Gastrointestinal stromal tumour of the anorectum

Gastrointestinal stromal tumour more commonly occurs in the stomach.

This paper studied 133 GIST of the anorectum:

CD117	96/96
CD34	84/89 (this is a higher rate than at other sites)
SMA	7/87 (of which 6 cases were CD34 positive)
Desmin	1/80
S-100	0/80
Cytokeratin 18 (clone DC-10)	2/57
GFAP	0/53
Neurofilament	0/57

Differential diagnosis

Smooth muscle tumours	SMA and desmin positive. Most are CD34 and CD117 negative
Endometrial stromal sarcoma arising in endometriosis or spreading from the uterus	CD10 and hormone receptor positive
Schwannoma	very rare in rectum. S-100 positive. CD34 and CD117 negative.
Melanoma	S-100 and HMB-45 positive. May be CD117 positive

Prognosis

<2 cm or less in diameter and <= 5 mitoses/50 HPF	indolent; 1 of 20 had a recurrence and none had metastases
2 to 5 cm diameter and <= 5 mitoses/50 HPF	2 of 12 had recurrences plus one died of tumour
5 cm or larger OR more than five mitoses per 50 HPFs	malignant behaviour; 56/73 had recurrence, metastases or died of disease

Reference

Miettinen, M., M. Furlong, et al. (2001). "Gastrointestinal stromal tumors, intramural leiomyomas, and leiomyosarcomas in the rectum and anus: a clinicopathologic, immunohistochemical, and molecular genetic study of 144 cases." Am J Surg Pathol 25(9): 1121-33.

This page last revised 29.12.2003.

©SMUHT/PW Bishop