A Case With a Soft Sarcoma After the Complete Cure of a Primary Malignant Tumor of the Salivary Gland Occurring at the Same Site

We report a case with a soft sarcoma after the complete cure of a primary malignant tumor of the salivary gland occurring at the same site.  The patient was a 79-year-old woman.  Concerning the present illness, she consulted a local dental clinic with a phyma on the oral floor of the left lower molar in August 1998.  The phyma was extirpated, and histopathological examination led to a diagnosis of neurofibroma.  In June 2007, she consulted our hospital with a phyma on the oral floor of the left lower molar and pain.  A histopathological diagnosis of adenoid cystic carcinoma was made in our department.  In December 2007, left supraomohyoid neck dissection and oral floor tumorectomy were performed under general anesthesia.  Histopathological examination of the resected specimen suggested primary adenoid cystic carcinoma of the sublingual gland.  In January 2008, postoperative radiotherapy was started (total radiation dose: 60 Gy).  Follow-up was conducted in our department.   In April 2013, swelling and pain were noted on the left mandibular oral floor. Detailed examination was carried out.  A fracture line was observed at the lower anterior teeth, suggesting radiation-induced mandibular osteomyelitis.  Anti-inflammatory drug therapy and follow-up were performed, but mandibular oral floor/submental swelling was noted in July 2013.   Histopathological examination was conducted, leading to a diagnosis of soft sarcoma (myogenic soft sarcoma was suspected).  PET-CT revealed a tumor involving an extensive area.  Palliative care was selected based on the patient’s wishes.  In September 2013, the patient died.  The development of soft sarcoma after the complete cure of a primary malignant tumor of the salivary gland at the same site is extremely rare.  In this article, we report such a patient and review the literature.