Cellular leiomyoma: A rare variant of uterine fibroids with an unusual presentation

INTRODUCTION

Uterine leiomyomas are non-epithelial mesenchymal benign monoclonal tumors of the uterine myometrium.¹ They are the most common tumors of the female genital tract, arising from the neoplastic transformation of single myometrial smooth muscle cells.² Clinically, they are reported to be diagnosed in over 40% of females over the age of 40 years and are detected in about 77% of uteri removed at hysterectomy.¹ They are the most common reason for gynecological consultations in women in Nigeria and other sub-Saharan African countries.²

Uterine leiomyomas develop as genetically abnormal clones of cells originating from a precursor cell where the mutation occurred.¹ Multiple myomas do not belong to the same clone; each develops independently.¹ They occur more frequently in nulliparous women, in those who are obese, in Blacks, and in women deficient in vitamin D.^2,3 There is also a hereditary predisposition.² Their growth is dependent on the ovarian steroid hormones; hence, they are rare before menarche and tend to atrophy after menopause.⁴

Cellular leiomyomas (CL) are very rare variants of uterine leiomyomas.⁵ They have been defined by the World Health Organization as a variant of leiomyoma having significantly greater cellularity than the surrounding myometrium but with clinical behavior identical to conventional leiomyoma.⁵ We hereby present the first case of a CL encountered in our setting and discuss our experience with its management. The rarity of this clinical condition, its very unusual presentation, and appearance in our practice stimulated this report.

CASE REPORT

A 69-year-old postmenopausal grandmultiparous widow presented in our private medical facility with abdominal distention of 2 weeks’ duration. The abdominal distension was gradual and was associated with urinary frequency, urgency, weight loss, and constipation. Her last childbirth was 23 years prior to presentation, and she was 16 years postmenopausal. She was a known hypertensive and was taking her antihypertensives regularly.

Examination revealed an ill lady who was mildly pale and cachectic. The abdomen was moderately distended and tense, with a positive shifting dullness. It was difficult to assess the intra-abdominal organs and exclude the presence of any intra-abdominal masses due to the tenseness of the abdomen.

On vaginal examination, the cervix was deviated anteriorly, and the posterior vaginal fornix was occupied by a soft mass that appeared to be continuous with a 14-week-sized uterus. There were no adnexal masses.

Packed cell volume, urea, creatinine, electrolytes, fasting blood sugar, liver function test, chest X-ray, and electrocardiography did not reveal any abnormality. A midstream urine culture revealed heavy growth of E. coli, for which she received a 10-day course of levofloxacin based on the organism’s sensitivity.

An abdominopelvic ultrasound scan showed moderate clear ascitic fluid within the peritoneal cavity, involving both flanks and extending into the pelvic cavity. No intrabdominal mass or para-aortic lymphadenopathy was demonstrated [Figure 1]. The uterus was bulky, lobulated in outline, heterogeneous in echotexture, and measured 12.0 cm × 8.7 cm × 9.2 cm. There were a few oval-shaped, varying-sized, ill-defined, and hypoechoic intramural and subserous masses seen within the uterine substance, distorting the normal endometrial-myometrial sonographic architectural pattern of the uterus. Both ovaries were normal in size and outline [Figure 2].

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Figure 1:

Ultrasound scan showing ascitic fluid.

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Figure 2:

Ultrasound scan showing the uterine mass.

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An abdominopelvic CT scan revealed a fairly large, fairly homogenous, rounded pelvic mass measuring 9.4 cm × 8.5 cm × 8.5 cm, which could not be delineated from the uterus. There was associated massive dense ascites, and the intra-abdominal organs were all normal.

A tentative diagnosis of a malignant disease of the uterus was entertained, probably uterine sarcoma, to exclude adenocarcinoma.

At laparotomy, the abdomen was entered via a midline sub-umbilical incision. There were about 2 L of amber-colored ascitic fluid, from which 10 mL was sent for cytology. The uterus was enlarged to 14 weeks’ gestational size and was soft with no obvious fibroid nodules. Both ovaries were atrophic. A total abdominal hysterectomy and bilateral salpingo-oophorectomy were then performed.

When bisected, the enlarged uterus, which weighed 400 grams, had a white solid mass in the center that measured 10 cm × 9 cm × 4 cm. The endometrium was not appreciated, and there were no obvious fibroid masses or nodules with overlying pseudo-capsules [Figure 3].

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Figure 3:

The enlarged uterus with a solid central mass devoid of endometrium.

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Her postoperative period was satisfactory and uneventful. She was transfused with two units of packed cells and discharged on the 7th postoperative day. In the follow-up clinic 6 weeks later, she had no complaints, her wound had healed well, and her clinical condition was satisfactory, as all her symptoms had subsided.

Histology sections showed a well-circumscribed benign mesenchymal neoplasm composed of moderate to marked cellular bundles and fascicles of spindle-shaped cells arranged haphazardly within a fibrocollagenous stroma. The cells had abundant eosinophilic cytoplasm and monomorphic, cigar-shaped nuclei. The cell lacked atypia, there was no tumor cell necrosis, and mitosis was scanty, confirming uterine CL [Figure 4].

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Figure 4:

Histology of the cellular myoma. Hematoxylin and eosin, 40x.

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Cytology of the ascitic fluid showed extensive areas of eosinophilia devoid of any epithelial or mesenchymal cells.

DISCUSSION

The various subtypes of uterine leiomyoma identified in the literature include usual or conventional leiomyomas, leiomyomas with bizarre nuclei, mitotically active leiomyomas, hydropic leiomyomas, apoplectic leiomyomas, leiomyomas with lymphoid infiltration, lipo-leiomyomas, dissecting (cotyledonoid) leiomyomas, and parasitic leiomyomas.⁶ Others are leiomyoma with skeletal muscle differentiation, epithelioid (clear cell) leiomyoma, diffuse leiomyomatosis, intravenous leiomyomatosis, benign metastasizing leiomyoma, and cellular leiomyoma.⁶

Cellular leiomyoma of the uterus is one of the histological subtypes that is rarely diagnosed (<5% of cases).¹ They are reported to have a distinct clinical phenotype compared to typical leiomyomas and are benign, uncommon variants. Though the majority are asymptomatic, the most frequent symptoms are documented to be menstrual abnormalities, pelvic mass, abdominal pain, and pelvic pressure.⁷

To further highlight the rarity of CL, particularly in our setting, a search of available literature revealed only one publication from Nigeria. This was a retrospective review of cases of uterine leiomyomas in Southwest Nigeria over 5 years, and out of 192 cases, CL constituted <1%.⁶ Though uterine leiomyomas are particularly much more predominant in Sub-Saharan Africans, in whom they occur at a much younger age, tend to develop earlier, grow much larger, and cause more severe symptoms,^2,3 it appears that when compared to the Caucasian population, where CL accounts for <5% of uterine fibroids,¹ their prevalence in blacks is very low.

Our case, though rare, was also unusual and hence interesting. Uterine fibroids are documented to be rare in postmenopausal women (<2%) due to the reduction in estrogen secretion due to loss of ovarian function, which typically occurs at menopause.⁴ Our patient, a 69-year-old grand multiparous lady who was 16 years postmenopausal, presented with a short time of onset of symptoms, massive ascites, a smooth, enlarged, soft uterus, constipation, and weight loss. These are all features of malignant disease of the uterus.⁸ In addition, the absence of well-circumscribed, firm, whorled uterine tumors with distinct pseudocapsules that demarcate them from normal myometrium, making them easy to enucleate, which are typical of conventional uterine leiomyomas,⁹ and the absence of an endometrium further heightened the suspicion of a malignant disease.

As typified by our case, CL is difficult to detect clinically and with imaging. Its diagnosis is only made after microscopic examination of a postoperative specimen.¹ Cellular myomas are significantly more cellular than normal myometrium but lack nuclear atypia, tumor cell necrosis, or increased mitotic activity. The cells are small and round to spindle-shaped.¹⁰

Management of CL depends on the clinical picture, histopathology, and the patient’s reproductive wishes. Our patient had a total abdominal hysterectomy and salpingo-oophorectomy because she was postmenopausal and had completed her family. Following treatment, CL is reported to have a favorable long-term prognosis.¹⁰

CONCLUSION

Cellular leiomyoma of the uterus, a benign and rare variant of conventional uterine leiomyoma, can present with features of malignant disease in postmenopausal women. Awareness of this rare clinical condition, a high index of suspicion among clinicians, and histological examination of relevant surgical specimens are crucial in ensuring its accurate diagnosis and effective management.