Histopathological approach to colorectal medullary carcinomas and their clinicopathological importance

Öz

Background and Aims: Medullary carcinomas are rare tumors, constituting less than 1% of all colorectal cancers, characterized with nongland-forming, solid sheets of malignant cells with vesicular nuclei, prominent nucleoli and abundant pink cytoplasm. They are important tumors due to their relationship with high microsatellite instability and Lynch syndrome. We reviewed the clinicopathological features of medullary carcinomas. Materials and Methods:The resection specimens of 50 poorly differentiated adenocarcinomas, examined between 2002-2011 and showing at least focal areas with a solid growth pattern, were retrospectively reviewed, re-classified, and re-staged according to the World Health Organization 2010 classification for features of medullary carcinoma. The clinicopathological findings were compared statistically with poorly differentiated adenocarcinomas using nonparametric tests.Results: Seven cases were reclassified as medullary carcinoma, constituting 0.62% of 1128 colorectal tumors diagnosed using their resection specimens within the given period. Three of the cases were female, and the mean age was 62± 5.9 years (range: 41-80 years). Tumors were located in right colon (5/7), showed expansive growth pattern (6/7), prominent Crohn's-like lymphoid reaction (5/7), and tumor-infiltrating lymphocytes (7/7). When compared with 43 poorly differentiated adenocarcinoma cases, the lower incidence of lymphovascular invasion (28% versus 39.5%), pT4 (14.3% versus 20.9%) and pN2 tumors (14.3% versus 30.2%) and absence of perineural invasion, tumor "budding" and "dirty necrosis" (p=0.002, chisquare) were noteworthy. Conclusions:Medullary carcinomas are rare tumors located predominantly in the right colon, showing an expansive growth pattern, and respectively, lower tumor and lymph node stages. They deserve special attention due to their special histological features and differential diagnostic pitfalls. The clinicopathological findings in our series are consistent with the previous literature. This study is presented to draw attention to this rare but important entity, which may have significant clinical implications in view of its relationship with Lynch syndrome.

Anahtar Kelimeler

• Colon cancer, medullary carcinoma, Lynch syndrome, histopathology

Kolorektal medüller karsinom tanısına histopatolojik yaklaşım ve klinikopatolojik önemi

Öz

Giriş ve Amaç: Medüller karsinomlar, tüm kolorektal kanserlerin %1’inden azını oluşturan, histolojik olarak geniş eozinofilik sitoplazmalı, veziküler nükleuslu ve belirgin nükleollü hücrelerle karakterli glandüler diferansiyasyonun gözlenmediği, solid büyüme paternine sahip nadir tümörler olup, yüksek mikrosatellit instabilite ve Lynch sendromu ile olan ilişkisi nedeniyle önemli antitelerdir. Çalışmamızda medüller karsinom olgularının klinikopatolojik özellikleri araştırılmıştır. Gereç ve Yöntem: Kolorektal rezeksiyon materyalleri 2002-2011 yılları arasında değerlendirilen ve odaksal olarak solid büyüme paternine sahip alanları bulunan 50 az diferansiye adenokarsinom olgusu, 2010 Dünya Sağlık Örgütü sınıflamasında tanımlanan kriterlere göre geriye dönük olarak yeniden değerlendirilmiş, evrelendirilmiş ve medüller karsinom olasılı- ğı açısından araştırılmıştır. Bulgular az diferansiye adenokarsinomlarda izlenen bulgular ile nonparametrik testlerle karşılaştırılmıştır. Bulgular: Yedi olgu medüller karsinom olarak değerlendirilmiş olup incelenen dö- nemde değerlendirilen 1128 olgu içerisindeki oranı %0,62’dir. Olguların üçü kadın, yaş ortalaması 62±5,9’dur (Dağılım:41-80). Tümörler sağ kolon yerleşimli (5/7) ve ekspansif büyüme paternine sahip olup (6/7), belirgin Crohn-benzeri lenfoid reaksiyon (5/7) ve tümörü infiltre eden lenfositler (7/7) göstermektedir. Az diferansiye adenokarsinom olarak sınıflanan 43 olgu ile karşılaştırıldığında lenfovasküler invazyon (%28’e karşılık %39,5), pT4 (%14,3’e karşılık %20,9) ve pN2 tümör oranının (%14,3’e karşılık %30,2) daha düşük olduğu; perinöral invazyon, tümör “tomurcuklanması” ve “kirli nekroz”un ise hiç olmadığı (p=0,002, ki-kare) dikkati çekmiştir. Sonuç: Medüller karsinomlar, sıklıkla sağ kolon yerleşimli, ekspansif büyüyen, göreceli olarak daha erken evrede izlenen ancak özel histolojik görünümleri ve ayırıcı tanı güçlükleri nedeniyle üzerinde durulması gereken tümörlerdir. Serimizde izlenen bulguların literatürle uyumlu olduğu görülmüştür. Çalışma, bu az görülen ancak Lynch sendromu ile ilişkisi gibi önemli klinik yansımaları olabilecek antiteye klinik duyarlılığın artırılması amacıyla sunulmuştur.

Anahtar Kelimeler

• Kolon kanseri, medüller karsinom, Lynch sendromu, histopatoloji

Kaynakça

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