A case of mixed tumour of the skin with intracardiac metastasis
Malignant mixed tumour is an exceedingly rare cutaneous adnexal carcinoma with a propensity for aggressive growth, recurrence and metastasis. More common in men (x2), it can affect all age groups (range 15 months to 50 years. ) Malignant mixed tumour usually presents as a firm, circumscribed, asymmetrical cutaneous or subcutaneous large tumour plaque between 2-15cm in diameter, with a predilection for the trunk and extremities including hands and feet. Almost 50% of all patients have local recurrences and nodal and distant metastases are observed in one third of the cases.
A 62 year old lady presented with a warm, hard tumourous plaque overlying her right scapular, 5cmx4cm. 20-years earlier the patient had developed breast cancer of the left breast and underwent mastectomy and subsequent radiotherapy. She was otherwise well and on no regular medication. MRI scanned demonstrated a 6x5x4cm soft tissue mass associated with neovascularization within the subcutaneous fat, with low T1 and high T2 signal.
Histology revealed a moderately pleomorphic spindle cell tumour with hyperchromatic nuclei and a high mitotic index (5-6 mitoses/ 10HPF). The lesion consisted of both hyper- and hypo-cellular regions. In addition, parts of the tumour was composed of cords of small epithelioid cells embedded within a myxoid stroma. Less necrotic, cellular myxoid and chondroid areas were noted. Immunostaining was positive both for S100 and AE1/AE3, but not melanA, desmin, SM actin, HHF 35, CD34 or MUC4.
The patient was initially treated with surgery followed by local radiotherapy 60GY (30fractions over 46days). Upon completion of radiotherapy, there was local recurrence. A CT thorax showed multiple pulmonary metastasis. Patient received 1st line doxorubicin, second line trabectedin, 3rd line docetaxel and gemcitabine consecutively but interval CT scans all showed disease progression after the chemotherapy. Patient also had palliative radiotherapy to the area post-chemo 20GY in 5 fractions over 7 days. Patient was switched to 4th line paclitaxel and carboplatin after not responding to all 1st-3rd line options. Patient was admitted to hospital due to tachycardia, ECHO was performed and revealed a large mass (17.1cm2) enveloped in the right ventricular free wall and the tricuspid annulus.
The most common sites for malignant mixed tumour distance metastasis are lung, bone and brain. Cardiac metastasis has not been previously described. Treatment consists of complete excision, radiotherapy and combination chemotherapy. However prognosis remains poor.