Table 1

Histological and immunohistochemical differentialdiagnosis of rectal GISTinvolving prostate
Diagnosis GIST (rectum/ prostate) Leiomyoma (rectum/prostate) Leiomyosarcoma (rectum/prostate) Schwannoma (rectum/prostate) Fibromatosis (mesenteric) Solitary fibrous tumour (prostate) Malignant melanoma (rectum/ prostate)
Growth Pattern Fascicles, storiform or palisading Fascicles Fascicles Antoni A/ Antoni B Parallel fascicles, collagenous background “Patternless pattern”, collagenous background, staghorn vessels Diffuse / nested
Cell Type Spindle cell, high cellularity, no perinuclear vacuolization Spindle cell, “cigar-shaped” nuclei, perinuclear vacuolization, low cellularity Spindle cells, “cigar-shaped nuclei, atypia and intense nuclear pleomorphism, vacuolization, high cellularity Spindle cells, wavy nuclei, nuclear atypia may be present Bland spindle or strellate-cells, low to moderate cellularity Spindle cells, low or high cellularity, pleomorphism (variable) Epithelioid (rarely spindle cell)
Mitosis Few to many Few Frequent Rare Rare 0-15 / 10 HPF Frequent
Necrosis/ Hemorrhage May be present Absent Present Sometimes present Absent Variable Usually present
CD 117 Consistenly positive (cytoplasmic and membranous) Negative Negative Negative Positive sometimes (cytoplasmic) Negative Rarely positive
CD34 Consistenly positive Rarely positive Negative Sometimes focal Very rare Positive Negative
Actina (SMA) Sometimes positive Positive Positive Negative Positive Rarely Negative
Desmina Rarely Positive Positive Negative Very rare Negative Negative
S-100 Rarely Very rare Very rare Strongly positive Negative Negative Positive
HMB-45 Negative Negative Negative Negative Negative Negative Positive
Beta-Catenin Negative Negative Negative Negative Positive Negative Negative

Macías-García et al.

Macías-García et al. Diagnostic Pathology 2012 7:150   doi:10.1186/1746-1596-7-150

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