Endometrial Osseous Metaplasia

Author Information
Gwendolyn Fernandes*, Asmita Patil**, PY Samant*** SV Parulekar****
(* Associate Professor, Department of Pathology, ** Senior Resident, *** Additional Professor **** Professor and Head, Department of Obstetrics & Gynecology, Seth GS Medical College & KEM Hospital, Parel, Mumbai, India.)

Abstract

Osseous metaplasia of the endometrium is a rare condition characterized by the presence of mature or immature bone in the endometrium. Most cases present with secondary infertility following an abortion or chronic endometritis, some patients are asymptomatic, while others have menstrual irregularities or menorrhagia. We present two cases of osseous metaplasia of the endometrium.

Introduction

Osseous metaplasia of the endometrium is a rare condition characterized by the presence of mature or immature bone in the endometrium. Most cases present with secondary infertility following an abortion or chronic endometritis, some patients are asymptomatic, while others have menstrual irregularities or menorrhagia. Ultrasound examination showing characteristic hyperechogenic pattern of osseous tissue within the uterus helps suspect the diagnosis. The final diagnosis is confirmed by hysteroscopy and removal of the bony tissue by curettage. Complete removal of the bony spicules from the endometrial cavity by hysteroscopy under ultrasonic guidance usually cures the patient.

Case Report 1

A 24 year old woman presented with secondary infertility for 8 years. She had had a spontaneous abortion at 4 months of amenorrhea 8 years ago, at which time she had undergone a blunt curettage. Since then she had had menorrhagia, the bleeding lasting for 8 to 10 days every 30 days. Her general and systemic examination revealed no abnormality. Her uterus was of 6 weeks' size, smooth and firm. There was no pelvic tenderness or mass. Her hemogram, blood sugars, liver and renal function tests, HIV, VDRL and her husband's semen analysis reports were within normal limits. Difficulty was encountered during passage of a uterine sound and bony spicules were seen in the endometrium during hysteroscopy. All the bony spicules were removed by a sharp curette under laparoscopic control to prevent uterine perforation. She made an uneventful recovery. Her menorrhagia was cured. Three months later she was lost to follow up, and her fertility status remains unknown.


Figure 1 – Microphotograph showing mature bone surrounded by blood clot, fibrinous material and inflammatory cells.


Figure 2 – Microphotograph showing higher magnification of the bony tissue.


Figure 3 – Microphotograph showing well-formed mature bone, calcific material and inflammatory cells.

Case Report 2

A 35 year old para 4 MTP 1 presented with abnormal uterine bleeding (irregular menses with soakage of 2 pads per day) for 4 years. She had had 4 normal deliveries followed by a medical termination of pregnancy at 3 months of amenorrhea 4 years ago. Her general and systemic examination revealed no abnormality. Her uterus was of normal size, smooth and firm. There was no pelvic tenderness or mass. Her hemogram, blood sugars, liver and renal function tests, chest radiograph and electrocardiogram were normal. Endometrial aspiration showed no malignant cells. Her ultrasonography showed a 2.9 cm sized calcified lesion, which was interpreted as either endometrial calcification or calcified submucosal leiomyoma. During dilatation and curettage, there was difficulty in passage of a uterine sound. Presence of bony spicules in the endometrium was suspected. These spicules were removed held by a long, curved, hemostat, followed by curettage. She made an uneventful recovery. Her menorrhagia was cured without any additional treatment.


Figure 4 -  Microphotograph showing calcified bone and inflammatory cells.


Figure 5 – Microphotograph showing abundant calcific material and mature bone.


Figure 6 – Microphotograph showing higher power view of the mature bone.

Discussion

Osseous metaplasia of the endometrium is a rare condition characterized by the presence of mature or immature bone in the endometrium.[1] Its estimated incidence is 3/10000, there being about eighty cases described in the literature.[2] It has been referred to by various names ectopic intrauterine bone, heterotopic intrauterine bone, endometrial ossification etc.[3]
Clinically the patients are in the reproductive age group. A history of a previous pregnancy or abortion has been reported in more than 80% cases.[,3,4,5] The interval between the antecedent pregnancy and detection of endometrial ossification varies from 2 months to 14 years.[6] In our cases, it was 8 and 4 years respectively. Most cases present with secondary infertility following an abortion or chronic endometritis, some patients are asymptomatic, while others have menstrual irregularities or menorrhagia.[5,7] One of our patients had secondary infertility and the other had menorrhagia. Ultrasound examination showing characteristic hyperechogenic pattern of osseous tissue within the uterus helps suspect the diagnosis. The final diagnosis is confirmed by hysteroscopy and removal of the bony tissue by curettage.
There have been various controversies regarding the etiology and pathogenesis of osseous metaplasia of the endometrium. There have been debates on whether the osseous tissue was of maternal or fetal origin. However genetic analysis of the osseous tissue, and comparison with the DNA of both the parents, have shown that there is no male paternal genetic material in it, ruling out a fetal origin. There have been many theories of its origin, such as dystrophic calcifications and ossification of post-abortive endometritis, heterotopia, metaplasia in healing tissue, metastatic calcification, and prolonged estrogenic therapy after abortion.[3,4,5,8,9]  The most accepted theory of the origin of the osseous tissue is metaplasia of endometrial stromal cells into osteoblastic cells which produce the bone.[6] Inflammatory conditions like endometrial tuberculosis, chronic endometritis, and pyometra, trauma of curettage or instrumentation are causes of chronic inflammatory pathology and these can result in endometrial osseous metaplasia.[6] In India, endometrial tuberculosis should be ruled out as a cause of infertility as well as endometrial calcification and ossification.
It is also important for pathologists to avoid making an erroneous diagnosis of malignant mullerian tumor on histology.[5,6,7] This nonneoplastic etiology should not be missed.
Osseous metaplasia is a treatable condition. Complete removal of the bony spicules from the endometrial cavity by hysteroscopy under ultrasonic guidance usually cures the patient.[6,10,11]

References

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Citation

Fernandes G, Patil A, Samant PY, Parulekar SV Endometrial Osseous Metaplasia. JPGO 2014 Volume 1 Number 8. Available from:  http://www.jpgo.org/2014/08/endometrial-osseous-metaplasia.html