Microscopic description and IHC:
H&E of the biopsy shows ulceration with acute and chronic inflammation, fibrosis with atypical (radiation) fibroblasts, atypical endothelial cells and hyalinized blood vessels. The atypical fibroblasts have the characteristic smudge nuclei with a preserved N/C ratio. The overlying epithelium shows regenerative type changes with focal crypt loss and distortion and large atypical cells in the lamina propria.
CMV, Adenovirus and AE1/AE3 were negative by IHC thus ruling out metastatic prostate cancer or melanoma as well as a possible infectious etiology.
Discussion:
Nearly all patients who undergo pelvic radiation have acute radiation proctitis but only 5-15% develop chronic radiation proctitis.
The ionizing radiation damages DNA, membranes and proteins resulting in proctitis within hours to days and typically resolving within two months. If progression to chronic radiation proctitis occurs then the mesenchymal tissue is most likely to be damaged. Chronic radiation proctitis can manifest months to years after radiation therapy.
Acute radiation proctitis may be subclinical but most patients suffer variably from diarrhea, pain, tenesmus, and hematochezia.
Chronic radiation proctitis may be associated with diarrhea, ulcers, pain, bleeding, stenosis, strictures, and fistulas.
Radiation proctitis risk is higher in patients with higher radiation doses, less fractionation of the dose, thinner patients, the elderly, concurrent or subsequent chemotherapy, collagen vascular disease, hypertension, diabetes mellitus.
References:
Shadad AK. Gastrointestinal radiation injury: Symptoms, risk factors and mechanisms. World Journal of Gastroenterology. 2013;19(2):185. doi:10.3748/wjg.v19.i2.185.
Sarin A, Safar B. Management of radiation Proctitis. Gastroenterology Clinics of North America. 2013;42(4):913–925. doi:10.1016/j.gtc.2013.08.004.
Schultheiss TE, Lee WR, Hunt MA, et al. Late GI and GU complications in the treatment of prostate cancer. Int J Radiat Oncol Biol Phys 1997; 37:3.
Coia LR, Myerson RJ, Tepper JE. Late effects of radiation therapy on the gastrointestinal tract. Int J Radiat Oncol Biol Phys 1995; 31:1213.