Metastatic malignant soft tissue myoepithelioma: a case report showing complete response after locoregional and systemic therapy
A 61-year-old male patient with no particular previous illnesses was diagnosed with a well-differentiated STMM of the plantar surface of the second toe of the right foot, with infiltrated margins after excisional biopsy. Microscopically, myoepithelioma consists of nests and cords of epithelioid, plasmacytoid or spindle cells, with inconspicuous nucleoli, mainly eosinophilic cytoplasm and, in some cases, clear cells. The cells are embedded in a chondromyxoid, collagenous or hyalinized stroma; no significant nuclear pleomorphism is usually observed and mitoses are scarce. The malignant variant is exclusively recognized by its histological features, showing a marked cytologic atypia, prominent nucleoli, necrosis and a high mitotic index (>7/10 HPF) [, ]. The patient underwent computerized tomography (CT) of the chest and abdomen for staging; the results were normal. Considering the residual disease in the previous excision of the nodule, the patient underwent a radical disarticulation of the toe 20 days after excisional biopsy. Three months later, the patient presented a lump on the plantar surface of the third toe of his right foot, a subcutaneous nodule on the right ankle and another nodule on the back of the foot; excisional biopsy of the latter showed de-differentiated STMM. Because of these findings, a positron emission tomography-CT (PET-CT) [] was performed, which showed the presence of in-transit metastases in the right lower limb, extending to the middle third of the thigh. Ultrasound-guided fine needle aspiration cytology (FNAC) was performed at the level of the most accessible of these lesions, which confirmed secondary STMM (Fig. ). The patient was then treated with hyperthermic isolated limb perfusion (HILP) using human recombinant tumor necrosis factor 1 mg and melphalan 90 mg. During the subsequent follow-up, a complete response was documented (Figs. and ).\nFourteen months after the removal of the primary tumor, a pelvic magnetic resonance imaging (RMI) identified the presence of lymph nodes highly suspicious for malignancy in the right groin region. FNAC confirmed the presence of metastases from STMM and a complete surgical dissection of the inguinal-iliac-obturator lymph nodes was performed. The histological report documented the presence of metastases from differentiated STMM at the inguinal and iliac lymph nodes. During the following months, the patient was followed up clinically and radiologically, and all examinations were negative.\nTwenty-two months after the removal of the primary tumor, pathologic non-lymphatic nodules at the inguinal and iliac areas were noticed and initially treated with cisplatin plus doxorubicin, but concomitant pelvic progression was ascertained. Afterwards, three cycles of ifosfamid in continuous infusion (14 g/mq in 14 days every 28 days) and radiotherapy (50.4 gray in 28 fractions to the inguinal-iliac-obturator region and one boost of 64.8 gray into the area where the recurrences were found) were administrated with complete response. Currently, 36 months from the original diagnosis, the patient is alive and in good health, and undergoes follow-up examinations every 4 months.