. Author manuscript; available in PMC: 2020 Nov 1.

Published in final edited form as: Abdom Radiol (NY). 2019 Nov;44(11):3581–3594. doi: 10.1007/s00261-019-02045-9

Table 6.

Important features of uncommon rectal tumors on imaging.

Tumor type	Imaging features

NET	Superficial submucosal mass
	Smaller than 1 cm
	Intense contrast enhancement

Melanoma	High SI on T1WI (rectal lesion and lymph node)
	Very low in the rectum
	Less perirectal desmoplasia

GIST, leiomyosarcoma and leiomyoma	Submucosal mass, may have peritoneal or liver mets, without nodal metastases
GIST, leiomyosarcoma and leiomyoma	Endophytic/exophytic configuration for GIST
	Well circumscribed lesion
	Without local invasion
	No lymphadenopathy
	Larger lesions may be heterogeneous
	Radiological differentiation is difficult

Angiosarcoma	Irregular wall thickening
	Heterogeneous enhancement
	Prominent vessels

Lipoma	High SI on T1WI and T2WI
	Signal loss on fat-suppression sequences

Lymphoma	Heterogeneous high SI on T2WI
	Homogeneous intermediate SI on T1WI
	Mild to moderate enhancement
	Often large without obstruction

Hemangioma	Very high SI on T2WI
	Progressive enhancement
	Vascular engorgement/changes in perirectal fat from increased vascularity
	Phleboliths (better seen on CT)