A case of undifferentiated pleomorphic rectal sarcoma occurring after radiation exposure

Abstract

A 72 year-old man was referred to our hospital for a detailed examination of a recurrent rectal polyp. He had past histories of surgery and radiation therapy for prostate cancer at the age of 66 and endoscopic excision of a rectal polyp at the age of 70. Colonoscopy revealed a semi-pedunculated lesion surrounded by friable mucosa, which was positive under positron-emission tomography-computed tomography. Histopathological examination of the endoscopically excised polyp revealed proliferation of atypical cells, characterized by strong pleomorphic or spindle morphology, which was immunohistochemically compatible with undifferentiated pleomorphic sarcoma. We diagnosed this case as sarcoma presumably associated with radiation proctitis.

Keywords: Colonoscopy; Radiation proctitis; Undifferentiated pleomorphic sarcoma.

Fig. 1

When the patient was 70 years of age, a colonoscopy revealed a 10 mm sized semi-pedunculated lesion in the rectum

Fig. 2

The previous resected specimen contained spindle-shaped atypical cells with nuclear pleomorphism proliferating in a fascicular pattern and the horizontal and vertical margins were undetermined (a, b). Immunohistochemistry showed that the specimen was positive for vimentin (c), while AE1/AE3 (d), desmin (e), SMA (f), KIT (g) S100 (h), and melan A (i) were negative. Ki-67 showed a scattered distribution, with an index of about 20% (j)

Fig. 3

a, b When the patient was 72 years of age, colonoscopy identified a lesion that manifested as an 8 mm white, flat-elevated lesion with vascular dilation. c Magnifying endoscopy with narrow-band imaging showed dilated vessels. d Magnifying endoscopy with crystal violet staining showed that the superficial microstructure had disappeared

Fig. 4

PET–CT detected FDG accumulation with a maximum standardized uptake value (SUV max) of 2.22 in the rectum

Fig. 5

Histopathological examination revealed atypical cell proliferation with strong pleomorphism or spindle-shaped morphology, mainly in the proper mucosal layer to the submucosal layer (a). Immunohistochemistry showed that the specimen was positive for vimentin (b), while AE1/AE3 (c), desmin (d), SMA (e), KIT (f), S100 (g), and melan A (h) were negative. Ki-67 showed a scattered distribution, with an index of about 30% (i)