A 35-year-old woman diagnosed with mixed endometrial stromal and smooth muscle tumour of the uterus
Due to its rarity and unknown histogenesis, mixed endometrial stromal and smooth muscle tumour (MESSMT) of the uterus has received little attention. Endometrial stromal cells and smooth muscle cells share a Müllerian-mesodermal origin and are closely related. Some researchers have proposed the existence of pluripotent cells capable of differentiating into stromal cells and smooth muscle cells, among other things, during the histogenesis of a mixed endometrial stromal and smooth muscle tumour of the uterus. Other researchers considered the tumour to be a variant of endometrial stromal tumour (EST), with prominent smooth muscle differentiation, rather than a true composite tumour. ESTs can exhibit morphologic variants or unusual features such as sex cord-like differentiation, smooth muscle differentiation, fibrous or myxoid changes, granular eosinophilic or rhabdoid features, and skeletal muscle differentiation.
A 35-year-old woman (gravida 0, para 0) presented with 2 months of menorrhagia. Transvaginal ultrasonography revealed an enlarged uterus with a mass and cystic degeneration in the uterine posterior aspect. Magnetic resonance imaging revealed a well-defined intramural mass with heterogeneous signal intensity and enhancement on T2-weighted images. As a result, rather than a uterine sarcoma, a degenerative leiomyoma was suspected. The patient had no significant medical or gynaecological history, and her menstrual cycle was regular. She was not using oral contraceptives when she was admitted, and she was a nonsmoker who drank socially. CA 125 and CA 19-9 serum levels were measured. Squamous cell carcinoma antigen levels were within normal limits. Other laboratory findings, such as haemoglobin levels, were within normal limits.
The patient had an abdominal mass removed. There were no other tears on the surface of the resected specimen, which was relatively well dissected. A well-circumscribed soft mass measuring 6.56.0 cm was revealed by the cut surface. The mass was yellowish in colour and appeared as an intracystic nodule in the mass’s centre. The tumour was composed of three morphologically distinct components. The outermost area, for example, was composed of a fascicular proliferation of monotonous spindle cells with eosinophilic cytoplasm and cigar-shaped nuclei, indicating smooth muscle differentiation. There was no evidence of nuclear atypia or necrosis in these tumour cells.
There were a few signs of mitoses found (3/10 high-power fields) (HPFs])
On gross examination, the mass’s central area consisted of cells with round-to-ovoid nuclei, inconspicuous nucleoli, and scant cytoplasm with indistinct cell borders within small tubules and a cord-like arrangement. There was a prominent hyalinized stroma with numerous small blood vessels. This component resembled an ovarian sex-cord tumour morphologically. There was no necrosis, but there were some mitotic figures (7/10 HPFs). The areas in the middle between the two components described above were made up of well-differentiated endometrial stromal cells with only minor nuclear atypia. Furthermore, no necrosis or mitosis was observed.
The interface with the smooth muscle differentiation showed a distinct but focally irregular and infiltrative boundary. Pathologically, these findings were consistent with low-grade endometrial stromal sarcoma. There was no evidence of lymphovascular tumour invasion in any of the mass components.
The immunohistochemical staining results clearly distinguished each of the three components. Smooth muscle cells in the outermost region were positive for SMA and desmin but negative for CD10. SMA, desmin, and CD10 were all found in the central region. CD10 was only found on well-differentiated endometrial stromal cells.
Source: American Journal of Case Reports