes in the multidisciplinary management of rectal cancer from 2009 to 2015 and associated improvements in short-term outcomes

AIM

Significant recent changes in management of locally advanced rectal cancer (LARC) include preoperative staging, use of extended neoadjuvant therapies and minimally invasive surgery (MIS). This study was aimed at characterizing these changes and associated short-term outcomes.

METHOD

We retrospectively analysed treatment and outcome data from patients with T3/4 or N+ LARC ≤ 15 cm from the anal verge who were evaluated at a comprehensive cancer centre in 2009-2015.

RESULTS

In total, 798 patients were identified and grouped into five cohorts based on treatment year: 2009-2010, 2011, 2012, 2013 and 2014-2015. Temporal changes included increased reliance on MRI staging, from 57% in 2009-2010 to 98% in 2014-2015 (P < 0.001); increased use of total neoadjuvant therapy, from 17% to 76% (P < 0.001); and increased use of MIS, from 33% to 70% (P < 0.001). Concurrently, median hospital stay decreased (from 7 to 5 days; P < 0.001), as did the rates of Grade III-V complications (from 13% to 7%; P < 0.05), surgical site infections (from 24% to 8%; P < 0.001), anastomotic leak (from 11% to 3%; P < 0.05) and positive circumferential resection margin (from 9% to 4%; P < 0.05). TNM downstaging increased from 62% to 74% (P = 0.002).

CONCLUSION

Shifts toward MRI-based staging, total neoadjuvant therapy and MIS occurred between 2009 and 2015. Over the same period, treatment responses improved, and lengths of stay and the incidence of complications decreased.

A phase II study of gemcitabine and cisplatin plus sorafenib in patients with advanced biliary adenocarcinomas

Background:

This study evaluated the addition of sorafenib to gemcitabine and cisplatin in biliary adenocarcinoma first-line therapy.

Methods:

Patients with advanced biliary adenocarcinomas received gemcitabine 1000 mg m⁻² and cisplatin 25 mg m⁻² on a 2 weeks on/1 week off cycle and sorafenib 400 mg twice daily. After the initial 16 patients were enrolled, the chemotherapy doses were amended in view of grade 3 and 4 hand–foot skin reaction and haematologic toxicity. Subsequently, 21 patients received gemcitabine 800 mg m⁻², cisplatin 20 mg m⁻² and sorafenib 400 mg. The primary end point was an improvement in 6-month progression-free survival (PFS6) from historical 57–77% (90% power, type I error of 10%). Pretreatment pERK, evaluated by immunostaining, was correlated with clinical outcome.

Results:

A total of 39 patients were accrued. The most common grade 3–4 toxicities noted in >10% of patients were fatigue, elevated liver function tests and haematologic toxicities including thromboemboli, hyponatraemia and hypophosphataemia. Six-month progression-free survival was 51% (95% confidence interval (CI) 34–66%). Median PFS and overall survival were 6.5 (95% CI: 3.5–8.3) and 14.4 months (95% CI: 11.6–19.2 months), respectively. No correlation was observed between pERK and outcomes.

Conclusion:

The addition of sorafenib to gemcitabine and cisplatin in biliary adenocarcinomas did not improve efficacy over historical data, and toxicity was increased.

Goblet cell carcinoid neoplasm of the appendix: clinical and CT features

PURPOSE

To describe the clinical and CT imaging features of goblet cell carcinoid (GCC) neoplasm of the appendix.

METHODS AND MATERIALS

A computer search of pathology and radiology records over a 19-year period at our two institutions was performed using the search string "goblet". In the patients with appendiceal GCC neoplasms who had abdominopelvic CT, imaging findings were categorized, blinded to gross and surgical description, as: "Appendicitis", "Prominent appendix without peri-appendiceal infiltration", "Mass" or "Normal appendix". The CT appearance was correlated with an accepted pathological classification of: low grade GCC, signet ring cell adenocarcinoma ex, and poorly differentiated adenocarcinoma ex GCC group.

RESULTS

Twenty-seven patients (age range, 28-80 years; mean age, 52 years; 15 female, 12 male) with pathology-proven appendiceal GCC neoplasm had CT scans that were reviewed. Patients presented with acute appendicitis (n=12), abdominal pain not typical for appendicitis (n=14) and incidental finding (n=1). CT imaging showed 9 Appendicitis, 9 Prominent appendices without peri-appendiceal infiltration, 7 Masses and 2 Normal appendices. Appendicitis (8/9) usually correlated with typical low grade GCC on pathology. In contrast, the majority of Masses and Prominent Appendices without peri-appendiceal infiltration were pathologically confirmed to be signet ring cell adenocarcinoma ex GCC. Poorly differentiated adenocarcinoma ex GCC was seen in only a small minority of patients. Hyperattenuation of the appendiceal neoplasm was seen in a majority of cases.

CONCLUSIONS

GCC neoplasm of the appendix should be considered in the differential diagnosis in patients with primary appendiceal malignancy. Our cases demonstrated close correlation between our predefined CT pattern and the pathological classification.

Evaluation of the derivation of human colon adenocarcinoma from Lgr5 colon stem cells

410

Background: Human colon stem cells share phenotypic hallmarks of self-renewal and proliferation that are associated with tumor cells. Lgr5 is a marker of colon stem cells and not colon differentiated cells. In mice, deletion of the adenomatous polyposis coli gene in colon stem cells but not in colon differentiated cells, rapidly gives rise to macroscopic adenomas. We investigated the role of Lgr5 colon stem cells in human colon tumors in relation to tumor cell of origin, tumor progression, tumor recurrence, and overall survival.

Methods: Using in situ hybridization, we determined the histological distribution of Lgr5 mRNA in human colon specimens at different stages of tumor development and tumor recurrence after chemotherapy. Using gene expression analysis, we analysed Lgr5 mRNA expression levels in human normal colon (n = 33), normal liver (n = 13), colon adenomas (n = 45), primary colon adenocarcinomas (n = 170), liver metastates (n = 48) and lung metastates (n = 20). We examined the correlation between Lgr5 mRNA expression, K-ras mutation status and overall survival in stage IV colon adenocarcinomas.

Results: Human normal colon Lgr5 mRNA was always expressed at basal level and restricted to human colon stem cells. In contrast, we observed an all (Lgr5(+)) or none (Lgr5(-)) expression in human colon adenomas, adenocarcinomas and liver metastases. When present Lgr5 mRNA expression was increased 3-10 fold compared to normal colon. The Lgr5 gene expression analysis provided similar results with increased expression in 66% of human colon adenomas, 62% of primary colon adenocarcinomas, 72% of colon liver metastases and 55% colon lung metastases when compared to normal colon. We have determined that 22.5% (18/80) of Lgr5(+)and 46.4% (26/56) of Lgr5(-) colon adenocarcinoma specimens have K-ras mutations. Kaplan-Meier estimates of median overall survival in Lgr5(+) and Lgr5(-) Stage IV colon adenocarcinomas were 20 months and 15 months, respectively.

Conclusions: Human colon adenocarcinomas are derived predominantly from Lgr5 colon stem cells. Lgr5(+) colon adenocarcinomas required less frequent K-ras mutation for tumor progression then Lgr5(-) colon adenocarcinomas.

No significant financial relationships to disclose.

Regional chemotherapy for unresectable primary liver cancer: results of a phase II clinical trial and assessment of DCE-MRI as a biomarker of survival

BACKGROUND

This study reports the results of hepatic arterial infusion (HAI) with floxuridine (FUDR) and dexamethasone (dex) in patients with unresectable intrahepatic cholangiocarcinoma (ICC) or hepatocellular carcinoma (HCC) and investigates dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) assessment of tumor vascularity as a biomarker of outcome.

PATIENTS AND METHODS

Thirty-four unresectable patients (26 ICC and eight HCC) were treated with HAI FUDR/dex. Radiologic dynamic and pharmacokinetic parameters related to tumor perfusion were analyzed and correlated with response and survival.

RESULTS

Partial responses were seen in 16 patients (47.1%); time to progression and response duration were 7.4 and 11.9 months, respectively. Median follow-up and median survival were 35 and 29.5 months, respectively; 2-year survival was 67%. DCE-MRI data showed that patients with pretreatment integrated area under the concentration curve of gadolinium contrast over 180 s (AUC 180) >34.2 mM.s had a longer median survival than those with AUC 180 <34 mM.s (35.1 versus 19.1 months, P = 0.002). Decreased volume transfer exchange between the vascular space and extracellular extravascular space (-DeltaK(trans)) and the corresponding rate constant (-Deltak(ep)) on the first post-treatment scan both predicted survival.

CONCLUSIONS

In patients with unresectable primary liver cancer, HAI therapy can be effective and safe. Pretreatment and early post-treatment changes in tumor perfusion characteristics may predict treatment outcome.

Use of CXCR4 as a prognostic marker for disease-specific survival and pattern of recurrence following resection of hepatic colorectal metastases

11081

Background: Expression of the chemokine receptors CXCR4 and CCR7 has been associated with metastases and poor prognosis in primary tumors but their relevance in colorectal liver metastases (CLM) is unclear. This study examines the relationship between tumor chemokine receptor expression, pattern of recurrence and outcome after resection of hepatic metastases.Methods: Eighty patients with metastases from colon or rectal primary tumors who underwent a R0 partial hepatectomy from February 2002 to April 2004 were studied prospectively. Immunohistochemical staining was performed on the formalin-fixed, paraffin-embedded tissues of hepatic metastases using antibodies specific for CXCR4, CXCL12 and CCR7. The correlation between the CXCR4, CXCL12 and CCR7 expression and clinicopathological factors was evaluated.Results: Median follow-up was 42.9 months. Positive expression of CXCR4, CXCL12 and CCR7 was seen in 49 (61%), 23 (29%) and 48 (60%) of tumor specimens, respectively. Clinical risk score greater than 2 and high CXCR4 expression were associated with a shorter disease-specific survival (DSS) and a reduced recurrence-free survival (RFS) following partial hepatectomy for CLM (p<0.05) by multivariate analysis. CCR7 and CXCL12 expression, hepatic artery infusion pump chemotherapy, systemic chemotherapy and site of primary disease did not influence DSS or RFS. Fifty-three (68%) of the patients recurred; 11 with liver only recurrences, 25 with lung only recurrences and 18 with multiple sites of recurrences. High expression of CXCR4 is associated with widespread multiple sites of recurrence ( Table ).Conclusions: CXCR4 expression in colorectal hepatic metastases adds prognostic information with regards to DSS, RFS and patterns of recurrence and may play role in clinical decision making regarding chemotherapy and surgical interventions. CXCR4 expression may also provide additional prognostic information beyond the already validated clinical risk score. [Table: see text]

No significant financial relationships to disclose.

Young age influences treatment but not outcome of colon cancer

BACKGROUND

Early age at onset is often considered a poor prognostic factor for colon cancer. The aim of this study was to determine the association between age, clinicopathologic features, adjuvant therapy, and outcomes following colon cancer resection.

METHODS

A prospective database of 1,327 surgical stage I-III colon cancer patients operated on from 1990-2001 was evaluated, and patients grouped by age.

RESULTS

Sixty-eight patients (5%) were diagnosed at age <or=40 years (younger) compared with 1,259 patients diagnosed at age >40 (older). Younger patients were more likely to have left-sided tumors (66% vs 51%, P = .02), but no more likely to present with symptomatic lesions, more advanced tumors, or have worse pathologic features. Younger patients were noted to have more nodes retrieved in their surgical specimens than older patients (median 18 vs 14, P = .001), although the numbers of total colectomies were similar in both groups. Younger patients were also more likely to receive adjuvant chemotherapy, and this was most pronounced in the stage II cohort: 39% vs 14%, P = .003. With a median follow-up of 55 months, 5-year disease-specific survival (DSS) was similar in both study groups: 86% vs 87%, but 5-year overall survival (OS) was significantly higher in the younger patient cohort (84% vs 73%, P = .001).

CONCLUSION

Younger patients undergoing complete resection of stage I-III colon cancer had DSS similar to older patients. However, younger patients had more nodes retrieved from their specimens and were more likely to receive adjuvant therapy, especially for node-negative disease. These factors may have contributed to their overall favorable outcome.

A retropective analysis of colorectal cancer in adolescents and young adults: A report from the Surgical Committee of the Children's Oncology Group

9568

Background: The genetic origin, clinical features, and prognosis of early onset colorectal carcinomas (CRC diagnosed ≤ 30 years of age) are poorly understood. To evaluate these parameters, we performed a multi-institutional review. Methods: This is a retrospective review accomplished through a survey of Children's Oncology Group Institutions. 167 patients (median age=21yrs., range 10–30 yrs.) with adequate material were reviewed. Immunostaining for mismatch repair (MMR) proteins (MSH2, MLH1, MSH6, PMS1) was performed for 119 cases with sufficient archival tumor. Survival estimates were computed using Kaplan Meier methodology and associations assessed using a log-rank test or Cox proportional hazards. Results: The overall stage of disease at presentation: 9% stage I, 16% stage II, 34% stage III, 38% stage IV, and 4% unknown. Site of origin in the colon included: 17% right, 8% transverse, 14% left, 15% sigmoid, 37% rectosigmoid or rectum, and 9% unknown. 37% of cancers were poorly differentiated and 23% had signet ring cell features. A family history of CRC was reported in 46 (40%) of 114 patients for whom data were available. HNPCC criteria (Amsterdam II) were met in only 10 of these cases. MMR protein expression was deficient in 20 of 119 evaluable cases (17%) and was correlated to HNPCC status (P<0.0001) but not to other clinical features. R0 resection was accomplished in 115 patients. Of 159 patients with follow-up data the median survival was 44 mos. (95% CI: 31–65mos.). The 1, 3, and 5-year overall survival were 81%, 54%, and 42% respectively. Variables associated with overall survival in univariate analysis included: age (p=0.02), family history of CRC (P=0.03), HNPCC status (P=0.03), stage (P<0.0001), grade (P=0.0003), and R0 status (P<0.0001). Conclusions: CRC in this age group is associated with clinical features distinct from adult CRC, including advanced stage, high grade pathology, and poor survival. The majority of cases occur sporadically, and less than 25% can be associated with HNPCC either by clinical criteria or by MMR immunostaining. Future studies should pursue more detailed molecular characterization, improved detection strategies, and better treatment to improve outcome for these aggressive cancers.

No significant financial relationships to disclose.

Pharmacodynamic case study of sunitinib/SU11248 in a gastrointestinal stromal tumor patient: Evidence toward a mechanism of effect

9526

Background: Despite abundant pre-clinical data, the mechanisms of action in humans of multi-targeted small molecule tyrosine kinase inhibitors against sarcomas remain unclear. Herein, we sought evidence from pre- and post-treatment biospies to suggest whether the primary mechanism of action of sunitinib/SU11248 is anti-angiogenic or rather a direct anti-tumor cell effect. Methods: We report data regarding a 59 year old woman with imatinib-resistant GIST who demonstrated a marked tumor response to sunitinib treatment. Her gastric primary GIST tumor was previously resected, followed by recurrence one year later. A complete remission lasting 24 months was then attained on imatinib therapy. After progression of disease, sunitinib was started at 50 mg orally per day. A major clinico-radiographic response was seen after 12 months of therapy, followed by resection. To assess the pharmacodynamic effects of sunitinib, we undertook immunohistochemical analysis of formalin-fixed tissue sampled immediately prior to treatment and just after completing sunitinib, using anti-CD117, anti-CD34, or anti-CD31 antibodies, respectively. Results: We found a dramatic effect of sunitinib on the tumor parenchyma. Whereas the pretreatment biopsy revealed viable, mitotically active, CD117+ and CD34+ tumor cells, the post-treatment specimen was >90% sclerotic and necrotic. The CD31+ blood vessels appeared robust both pre- and post-treatment. Vessel counts did not differ significantly before and after treatment by CD31 staining (3.3±2.0 per field vs. 1.8±1.3, p= 0.09). Thus, the tumor cells were largely eliminated with sunitinib treatment, while blood vessels were still present after 12 months of therapy. Conclusions: This observation supports the assertion that the mechanism of sunitinib in GIST is predominantly cytotoxic against the tumor by directly targeting KIT and that an anti-angiogenic effect, either through the VEGF-R2 in endothelium or through the PDGF-R in pericytes, may be secondary.

[Table: see text]

Small-cell carcinoma of the gastrointestinal tract: a retrospective study of 64 cases

Small-cell carcinoma (SmCC) of the gastrointestinal tract is a very rare and aggressive malignancy. To better define its clinicopathological features, the records of all patients with this disease seen at Memorial Sloan Kettering Cancer Center between 1980 and 2002 (n=64) were reviewed. The most common primary tumour locations were in the large bowel and oesophagus. Predisposing medical conditions for non-small-cell cancers, positive family cancer history, and metachronous tumours were common. In all, 37% had mixed tumour histology and 48% presented with extensive disease, according to the Veterans' Administration Lung Study group (VALSG) staging system used for small-cell lung cancer. Treatment outcome in limited disease (LD) suggested a role for surgery and chemotherapy. Platinum-based regimens resulted in a 50% response rate. The 2-year survival was 23% and two prognostic factors were identified, the extent of disease according to the VALSG system (P<0.01) and TNM stage (P=0.03). Anatomic location had no clinical impact. In conclusion, SmCC from various gastrointestinal sites can be viewed as one clinical entity. Mixed tumour histology is common and may affect therapy. Surgery, combined with chemotherapy, should be considered for LD. The value of the VALSG system was implied and possible differences from small-cell lung cancer were noted.

Neuroendocrine carcinomas of the colon and rectum

PURPOSE

This study was designed to review experience with neuroendocrine carcinomas of the colon and rectum at a single institution, with emphasis on the pathology and clinical characteristics of this uncommon malignancy.

METHODS

A study group of patients was identified from a prospective colorectal service database. Pathology was reviewed and neuroendocrine tumors were classified by a single pathologist. Medical records were retrospectively reviewed.

RESULTS

From March 1975 to September 1998, 38 patients with neuroendocrine carcinomas were identified from the colorectal service database comprising 6495 patients (0.6 percent). These neuroendocrine carcinomas did not include carcinoid tumors. Average patient age was 57 years (range, 29-86 years). There were 17 males (44.7 percent) and 21 females (55.3 percent). Tumors were located as follows: 17 colon, 14 rectum, 6 anal canal, and 1 appendix. The diagnosis of neuroendocrine carcinoma was suggested preoperatively from tissue biopsy in 59.3 percent (16/27) of patients evaluable. Pathology was reviewed and tumors were categorized as small cell carcinoma (n = 22) or large cell neuroendocrine carcinoma (n = 16). Most tumors (20/25 evaluable, 80 percent) stained positive by means of immunohistochemistry for neuroendocrine markers, including chromogranin (18/19), synaptophysin (10/15), and/or neuron-specific enolase (14/15). Metastatic disease was detected at the time of diagnosis in 69.4 percent of the patients (25/36). Tumors were advanced at the time of diagnosis, with American Joint Committee on Cancer (AJCC) Stage I (n = 6), Stage III (n = 7), and Stage IV (n = 25) tumors. As a group, these tumors had a poor prognosis, with a median survival of 10.4 months. One-year, two-year, and three-year survival was 46 percent, 26 percent, and 13 percent, respectively. There was no significant difference in survival based on pathologic subtypes. Median follow-up time was 9.4 months (range, 0.6-263.7 months).

CONCLUSIONS

Neuroendocrine carcinomas of the colon and rectum are uncommon, comprising less than 1 percent of colon and rectal cancers. Pathologically, these tumors are poorly differentiated carcinomas with distinctive cytoarchitectural features and are often immunoreactive for markers of neuroendocrine differentiation. The prognosis for high-grade neuroendocrine carcinomas is poor, as most patients have metastatic disease at the time of diagnosis.

Automated, multiplex assay for high-frequency microsatellite instability in colorectal cancer

PURPOSE

In a series of hereditary nonpolyposis colorectal cancer (HNPCC) patients, we evaluated the sensitivities of the individual microsatellites recommended by the National Cancer Institute (NCI) consensus workshop for detection of high-frequency microsatellite instability (MSI-H). On the basis of this evaluation, we developed a three-marker assay that assigns microsatellite instability (MSI) in a multiplex polymerase chain reaction.

METHODS

Individual marker sensitivity was assessed in 18 HNPCC tumors. Multiplex and NCI assays were then assessed in a series of 120 patients with early-onset colon cancer.

RESULTS

The sensitivity of microsatellite markers BAT25, BAT26, D2S123, D5S346, and D17S250 for ASI in HNPCC cancers was 100%, 94%, 72%, 50%, and 50%, respectively. The three most accurate markers were combined and optimized in a multiplex assay that assigned MSI-H whenever at least two of three markers revealed ASI. In early-onset colon cancers, the prevalence of MSI-H determined by the multiplex assay and by the NCI assay was 16% and 23%, respectively. The additional MSI-H tumors and patients with MSI-H identified by the NCI assay lacked the traits characteristic of MSI-H seen in tumors and patients identified by the multiplex assay: retention of heterozygosity (NCI additional 22% v multiplex 84%; P =.003), characteristic tumor morphology (0% v 64%; P =.006), and 5-year cancer survival rate (44% v 100%; P =.0003).

CONCLUSION

The multiplex assay identifies colon cancers with MSI-H by assessing three highly accurate microsatellite markers. This assay identifies a smaller MSI-H cohort with more homogeneous clinical features and is superior as a marker of favorable prognosis. It merits prospective evaluation as a marker of prognosis and as a screening test for HNPCC.

The founder mutation MSH2*1906G-->C is an important cause of hereditary nonpolyposis colorectal cancer in the Ashkenazi Jewish population

Hereditary nonpolyposis colorectal cancer (HNPCC) is caused by mutations in the mismatch-repair genes. We report here the identification and characterization of a founder mutation in MSH2 in the Ashkenazi Jewish population. We identified a nucleotide substitution, MSH2*1906G-->C, which results in a substitution of proline for alanine at codon 636 in the MSH2 protein. This allele was identified in 15 unrelated Ashkenazi Jewish families with HNPCC, most of which meet the Amsterdam criteria. Genotype analysis of 18 polymorphic loci within and flanking MSH2 suggested a single origin for the mutation. All colorectal cancers tested showed microsatellite instability and absence of MSH2 protein, by immunohistochemical analysis. In an analysis of a population-based incident series of 686 Ashkenazi Jews from Israel who have colorectal cancer, we identified 3 (0.44%) mutation carriers. Persons with a family history of colorectal or endometrial cancer were more likely to carry the mutation than were those without such a family history (P=.042), and those with colorectal cancer who carried the mutation were, on average, younger than affected individuals who did not carry it (P=.033). The mutation was not detected in either 566 unaffected Ashkenazi Jews from Israel or 1,022 control individuals from New York. In hospital-based series, the 1906C allele was identified in 5/463 Ashkenazi Jews with colorectal cancer, in 2/197 with endometrial cancer, and in 0/83 with ovarian cancer. When families identified by family history and in case series are included, 25 apparently unrelated Ashkenazi Jewish families have been found to harbor this mutation. Although this pathogenic mutation is not frequent in the Ashkenazi Jewish population (accounting for 2%-3% of colorectal cancer in those whose age at diagnosis is <60 years), it is highly penetrant and accounts for approximately one-third of HNPCC in Ashkenazi Jewish families that fulfill the Amsterdam criteria.

Histologic classification of tumor-infiltrating lymphocytes in primary cutaneous malignant melanoma. A study of interobserver agreement

The density and distribution of lymphocytes infiltrating the vertical growth phase of primary cutaneous melanomas has been suggested by several studies to be of prognostic significance. However, few pathologists comment on tumor-infiltrating lymphocytes (TILs), and there is the perception that the assessment of TILs is subject to great interobserver variability. We studied interobserver agreement on the categorization of TILs; 20 cases of primary cutaneous malignant melanoma with a vertical growth phase component were circulated among 3 pathologists and 3 dermatologists. For each case, TILs were classified as brisk, nonbrisk, or absent according to Clark. Only 1 pathologist (a dermatopathologist) was familiar with the classification of TILs. Observers were given written guidelines and a brief tutorial before their examination of the slides. Our results show that with little instruction, overall agreement among observers was good (kappa values, 0.6 or more), especially among pathologists (kappa values, > 0.7). Three observers had excellent agreement among each other (kappa values, > 0.75). These findings suggest that the categorization of TILs can be easily taught and can be applied with an acceptable level of reproducibility in routine diagnostic practice.