Abstract
We report a unique case of juvenile rectal polyp occurring in a 15-year-old male which showed osseous (bony) metaplasia on histological examination. The phenomenon is striking on histological examination but it appears to have no clinical significance.
INTRODUCTION
Osseous metaplasia occurring in various types of polyps in the stomach, colon, etc. has been described in multiple case reports. It is definitely a striking morphological feature but has not been shown to have any clinical significance. We report a case of a rectal polyp occurring in a 15-year-old male which showed this rare histological feature.
CASE REPORT
A 15-year-old boy from Multan presented to the Gastroenterology Clinic with complaints of bleeding per rectum for the last 3 months. Colonoscopic examination revealed a solitary polypoid lesion in the upper rectum measuring 1×0.8 cm in diameter. It was reddish in colour and had a slightly irregular surface. Except for mild erythema in the rectum and sigmoid, the rest of the colonoscopic examination was unremarkable.
BIOPSY
We received the specimen in the Section of Histopathology, Aga Khan University coded as a “rectal polyp” with a query of villous adenoma.
On gross examination a single dark brown polypoidal piece of tissue measuring 1×0.6 cm in diameter was seen. No stalk was identified. It was submitted in total for histopathological examination. On microscopy a polypoidal lesion was seen with an extensively ulcerated surface. It was composed of cystic and dilated crypts filled with neutrophils and inspissated mucin. Foci of osseous metaplasia were seen composed of mature bony trabeculae (figs 1 and 2). The lamina propria showed oedema along with acute and chronic inflammatory cells. Features of adenomatous polyps including dysplasia were not seen. The case was reported as a juvenile rectal polyp with foci of osseous metaplasia.
Figure 1.
Section showing cystically dilated crypts with inspissated mucin and multiple bony trabeculae. H&E, ×10.
Figure 2.
Higher magnification view showing mature bone formation. A cystically dilated crypt with mucin is seen on the right and neutrophilic exudate is seen on the left. H&E, ×20.
DISCUSSION
Osseous metaplasia has been described in various types of polyps as well as in mucin-producing tumours in the stomach, colon, etc. These include adenomatous, hyperplastic and hamartomatous polyps. Multiple case reports are present in the literature which describe this morphological curiosity which has no clinical significance. Cavazza et al1 described osseous metaplasia in a tubulovillous adenoma. Groisman et al2 reported two cases of osseous metaplasia occurring in a tubulovillous adenoma and a juvenile rectal polyp, respectively. Ohtsuki et al3 reported metaplastic bone formation in a gastric hyperplastic polyp.
Haque et al4 reported four cases of metaplastic bone formation in the gastrointestinal tract. One of their cases occurred in Barrett’s oesophagus, while the remaining three cases were mucin-producing tumours of the appendix, transverse colon and rectum.
LEARNING POINTS
The pathogenesis of osseous metaplasia in gastrointestinal tract polyps and tumours is unclear, but it has no clinical significance (figs 1 and 2).
Mucin extravasation is believed to be a constant feature, and it is important that the presence of bone in biopsies from mucinous tumours of the gastrointestinal tract should not be misinterpreted as bone invasion.4
Footnotes
Competing interests: none.
Patient consent: Patient/guardian consent was obtained for publication.
REFERENCES
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