CyclinD1 Positive High-Grade Endometrial Stromal Sarcoma: A Fascinating Entity!

The 2014 WHO classifies endometrial stromal tumours into endometrial stromal nodule (ESN), low-grade endometrial stromal sarcoma (LGESS), high-grade endometrial stromal sarcoma (HGESS), and undifferentiated uterine sarcoma (UUS). LGESS and HGESS are histomorphologically, immunohistochemically and genetically distinct from each other. A 51-year-old postmenopausal lady presented to us with vaginal bleeding. Radiological findings revealed a well defined heterogeneous lesion involving the whole of uterus. Hysterectomy revealed a large polypoidal tumour, occupying the entire uterine cavity. Microscopically, the tumor was predominantly composed of epithelioid cells with very few intervening spindle cell areas. Immunohistochemically, epithelioid cells were diffusely positive for cyclinD1, while were negative for CD10, ER, PR. Diagnosis of cyclinD1 positive HGESS was rendered. This case highlights the importance of performing cyclinD1 immunostaining in diagnosing HGESS.


Introduction
rearranged cases show diffuse (> 70%) moderate to strong immunostaining for cyclinD1 in tumour cells. Thus they deducted that cyclin D1 can be used as a surrogate marker for identification of YWHAE-NUTM2 ESS in appropriate setting. [5] Here we present a case of HGESS, which was diagnosed based upon diffuse cyclinD1 positivity.

Case Report
A 51-year-old postmenopausal lady presented to us with history of off and on vaginal bleeding of 01 year duration. Per abdominal findings were a 12 weeks size mass which was firm, tender with smooth well defined borders.
Radiological Findings: She underwent transabdominal ultrasonography that revealed a bulky uterus measuring 11.5x10x 3 cm and showing heregenous echotexure. Right ovary was also bulky. She also underwent MRI pelvis which disclosed a well defined heterogeneous lesion involving the whole of uterus and measuring 8.3 x 5.9 x 7.5 cm. The lesion was predominantly soft with cystic areas. The lesion was extending upto uterocervical junction. Fat planes between the mass and urinary bladder were illdefined. The right adnexal mass measured 5.6 x 5.2 cm.
She underwent transabdominal hysterectomy with bilateral salpingoophrectomy. During intraoperative examination, a large uterine mass of the size of 12 weeks was noted, with extra uterine extension to right adnexa. The mass was adherent to the bladder and rectum. The mass could not be removed in toto.
Pathological Findings: Grossly, the hysterectomy specimen revealed an enlarged uterus measuring 11.5 x 10 x 3. Based upon histomorphology and immunohistochemistry, diagnosis of cyclinD1 positive high-grade endometrial stromal sarcoma (HGESS) was finally rendered. Post-operatively, the patient underwent 40Gy/28# of radiotherapy. She is presently doing well and is under follow-up.

Discussion
Endometrial stromal sarcomas accounts for approximately 0.2% of all malignant uterine tumors and 10-15% of uterine sarcomas. These tumours frequently occur in women between 40 and 55 years of age, as seen in the present case. [6] Norris and Taylor, in 1966 first classified EST into ESN, LGESS, and HGESS. [4] The subdivision into low-grade (<10 mitosis/10HPF) and high-grade(> 10 mitosis/10 HPF) was based on mitotic count. They studied necrosis and cytological atypia but found these to be prognostically not relevant. However, further studies confirmed that even mitotic count was not prognostically significant.  [8] Of the 11 YWHAE-rearranged primary uterine tumors www.pacificejournals.com/apalm eISSN: 2349-6983; pISSN: 2394-6466 described by them, 7 contained a mixture of round cell and spindle cell areas, whereas 3 and 1 showed a purely round cell and purely spindle cell appearance, respectively. The round cell component described was highly cellular, and the tumor cells were typically arranged in a vaguely nested growth pattern, with the nests being separated by a delicate stromal capillary network. The round cells were epithelioid in appearance with scant to moderate amount of eosinophilic cytoplasm, had irregular nuclear contours with inconspicuous nucleoli. These tumours showed brisk mitosis and areas of necrosis. Our case also demonstrated high -grade round cell component with characteristic nuclear features, brisk mitosis and areas of necrosis.
Immunohistochemically, the high-grade round cell component of the tumour shows diffuse strong nuclear staining for cyclinD1, lack of CD10, and weak or absent staining for ER and PR. [6] This is in contrast to LGESS which characteristically show diffuse CD10, ER, PR positivity and weak/patchy cyclinD1 staining. Our case also showed strong nuclear staining for cyclinD1 in more than 70% of epithelioid tumour cells and negative staining for ER, PR, and CD10. Spindle cell component showed CD10 positivity and cyclin D1 negativity.
YWHAE-NUTM2A/B (previously YWHAE-FMS22A/B) rearrangement needs to be confirmed by molecular tests such as reverse transcription polymerase chain reaction (RT-PCR) or fluorescence in situ hybridization (FISH) analysis. However, in limited resource settings, these tests may not be available at all the centers. In this scenario, the distinctive morphological and immunohistochemical features of HGESS are generally good surrogate markers for YWHAE-rearrangement. In fact, Lee et al observed diffuse cyclinD1 positivity in YWHAE-rearranged ESS cases with sensitivity of 100% and specificity of 99%. [5] Genetic analysis could not be performed in our case due to non-availability of the test in our laboratory.
Differential diagnosis in our case included epithelioid leiomyosarcoma, malignant perivascular epithelioid cell tumour (PEComa), undifferentiated uterine sarcoma, and undifferentiated uterine carcinoma. No conventional areas of leiomyosarcoma were seen and tumour cells were negative for SMA, desmin, and caldesmon. PEComa was excluded by absence of immunoexpression of muscle and melanocytic markers. Undifferentiated uterine carcinoma (UUC) can occur in pure form or in combination with low-grade endometrioid adenocarcinoma and show diffuse positivity for cyclinD1. However, they usually show focal/ patchy positivity for EMA/ broad-spectrum CK. In our case, no areas of low-grade endometrioid adenocarcinoma were identified despite of extensive sampling (total 15 sections studied of tumour). The tumour cells showed no immunostaining with EMA/ CK. Adequate tumour sampling is of paramount importance in the cases where UUC and HGESS are in differential diagnosis. This fact was highlighted by Shah et al, in their study of cyclinD1 expression in ten cases of UUC. [10] All the tumours showed cyclinD1 expression, with six cases showing diffuse and strong staining and four cases with patchy staining. Thus, adequate sampling and staining for EMA/broadspectrum CK cannot be overemphasized to rule out any carcinomatous component.
UUS is a high-grade sarcoma that lacks a specific line of differentiation. Histologically, these have been classified into uniform (UUS-u) and pleomorphic (UUS-p) type. [9] Out of these, UUS-u can show morphological and immunohistochemical overlap with HGESS. However, finding of CD10 positivity in UUS-u usually excludes HGESS. [4] It is important to diagnose HGESS, because these patients usually present with advanced stage disease (stages II-IV) and frequently have recurrences, usually within a few years after initial surgery. Anti-estrogenic therapy is likely ineffective given the lack of ER and PR immunopositivity in the high-grade component. Furthermore, although experience is limited, adjuvant therapy may provide survival benefit. [3]

Conclusion
In high grade uterine mesenchymal tumours showing round cell component in isolation or with spindle cell component, revealing absent CD10 immunoexpression, an extended panel of immunohistochemistry, including cyclinD1 should be added, before labelling the tumour as undifferentiated uterine sarcoma. This has prognostic as well as therapeutic implications.