CASE N°50 – Gastrointestinal stromal tumor (GIST) of the rectum

Clinical History:

Age: 55

Sex: Male

Anorectal endoscopy: Oval hypoechoic lesion of about 13 x 10 mm, contained within the rectal wall, with probable origin in  the muscularis propria,  exophytic growth into the right seminal vesicle with which still retains a subtle cleavage plane.

Conclusions: Ampullary rectal neoplasm suspicious for GIST.

Image:

cytological speciemen: (A-F) Rectal wall, FNA

histological speciemen: (G-H)Rectal wall, biopsy

gist pan cito

 

50 composit gist

Cytological Report:

Presence of a number of aggregates of spindle cells with elongated nuclei disposition fascicular,
attributable to mesenchymal neoplasm with features of GIST

Histological Report:

Single cluster of spindle cells with cyto-histological characteristics
Compatible with gastrointestinal stromal tumor (GIST) of the rectal wall.
immunohistochemistry for DOG1 (+).

Discussions:

Gastrointestinal stromal tumor (GIST) is the most frequent mesenchymal tumor of the gastrointestinal tract.

GISTs typically present in older individuals and are most common in the stomach (60-70%), followed by small intestine (20-25%), colon and rectum (5%), and esophagus (<5%).

Until recently, GIST treatment consisted of a surgical resection followed by surveillance for metastatic disease. Chemotherapy and radiation have been ineffective.

Cytologically, GISTs occurred characteristically in closely packed cohesive tissue fragments with a high cellular density often in bloody background and often formed fascicles with parallel, side-by-side arrangements of nuclei. These findings were supported by the histologic sections in which GISTs consisted of broad bundles, interlacing fascicles, or occasionally whorls of spindle or oval cells with a high cellular density and overall basophilic appearance at low magnification.

GISTs had spindle-shaped, elongated, ovoid, round, irregular-shaped nuclei with mild to moderate nuclear pleomorphism and scant cytoplasm. The correspondence between the cytologic and histologic features was observed also at high magnification. However, it was difficult to find mitoses, a criterion to diagnose malignant GISTs, in the cytologic smears because most of the tumor cells occurred in closely packed cohesive thick tissue fragments.

Cytomorphologically GISTs show a broad morphologic spectrum but rarely a significant nuclear pleomorphism, and thus it is difficult to diagnose GISTs with a high risk of malignant behavior based on cytology alone. However, in an appropriate clinical and radiologic setting the presence of closely packed spindle or oval cells forming fascicles with parallel side-by-side arrangements of nuclei suggests GIST and its immunohistochemical features in the cell block sections are sufficient to distinguish GIST from leiomyoma or schwannoma.

References:

J Korean Med Sci 2002; 17: 353-9

Fine Needle Aspiration Cytology (FNAC) of Gastrointestinal Stromal Tumor

: An Emphasis on Diagnostic Role of FNAC, Cell Block, and Immunohistochemistry

Mi Seon Kwon, Jae Soo Koh, Seung Sook Lee, Jin Haeng Chung, Geung Hwan Ahn.

 

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