Reticulin meshwork : a potential parameter in risk assessment of gastrointestinal stromal tumors (GISTs)‎

Abstract EN

Objective: The purpose of this study was to review our series of Gastrointestinal Stromal Tumors (GISTs) and to shed more light on the reticulin meshwork patterns to investigate the question of any possible correlation between its meshwork and the biologic behavior of these tumors.

Methods : our series included 59 spindle cell tumors retrieved from the Pathology Department files at Damascus University, Assad University Hospital between 2000 and 2006.

CD 117 (c-Kit), CD 34, PS 100, and Desmin were applied.

The reticulin stain was then applied on the CD117-positive-cases.

Results : Thirty five cases showed immunoreactivity for CD117 (cytoplasmic positivity with membranous enhancement) and considered KIT-positive-GISTs (incidence rate : 5 cases / year), of which 18 cas.

51.3 % showed neural differentiation, and one 2.85 % showed dual differentiation.

The patients ranged in age from 19 to 83 years (mean 53 years with) a slight male predilection.

The most common site of GIST localization was the stomach followed by the small intestine.

The most common histologic type was the spindle cell followed by the epithelioid and mixed types.

The clinic pathologic, histologic and immunophenotypic features were reviewed with emphasis on the predictors of GISTs’ biologic behavior.

The tumor size ranged from 0.6 to 35 cm (mean 12.3 cm).

More than 80% of cases were in the high and intermediate risk groups.

No correlation was noted between neural differentiation and malignancy or between the extents and intense of CD 117 positivity and malignancy.

In the reticulin stain three special patterns of reticulin meshwork were observed : (1) the very low and low risk cases were found to be reticulin rich and had fibers encircling the single tumor cells and small groups of cells (identified in 6 of 6 cases or 100 %) ; (2) the intermediate risk cases had fibers enveloping larger groups of cells giving an alveolar-like appearance (identified in 9 of 9 cases or 100 %) ; and (3) the high risk cases had areas devoid of reticulin fibers surrounding cells with the meshwork destroyed totally (in 12 of 20cases or 60 %), or focally with adjacent foci of the intermediate risk, widely meshed pattern (in 8 of 20 cases or 40 %), a morphology that may reflect varying malignant potential in different tumor areas.

Conclusions : our findings indicate that the conditions in the reticulin meshwork considered are very predictive in risk assessment of GISTs (proportion between the paucity of fibers and malignancy).

Immunoreactivity for the CD117 epitope expressed on KIT, have improved the accuracy of GIST diagnosis.1 There are many prognostic features for GISTs ; the two most important indicators are the tumor size and mitotic index (2002 consensus approach).2 According to this approach, all GISTs have malignant potential.

Recently, anatomic location has been found to affect the risk of disease recurrence and progression so it was included in the 2007 updated criteria of the National Comprehensive Cancer Network (NCCN).

An early study indicated that the paucity of reticulin fibers is one of the features that may predict the aggressive behavior in gastric GISTs.4 The purpose of the present study was to review our series of GIST tumors and shed more light on the reticulin meshwork patterns as a suggestive feature of biologic behavior.