Title:Epithelioid lieomyoma of uterus – a case report

Introduction

Epithelioid smooth-muscle tumors of the gastrointestinal tract have been well studied. Similar tumors of the uterus have been subject of only a few reports. Epithelioid leiomyoma are rare atypical smooth muscle tumor of the uterus.1 This entity is studied less, to quote & has many unanswered questions.

Case detail

A 65 year old post menopausal woman presented with bleeding per vagina. On examination no mass per abdomen or mass per vagina seen. Ultrasound abdomen showed a bulky uterus with fundus & body showing round hyper echoic area measuring 5.9 X 6 cm with 2 to 3 cystic areas noted. The ultrasound findings were suspicious for fibroid. Total abdominal hysterectomy with bilateral salpingo-oophorectomy was performed.

Specimen received showed solitary well circumscribed sub mucosal nodule(figure 1). Cut section of the nodule showed yellow areas with cystic spaces (figure 2). Microscopy showed polygonal cells with clear to eosinophilic cytoplasm in clusters(figure 3). Bundles of smooth muscle cells with extensive areas of hyalinization and sex cord – like pattern of arrangement of the cells were seen(figure 4). Masson Trichome stain highlighted the smooth muscle cells and collagenised areas aiding in the diagnosis epithelioid lieomyoma(EL)(Figure 5). The mean age of presentation of epithelioid lieomyoma is 48 years. Common clinical manifestion includes abnormal bleeding (36%), abdominal / pelvic pain (23%), menorrhagia (23%) and mass per abdomen (14%)1

Discussion

EL commonly presents as solitary yellow to grey mass with hemorrhagic and cystic areas. They are softer than usual leiomyomas.2 Leiomyoblastomas have single file and sheet like pattern with epithelioid cell nests, clear cytoplasmic halo and clear cell nests. Clear cell type leiomyoma have nests of clear cells. Plexifrom type leiomyoma have long anastamosing cords of small uniform cells separated by variable hyalinised stroma. Commonly mixture of above mentioned types are seen which have a common designated term as epithelioid leiomyoma. 3

Differential diagnosis include endometrial stromal tumor, pure sex cord stromal like tumors, epithilioid leiomyosarcoma and perivascular epithelioid cell tumors (PEComas)2 Presence of smooth muscles rules out endometrial stromal tumor and sex cord like tumor.2 Epithelioid leiomyosarcoma have high cellularity, necrosis and mitosis (> 5/10 HPF)2. Average age of presentation of PEcoms is 45years in contrast to epitheloid smooth muscle tumors which present at 48years.4,5 Though Epithelioid cells, Spindle cells, Giant cells, Eosinophilic cells, Stromal Hyalinization are common features for both PEcomas and epithelioid leimyoma, presence of network of capillaries are exclusively a feature of PEComa. Clear cells are commanly seen in PEComas rather than EL. At least one melanocytic marker shows 100% positivity in PEComas, and 100 % positivity for smooth muscle actin in EL cases. 4,5 Approximately 50% of the cases of PEComas and EL will show Desmin positivity. 4,5 One school of thought considers PEComa concept requires refinement, as they considerit to be a group of lesions rather than an individual disease and refutes the term PEComa for HMB-45+ epithelioid tumors of uterus.6,7 The other school of thought consider Uterine epithelioid tumor with clear cells and HMB-45 positive cases as PEComa6,7 HMB 45 is also positive in normal myometrium, non clear cells, and conventional leiomyomas.5,7 The reason for this is uncertain and it could be a true expression of gp-100 protein or cross reactivity of HMB-45 antibody with an unrelated epitope.5Epithelioid smooth muscle tumors are associated with tuberous sclerosis. 7

There are certain uncertainties in the behavioral pattern of EL. Presence of two or more following features are not well established to assess the behavior of EL.

1)Large size (>6cm)

2) Moderate mitotic activity (2-4 mitotic figures/10 HPF)

3) Moderate to severe cytological atypia.

4)Necrosis.

Hence, they are classified as uncertain malignancy and careful follow up is needed. 250% of epithelioid tumors with amitotic index of 2 to 4/10 HPF may behave in a malignant fashion8 The Nature of the margin is not predictive of outcome.8No single histological feature of epithelioid smooth muscle tumors of the uterus has predicted the metastatic potential.8

In our case the size of the tumor was 7 cms in diameter. It was encapsulated with clear cells and extensive hyalinization(Figure 6) was seen. No necrosis was observed and mitosis was 1/10 HPF.2 Hence a benign lesion was considered.

Conclusion

Rarity, less established predictive criteria for malignancy and no consensus in using IHC markers to differentiate certain entities like PEComa warrants studies with large number of cases & long term follow up.”

References:

  1. Robert J. Kurman , Henry J. Norris . Mesenchymal tumors of the uterus VI. Epithelioid smooth muscle tumors including leiomyoblastoma and clear-cell leiomyoma. A clinical and pathologic analysis of 26 cases .Cancer:1976 ; 37(4): 1853–1865.
  2. Hendrickson M.R, Tavassoli F.A, Kempson R.L, Mccluggage W.G, Haller U, Kubik-Huch R.A. Mesenchymal tumours and related lesions. In: Fattaneh A, Tavassoli F.A, Devilee P.editors. World Health Organisation classification of tumors. Pathology and genetics of tumours of breast and female genital organs. IARC Press: Lyon 2003, 233-44
  3. Silverberg.S.G, Tabbara S.O The uterine corpus. In: Silverberg S.G, DeLellis R.A, Frable W.J, LiVolsi V.A, Wick M.R. editors. Silverberg’s principle and practice of surgical pathology and cytopathology. 4th ed. Philadelphia: Churchill Livingstone Elsevier;2006, 1933-87.
  4. Oluwole Fadare. Uterine PEComa: appraisal of a controversial and increasingly reported mesenchymal neoplasm. International Seminars in Surgical Oncology 2008, 5:7
  5. Folpe AL, Mentzel T, Lehr HA, Fisher C, Balzer BL, Weiss SW. Perivascular epithelioid cell neoplasms of soft tissue and gynecologic origin: a clinicopathologic study of 26 cases and review of the literature. Am J Surg Pathol 2005; 29:1558-75.
  6. Russell Vang,Richard L.Kempson.Perivascular epitheloid cell tumor(PEComa) of the uterus. Am J Surg Pathol 2002;26(1):1-13.
  7. Silva, Elvio G ; Deavers, Michael T ; Bodurka, Diane C; Malpica, Anais . Uterine Epithelioid Leiomyosarcomas with Clear Cells: Reactivity With HMB-45 and the Concept of PEComa.American Journal of Surgical Pathology:2004 February ;28(2): 244-249
  8. Yu Sakai.Epithelioid vascular leiomyoma of the uterus mimicking Glomangiomyoma. Arch Gynecol Obstet (2007); 275:59–61