FH deficient uterine leiomyomas-a case series.

Introduction: Fumarate hydratase (FH) deficient uterine leiomyomas account for only 0.4 % of all uterine leiomyomas. They are characterized by some distinct histological features and may be associated with Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome. Methods: Herein we present a series of five cases of FH deficient uterine leiomyomas in patients with a mean age of 30 years. All five patients underwent myomectomy. Three of these cases had an outside histopathologic diagnosis ranging from Smooth muscle tumor of uncertain malignant potential (STUMP) to Leiomyosarcoma while two cases were operated at our centre. All five cases were reported as suggestive of FH deficient leiomyomas and were advised germline testing along with genetic counselling. Results: Immunohistochemically four of the cases showed moderate to strong positivity for 2-SC with a complete loss or reduced expression of FH while one case showed absence of 2-SC staining. Discussion: Mutations in FH lead to reduced enzyme activity and accumulation of fumarate leading to a complete loss or aberrant reduced expression seen on immunohistochemistry, which confirms the diagnosis. It is important to differentiate it from a leiomyosarcoma or other malignant spindle cell tumors as these tumors follow a benign course. Their association with HLRCC also needs to be established for a suitable follow up since HLRCC-associated RCCs are often aggressive. Conclusion: Management of such leiomyomas is myomectomy or hysterectomy with advice of genetic testing to rule out HLRCC. Histomorphology and immunohistochemistry are imperative for a correct and timely diagnosis.