Malignant Triton tumour of labia majora- a case report

Introduction- Malignant triton tumour (MTT) is a relatively rare variant of malignant peripheral nerve sheath tumour (MPNST). It is defined as MPNST with rhabdomyosarcomatous differentiation. It is commonly located in head and neck, extremities and trunk. We report a case of Malignant triton tumour occurring in labia majora.Case scenario - A 30 year old female presented with nodules all over the body. The nodules were initially seen in the labia majora and left groin, at the time of birth. She was diagnosed to have neurofibromatosis type 1 in 2011. In view of increased itching and bloody discharge from the labia major, excision of left majora was done in February of 2013, in a general hospital. We received 7 slides and 8 blocks of that specimen for review. On microscopic and immunohistochemical examination, a diagnosis of malignant triton tumour was made. She was treated with radiotherapy in April 2013 and is disease free till date.DiscussionPrimary malignant peripheral nerve sheath tumour involving vulva is extremely rare. Approximately 15 of MPNSTs show heterologous elements such as bone, cartilage and striated muscle. Most of the reported heterologous mesenchymal components are histologically malignant. Along with the histological features, immunohistochemistry aids in the confirmation of MTT. The prognosis of the MTT is worse than that of MPNST. Leiomyosarcoma, Rhabdomyosarcoma, MFH (pleomorphic undifferentiated sarcoma) are most common differential diagnoses for MTT. These are differentiated on the basis of microscopic examination and specific immunohistochemical markers.Conclusion -Malignant triton tumour is a very rare tumour and its occurrence in labia majora is extremely rare, however should be kept in differential diagnosis, particularly in a setting of NF1, as it has worst prognosis compared to MPNST.