[1233] Perivascular Epithelioid Cell Tumor (PEComa) of the Gynecologic Tract: A Clinicopathologic Analysis of 16 Cases Including TFE3 Rearrangement Analysis in a Subset

John K Schoolmeester, Brooke E Howitt, Michelle S Hirsch, Paola Dal Cin, Bradley J Quade, Marisa R Nucci. Brigham and Women's Hospital, Boston, MA

Background: PEComa is a family of tumors characterized by co-expression of melanocytic and muscle markers. It is often misclassified because it is rare, under-appreciated and has morphologic overlap with epithelioid smooth muscle tumors. This study, the largest to date, characterized the clinicopathologic features of PEComa arising in the female genital tract.
Design: 16 cases of gynecologic PEComa were identified in our institutional and consultation files. All were analyzed for numerous histologic and immunohistochemical features. Staining in >1% of cells was considered positive for all antibodies except TFE3 (>25% staining required). FISH for TFE3 rearrangement was performed in 3 cases. Clinical history and follow up were obtained.
Results: 13 cases were primary of the uterus, 2 of the adnexa and 1 of the vagina. 43.5% of submitting diagnoses were leiomyosarcoma or poorly differentiated uterine sarcoma. Tumors ranged from 0.3 to 15.5 (mean 7.6) cm. 3 patients DOD, 5 are AWD and 8 are AWOD (2 mo-13 yrs follow up, mean 31.2 mo). All patients with adverse outcome had histologic features defining malignancy in non-gynecologic PEComa.

Histopathologic Features
Tumor Interface (multiple patterns observed)14 infiltrative, 10 pushing, 3 endometrial stromal sarcoma-like
Nested Growth13/16 (81%)
Stromal Hyalinization9/16 (56%)
Tumor Necrosis8/16 (50%)
LV Invasion5/16 (31%)
Cell Morphology9 predominantly epithelioid (56%), 7 predominantly spindled (44%)
Dyscohesive Cells14/16 (88%)
Cytoplasmic Quality15 clear and eosinophilic (94%), 1 clear vacuolated (6%)
Melanoma-like Nucleoli10/16 (63%)
Intranuclear Pseudoinclusions6/16 (38%)
Mitotic Index (per 10 hpf)Range 0-84 (mean 29)
Mitotic Index (per 50 hpf)Range 0-395 (mean 136)

IHC Features
HMB4516/16 (100%)
MelanA14/16 (88%)
MiTF10/11 (91%)
Cathepsin K12/12 (100%)
TFE3*5/12 (42%)
SMA14/15 (93%)
Desmin14/14 (100%)
h-Caldesmon11/12 (92%)
*Three cases with TFE3 immunoreactivity were negative by FISH for TFE3 gene rearrangement.

Conclusions: Gynecologic and non-gynecologic PEComa share distinct morphologic and immunophenotypic findings. Established histologic features of malignancy appear to apply to gynecologic tumors. Although TFE3 expression was frequent, it did not correlate with gene rearrangement. Gynecologic PEComa is under-recognized and often misclassified; therefore, awareness of its appearance and immunohistochemical profile will aid in its separation from uterine smooth muscle tumors, which is essential as PEComa may respond to mTOR inhibition therapy.
Category: Gynecologic & Obstetrics

Tuesday, March 5, 2013 1:00 PM

Poster Session IV # 246, Tuesday Afternoon


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