A diminutive perivascular epithelioid cell tumor in the colon

Abstract

Perivascular epithelioid cell tumor (PEComa) is a rare mesenchymal tumor. Some papers have reported that colonoscopy could be used to treat PEComa with a predominantly pedunculated polyp, whereas surgical intervention is often required for cases with submucosal-type tumors. These findings suggest that the morphology of PEComa changes dramatically with disease progression. Because of the rapid progression of PEComa, endoscopic treatment remains challenging, and early-stage PEComa morphology is not well understood. A 64-year-old man presented to our hospital for a follow-up colonoscopy after undergoing multiple polypectomies. He had a medical history of colorectal adenoma and prostate cancer. A 4-mm pale blue elevated but not pedunculated lesion was observed in the transverse colon, an area where he had not had polyps previously. Since no epithelial change was observed, the presence of a submucosal tumor, such as a gastrointestinal stromal tumor, was suspected. Cold snare polypectomy was performed, and the lesion was completely resected. Histological evaluation using hematoxylin and eosin staining identified that the submucosal tumor included thickened vascular walls and adipose tissue. Although fragmented due to significant degeneration, spindle-shaped cells staining positive for smooth muscle actin were observed within and surrounding the unstructured hyalinized tissue with calcifications. Based on these findings, the lesion was diagnosed as angiomyolipoma, a subtype of PEComa. Complete resection was confirmed by histopathology. To our knowledge, this PEComa is the smallest of any PEComa reported in the literature. Our finding provides valuable insights into the very early stage of colorectal PEComas.

Keywords: PEComa; angiomyolipoma; colon; diminutive; mesenchymal tumor.

FIGURE 1

A 4‐mm pale blue elevated but not pedunculated lesion was observed in the transverse colon. No epithelial change was observed.

FIGURE 2

Histological image stained with hematoxylin and eosin revealed the presence of unstructured hyalinized tissue with calcifications within the submucosal tumor, which was observed in approximately 60% of the lesion.

FIGURE 3

Thickened vascular walls (arrows) and adipose tissues observed in the lesion.

FIGURE 4

Although fragmented due to significant degeneration, spindle‐shaped smooth muscle actin‐positive cells were observed within and surrounding the unstructured hyalinized tissue.