A Rare Case of Osseous Metaplasia in Canine Leiomyoma and Plasticity of Smooth Muscle Cell

Metaplasia is a transformation of one mature cell type to other kinds of mature cells. Metaplasia is hardly detected in benign tumors, whereas it is frequently observed in malignant tumors. In this study, we report the first case of osseous metaplasia in canine leiomyoma. The region of osseous metaplasia was highly eosinophilic and had various sizes of distinct lacunae. The osseoid material was confirmed by Von Kossa staining. Except for the osseous metaplasia, the mass presented typical features of leiomyoma without any histopathological features of malignancy. The characteristics of malignant tumors, including pleomorphism, mitotic figures, and lymphatic metastasis were not identified and the mass was proven to be a benign tumor. The osseous metaplasia in leiomyoma without dysplastic changes might be due to plasticity which is a unique feature of smooth muscle cells, whether the tumor is malignant or not. This case suggests the possible occurrence of osseous metaplasia in leiomyoma, which has been overlooked due to the lack of reports. Also, it is recommended to pay attention to making a diagnosis of smooth muscle tumor with metaplasia so as not to be confused with leiomyosarcoma and leiomyoma variants.

CT characteristics of uterine and vaginal mesenchymal tumours in dogs

OBJECTIVES

To describe the CT characteristics of uterine and vaginal mesenchymal tumours in dogs and to discuss imaging findings of the tumour types encountered.

MATERIALS AND METHODS

Retrospective study on female dogs with confirmed histological diagnosis of uterine and vaginal mesenchymal tumours and available CT images.

RESULTS

120 records obtained through a medical record search were manually evaluated for eligibility, and 11 dogs presenting masses associated with the genital tract were identified. Of these 11 dogs, 7 dogs met the inclusion criteria and were included in the study. A clear degree of overlap was present between measurements of maximal diameter of benign and malignant tumours; however, malignant neoplasms tended to occupy a larger portion of the pelvic canal. Objective measurements of length suggest that malignant tumours were longer than benign forms. Bone involvement was only observed with malignancy.

CLINICAL SIGNIFICANCE

Although CT is likely to play a limited role in the advanced workup of uterine and vaginal mesenchymal neoplasms, CT may represent a more accessible diagnostic tool than MRI and results of this study may help imagers familiarise themselves with their appearances.

Regression of a vaginal leiomyoma after ovariohysterectomy in a dog: a case report

An 11 yr old female mixed-breed Siberian husky was presented with a history of sanguineous vaginal discharge, swelling of the perineal area, decreased appetite, and lethargy. A single, large vaginal leiomyoma and multiple mammary tumors were diagnosed. Mastectomy and ovariohysterectomy were performed. The vaginal leiomyoma regressed completely after ovariohysterectomy. This is the first reported case of spontaneous regression of a vaginal leiomyoma after ovariohysterectomy in a dog.