Pleomorphic adenoma is the most common neoplasm of the major salivary glands, and can undergo malignant transformation to carcinoma ex-pleomorphic adenoma (CXPA) in untreated patients.

Our case describes a 56-year-old male with a 15-year history of slowly growing expansive right-sided neck. He underwent excision of the neck mass, neck dissection, and pectoralis flap reconstruction. Final pathology revealed a 22 cm CXPA with myoepithelial and salivary duct carcinoma components. The patient was recommended radiation therapy to receive 66 Gy in 33 fractions.

CXPA is rare, typically aggressive, and carries a poor prognosis. This case is unique given the location of the tumor arising from the submandibular gland and delayed presentation leading to its massive size. Surgical planning for a lesion of this nature is complex due to structures in the vicinity and additional needs for reconstruction. Another important consideration highlighted by this case includes the need to assess patient reliability and provide resources to reduce the odds of being lost to follow up and enhance patient care.

True malignant mixed tumors, also known as salivary gland carcinosarcoma (SCS), are uncommon yet highly aggressive lesions associated with a poor prognosis. These tumors exhibit a distinctive biphasic structure characterized by both epithelial and mesenchymal components. Recent research has shown that the majority of SCS cases stem from pre-existing pleomorphic adenomas (PAs), suggesting a stepwise developmental pattern. In this report, we present a case of a 73-year-old female with SCS and describe the clinical, radiographic, and pathologic observations. Notably, the SCS was associated with a residual PA. The SCS displayed a CTNNB1::PLAG1 gene rearrangement, providing a molecular basis for its origin from the PA. Further DNA genomic analysis exposed mutations in BAP1, PER1, and LRPB1. Our findings provide support to the theory that SCS emerges from a pre-existing PA while highlighting the multiple genetic changes that could contribute to malignant transformation.

Carcinosarcoma ex pleomorphic adenoma is a rare malignant neoplasm, with most cases reported in the parotid gland. We herein report a case of a 75-year-old male referred to our hospital with a long-standing right parotid lesion that was treated in an outside hospital by a superficial parotidectomy. The patient reported a painful, rapidly enlarging mass following the excision. Histopathological examination showed the proliferation of malignant epithelial and mesenchymal elements with a solid sheet of Langerhans cells admixed with eosinophils. The Langerhans cells were reactive to CD1a and BRAF; hence, a diagnosis of carcinosarcoma ex pleomorphic adenoma with Langerhans cell histiocytosis was given. Complete clinical and radiographic workup showed no other organ involvement. The patient underwent total parotidectomy with adjuvant chemoradiation; however, the tumor progressed and showed lung metastasis. We herein report the first case of a concurrent Langerhans cell histiocytosis with associated carcinosarcoma ex pleomorphic adenoma.

Carcinosarcoma ex pleomorphic adenoma (CCPA), also known as true mixed malignant tumor, is an extremely rare high-grade aggressive tumor. The histopathologic examination is the gold standard for diagnosis and radiologic imaging also plays an important role. CCPA should be considered in the differential diagnosis of salivary gland tumors when there are findings suggestive of malignancy such as necrosis and diffusion limitation on imaging.

Carcinosarcomas of the salivary gland are rare neoplasms and have been described arising de novo or in association with pleomorphic adenoma (PA). PLAG1 and HMGA2 translocations are known to occur in PAs and carcinomas ex PA but are mutually exclusive.

We report a case of a carcinosarcoma in the parotid gland of a 77-year-old man with unusual anaplastic sarcomatoid giant cell morphology.

Microscopically, a small separate PA was found adjacent to the carcinosarcoma. By conventional notion, the PA and carcinosarcoma would be considered related, as carcinosarcomas are well known to arise from PAs (carcinosarcoma ex PA). However, fluorescence in situ hybridization (FISH) assay demonstrated PLAG1 translocation in the carcinosarcoma and HMGA2 translocation in the separate PA.

These findings support that the carcinosarcoma likely originated from another PA with a PLAG1 translocation or de novo but not from the coexisting PA harboring a different translocation. To our knowledge, the case is the first to demonstrate PLAG1 translocation by FISH in a sarcomatous component of any parotid gland tumor, which may help better classify these tumors. In addition, multiple PAs are commonly found in the salivary gland, and to our knowledge, our case is the first to demonstrate that the same parotid gland can host PAs and PA-related tumors with different translocations.