Indian Journal of Pathology and Microbiology

: 2008  |  Volume : 51  |  Issue : 1  |  Page : 76--77

Endometrial stromal nodule with smooth muscle differentiation

V Geetha, S Rupashree, SS Bhat 
 Department of Pathology, Kasturba Medical College, Manipal, Karnataka, India

Correspondence Address:
V Geetha
Department of Pathology, Kasturba Medical College, Manipal - 576104, Karnataka


Uterine tumors composed of a prominent component of smooth muscle and endometrial stroma (so-called stromomyoma) are distinctly uncommon. This article describes the morphological features of one such tumor discovered as an incidental finding in a hysterectomy specimen of a 49-year-old lady with a clinical diagnosis of dysfunctional uterine bleeding. Morphological and immunohistochemical (IHC) evaluation were performed and a final diagnosis of endometrial stromal nodule with smooth muscle differentiation was rendered.

How to cite this article:
Geetha V, Rupashree S, Bhat S S. Endometrial stromal nodule with smooth muscle differentiation.Indian J Pathol Microbiol 2008;51:76-77

How to cite this URL:
Geetha V, Rupashree S, Bhat S S. Endometrial stromal nodule with smooth muscle differentiation. Indian J Pathol Microbiol [serial online] 2008 [cited 2021 Nov 30 ];51:76-77
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Full Text


Uterine mesenchymal tumors pose many problems to the surgical pathologist in prediction of their biological behavior, i.e. whether benign, low malignant potential or frankly malignant. Differentiation of endometrial stromal and smooth muscle tumors can be done in most instances by routine light microscopic examination has not been a subject of discussion in the literature. However, highly cellular leiomyomas can be misinterpreted as endometrial stromal tumors and vice versa. The morphological features of one such lesion, an endometrial stromal nodule (ESN) is presented.

 Case History

A 49-year-old lady presented with abdominal pain and menorrhagia of 1-month duration following which she underwent total abdominal hystrectomy and bilateral salphingo-oophorectomy with a clinical diagnosis of dysfunctional uterine bleeding. Peroperatively, a diagnosis of intramural fibroid was made.

Pathological findings

Grossly, the uterus contained a well-circumscribed intramural tumor measuring 3 x 3 cm 2 which on cut section showed homogenous yellowish white soft to firm areas [Figure 1].

For light microscopy, conventional hematoxylin and eosin (H&E) stained slides were examined. The tumor showed diffuse sheets of closely packed small oval to spindle cells with bland nuclei, scant to moderate cytoplasm with indistinct cytoplasmic borders and numerous interspersed arterioles [Figure 2]. Foci of hyalinization and hypocellular areas were also noted focally. No smooth muscle differentiation or mitotic activity was identified.The tumor had a well-delineated margin and did not show infiltration into the adjacent myometrium. Immunohistochemical (IHC) stain showed desmin positivity in 50% of the tumor cells [Figure 2], inset.


The term "stromomyoma" was proposed by Tang et al. [1] to designate a peculiar uterine tumor with ultrastructural characteristics of both endometrial stromal and smooth muscle cells. They opined that these tumors developed due to differentiation of multipotential mesenchymal cells toward myoblasts and stromal cells. They further put forth an alternative explanation that both stromal cells and smooth muscle cells respond to the same stimuli resulting in simultaneous neoplastic proliferation.

Microscopically, these tumors are composed of cells resembling normal proliferative phase of endometrial stroma, with uniform nuclei, occasional mitosis, and scant cytoplasm; the cells being separated by an arborizing vascular network. Extensive hyalinization is a common feature in most of the tumors.

Oliva et al. [2] described endometrial stromal neoplasms with smooth muscle differentiation in which the latter was a minor component recognized only on IHC. Tavassoli and Norris [3] initially suggested restricting the diagnosis of combined smooth muscle - stromal neoplasm to tumors in which each component accounts for at least one-third of the tumor on light microscopy. As in the present case, various authors [4],[5] have documented prominent desmin positivity in ESN with no evidence of smooth muscle differentiation on H&E. Hence, desmin positivity alone may not be useful in differentiating ESN from smooth muscle neoplasms.

The differential diagnosis of this benign neoplasm includes low-grade endometrial stromal sarcoma (ESS) and cellular leiomyoma. The microscopic appearance of the former and ESN are identical. Infiltrative margins and distinctive growth as worm-like cords is noted in low-grade ESS where as the margins are well demarcated in ESN. Hence, extensive sampling of tumor margins and detecting vascular invasion are extremely important to distinguish the two. Cellular leiomyomas are composed of cells with spindle-shaped nuclei with a fascicular growth pattern, thick muscular-walled vessels, cleft-like spaces and show focal merging with the adjacent myometrium. [6] In our case, the tumor did not exhibit any of the above-mentioned features of a cellular leiomyoma.

Distinguishing cellular leiomyoma from ESN in a hysterectomy specimen is clinically unimportant since both are benign neoplasms cured by hysterectomy. However, differentiating the two is important in a curettage or myomectomy specimen if a spindle cell cannot be classified as of smooth muscle or stromal cell origin. In such cases, the possibility of low-grade ESS cannot be ruled out and hence need to be treated on an individual basis. A battery of immunomarkers including desmin, h-caldesmon, CD10, and inhibin may be very useful in such a scenario since cellular leiomyomas express h-caldesmon in addition to desmin while CD10 and inhibin expression is a feature of stromal cell. [5] In the present case, further expensive IHC studies were not performed since the characteristic features of the stromal cells were identified on light microscopy. The gross appearance and well-defined microscopic tumor margins further emphasized the benign nature of this lesion.

In summary, we have described an uncommon, benign mesenchymal uterine tumor, i.e. ESN with smooth muscle differentiation that needs to be distinguished from tumors with similar morphologic features, i.e. low-grade ESS and also from tumor with overlapping IHC findings, i.e. cellular leiomyoma.


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