| Keywords
Leiomyosarcoma, Gastrointestinal Stromal
Tumor, Rectum, Internal Anal Sphincter, Needle Aspiration
Introduction
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A 68 yr male was referred in for a rectal
mass.
Methods for EUS Capture
EUS was done with an Olympus GFUM30 radial
endoscope using water filled technique, scanning at 7.5 and
12 MHz and with a Pentax Linear Array FG32UA endoscope at
scanning at 7.5 MHz. Images were captured to SVHS tape, digitalized
and converted to .jpg format using Adobe software.
Case/Body
- A 68 yr man presented to his physician
for rectal bleeding and constipation.
- He had been previously healthy,
with his only medical problems being hyperetension and "hemorrhoids".
His only previous surgery was a tonsilectomy.
- Medications included atenolol and
hydrochlorothiazide.
- His physical exam revealed a healthy
man of 198 lbs. All findings were unremarkable other than
a digital rectal exam which revealed a firm mass in the
posterior rectal vault.
- The patient was evaluated by colonoscopy
and EUS, with both radial and linear examinations being
performed.
- Video endoscopy revealed a large
mass which appeared to be entirely submucosal. Figure 1
shows the antegrade view, and Figure 2 the retrograde view.
- Radial EUS identified a 6 x 6 cm
hypoechoic mass with a hyperechoic focus. The tumor was
adjacent to but distinct from the prostate (figure 3). A
representative image from the visible human database is
shown in figure 4. On EUS inspection of the anal canal,
the mass could be seen either arising from, or involving
the hypoechoic layer 4, the internal anal sphincter (Figure
5).A corresponding image from the visible human database
is shown in Figure 6.
- No unusual lymph nodes were seen.
- Needle aspiration of the mass was
performed with a Mediglobe 22 g needle. Cytology demonstrated
a mesenchymal tumor with nuclear atypia, suspicious for
leiomyosarcoma.
- The tumor was removed en-bloc using
an abdominal-perineal approach. It measured 6 x 5.5 x 4.5
cm. Light microscopy revealed a spindle cell, smooth muscle
tumor with 2-5 mitoses per high power field. Immunostaining
was positive for both CD34 and CD117. No involved lymph
nodes were found. The final diagnosis was a low grade malignant
gastrointestinal stromal tumor.
- The patient did well following
his surgery and is without evidence of metastasis or recurrance
18 months after his initial resection.
Discussion / Summary Statement
Rectal leiomyoma/leiomyosarcomas (now referred
to as gastrointestinal stromal tumors, or GIST) are rare lesions
of varying malignant potential. These tumors are often 1-2
cm in size, although they sometimes fail to present until
they are quite large (1). GIST are ideal for EUS evaluation,
to assess tumor characteristics, potentially determine histology
and to help determine therapeutic options. Endosonographic
findings can be used to help differentiate malignant from
benign GIST (2,3). Features suggesting malignancy include
size greater than 3 or 4 cm, irregular outer margin, abnormal
lymph nodes, echogenic foci, and cystic spaces. The use of
needle aspiration has been shown to increase the diagnostic
capability of EUS by differentiating histology in various
types of submucosal tumors (4). Our case had some of the endosonographic
criteria for malignancy (size, hyperechoic foci), but also
had needle aspiration in which dysplastic cells were recovered,
further suggesting low grade malignancy.
The effectiveness of surgical therapy of
GIST is dependent on both the aggresiveness of the tumor (malignant
or benign) as well as extent/location (anal sphincter or pelvic
structure involvement). For low grade tumors, local excision
with or without additional therapy may be useful (5,6). However,
the local relapse rate is quite high for the more malignant
tumors, and an aggressive surgical approach is warranted (5,6).
A recent advance in the therapy of GIST
involves the use of a tyrosine kinase inhibitor against surface
KIT (CD 117), known as Gleevec (Imatinib mesylate, STI 571).
Response rates of up to 80% have been reported in preliminary
studies (7). This exciting advance in the therapy of GIST
suggests that, in the future, therapy could be developed which
could downstage tumors, perhaps allowing a less aggressive
surgical approach.
In summary, EUS should be the staging procedure
of choice for rectal GIST as it supplies essentially all of
the information required for determining the type and extent
of local therapy.
References
1. Eriguchi,N, Aoyagi,S, Hara,M, Tanaka,E,
and Hashimoto,M A case of giant leiomyosarcoma of the
rectum Kurume Med. J. 45:137-141, 1998
2. Chak,A, Canto,MI, Rosch,T, Dittler,HJ, Hawes,RH, Tio,TL,
Lightdale,CJ, Boyce,HW, Scheiman,J, Carpenter,SL, Van Dam,J,
Kochman,ML, and Sivak,MV,Jr Endosonographic differentiation
of benign and malignant stromal cell tumors Gastrointestinal
Endoscopy 45:468-473, 1997
3. Palazzo,L, Lamdi,B, Cellier,C, Cuillerier,E, Roseau,G and
Barbier,JP Endosonographic features predictive of benign
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46:88-92, 2000
4. Matsui,M, Goto,H, Niwa,Y, Arisawa,T, Hirooka,Y, and Hayakawa,T
Preliminary results of fine needle aspiration biopsy histology
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5. Yeh,CY, Chen,HH, Tang,R, Tsai,WS, Lin, PY, and Wang, JY
Surgical outcome after curative resection of rectal leiomyosarcomas
Dis Colon Rectum 43:1517-1521, 2000
6. Grann,A, Paty,PB, Guillen, JC, Cohen,AM, and Minsky, BD
Sphincter preservation of leiomyosarcoma of the rectum
and anus with local excision and brachytherapy Dis
Colon Rectum 42:1296-1299, 1999
7. van Oosterom AT, Judson I, Verweij J, Stroobants S, Donato
di Paola E, Safety and efficacy of Imatinib (STI571) in
metastatic gastrointestinal stromal tumours: a phase I study.
Lancet 358:1421-3, 2001
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