PMC7685769_01
(a): Biopsy prior to abdominoperineal resection showed a spindle cell proliferation, with bland nuclei and eosinophilic cytoplasm and inconspicuous nucleoli (haematoxylin and eosin stain). (b): Biopsy prior to abdominoperineal resection showed a spindle cell proliferation, with bland nuclei and eosinophilic cytoplasm and inconspicuous nucleoli. The stain for Cytokeratin AE1/AE3 was negative, which favoured the mesenchymal nature of the neoplasm. (c): Staining for CD117 and CD34 was diffusely positive, thus favouring a gastrointestinal stromal tumour. Confirmation with DOG-1 was not performed in the biopsy.
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figure1
She was referred to the National Cancer Institute with a pathology report of rectal GIST (Figure 1).
(a, b, c): Axial T1-weighted MR and Axial, Sagittal and Coronal T2-weighted MR respectively showed a large isointense mass in T1, iso-hyperintense in T2, with well-defined edges located in the pelvic region. The posterior and right lateral walls of the median and lower rectum were involved, attached to the mesorectum and levator ani muscle with a predominantly exophytic component and an intraluminal component. MR showed a tumour mass compressing and displacing the rectum to the left and the uterus superiorly. No lymphadenopathy was observed. (d). Post-contrast Axial Fat-Suppressed T1-weighted MR shows a solid component of the mass-enhanced heterogeneously.
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figure2
No metastatic disease was found (Figure 2).
(a): Surgical specimen of extra elevator abdominoperineal resection. (b): Tumour on lower rectum with well-defined edges and predominantly exophytic component. (c): Macroscopically, the tumour was a fleshy, tannish-brown, multilobular, well-circumscribed mass of 8.0 x 7.0 x 6.5 cm, centred in the muscularis propria of the rectum with ulcerated mucosa.
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Pelvic examination under anaesthesia showed a tumour at 3 cm from the anal verge with a wide base depending on the right and posterior walls of the rectum (Figure 3).
Immunohistochemical staining for CD117 was positive and specific DOG-1 was diffusely positive.
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Immunohistochemistry showed DOC-1 (+) and CD117 (+) (Figure 4).