Rare histologic types of rectal cancer: A monocentric cases series report

There is paucity of data on rectal cancer with uncommon histologic types. The objective was to describe managements of care and outcomes in patients with rectal cancer of histologic types other than adenocarcinoma.

This monoinstitutional retrospective study included all patients with rectal cancer undergoing rectal radiotherapy.

From 2004 to 2015, 744 patients were treated for rectal cancer, and ten had a histologic type other than adenocarcinoma. The median age was 60.7 years (range: 34.6-80.4 years). Histologic types were neuroendocrine (four), adenosquamous (one), undifferentiated with large cell (one), clear cell (one), anaplastic with small cell (one), signet ring cell (one) and adenocarcinoma with choriocarcinomatous differentiation (one). Four patients were initially diagnosed with a stage IV rectal cancer, and two ultimately became metastatic. Six patients underwent surgery, with four neoadjuvant chemoradiotherapies. None experienced complete response and two had incomplete resections. First-line and concomitant chemotherapies were adapted to histology results, mainly with etoposide and platinum salts for neuroendocrine and small cells tumours. Four patients experienced progression before first line treatments were achieved. Median progression free survival and overall survival were 3.8 and 10.1 months respectively. Two patients were long survivors (22 and 54.7 months, both still alive). All other died of rectal cancer.

The present study highlights the rarity and the specificities of uncommon histologic types of rectal cancer. We report the real-life management and outcome of rare histologic types of rectal cancers, with dismal prognosis of stage IV tumours. We also report that treatments were adapted to histology.