PMC8643248_01
Pelvic MRI of the tumor showing a large retrorectal cystic mass with solid mural nodule. A sagittal T2 weighted pelvic MRI (a) demonstrated a large predominantly cystic mass (*) which is anterior to the sacrum and coccyx (green arrow) and posterior to the rectum (red arrow). An unenhanced fat suppressed T1 weighted axial image (b) and a gadolinium enhanced fat suppressed T1 weighted axial image (c) demonstrated an enhancing nodule (blue arrow) in the posterior portion of the mass.
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Pelvic magnetic resonance imaging (MRI) revealed a 17.3 x 11.4 x 7.7 cm retrorectal cystic mass with solid mural nodule (Figure 1).
Microscopic examination of the cyst wall revealing squamous epithelium (a), mature bone (b), smooth muscle (c), respiratory epithelium (d), pancreatic tissue (e), and enteric epithelium (f).
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Microscopic examination of the tumor showed squamous epithelium (ectoderm), mature bone, smooth muscle (mesoderm), respiratory epithelium, pancreatic tissue, and enteric epithelium (endoderm) (Figures 2(a)-2(f)).
Proliferating glandular structures with interspersed vasculature (a); cellular atypia was appreciated at 40X magnification (b). Immunostains of the atypical glandular epithelium were positive for CK7 (c) and CDX2 (d). The Ki67 proliferative index was high (e). The p53 was wild-type (f).
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Noticeably, the tumor also demonstrated foci of proliferating glandular structures with interspersed vasculature (Figure 3(a)); cellular atypia was appreciated at high magnification (Figure 3(b)). Immunostains showed the atypical glandular epithelium to be positive for CK7 and CDX2 (Figures 3(c) and 3(d)) and focally positive for CK20, suggestive of enteric/colonic differentiation. Despite a high Ki67 index (Figure 3(e)), the histology of the tumor lacked definite evidence of malignancy and the p53 was wild-type (Figure 3(f)). In comparison to the patient's previous excision (Figures 3(a) and 3(b)), these findings showed a similar histology but with a greater degree of nuclear atypia and definite invasive architecture.
Pelvic MRI 13 months later with a sagittal T2 weighted image (a) and an axial T2 weighted image (b) demonstrated a T2 hyperintense mass within the posterior wall of the low rectum (red arrow) and multiple additional T2 hyperintense perirectal masses (black arrow).
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This was confirmed on a follow-up MRI of the abdomen and pelvis (Figure 4).
Microscopic examination of the recurrent tumor showing invasive, moderately differentiated adenocarcinoma. The tumor cell islands displayed an infiltrative pattern at 10x magnification (a), with marked structural and cellular atypia demonstrated at 40x magnification (b). The malignant glands showed a high proliferative index on Ki-67 (c), while p53 was wild-type (d).
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Permanent sections of the lesion revealed invasive, moderately differentiated adenocarcinoma (Figure 5), arising from the preexisting sacrococcygeal teratoma. The tumor cell islands displayed an infiltrative pattern at low magnification (Figure 5(a)), with marked structural and cellular atypia appreciated at high magnification (Figure 5(b)). The malignant glands showed a high proliferative index on Ki-67 (Figure 5(c)), while p53 was still wild-type (Figure 5(d)).