Answer: D

Histology: Histologic sections showed a paucicellular polypoid lesion, with scattered stellate to small round cells embedded in a fibromyxoid stroma with associated fibrin. In focal areas, the lesional cells form small clusters, cords, and gland-like structures.

Discussion:
Cardiac myxomas are the most common primary cardiac tumor. However, cardiac myxomas only represent a small fraction of all cardiac tumors, which are most frequently metastases. Cardiac myxomas typically arise in the left atrium, and form peduculated or polypoid lobulated masses. Histologically, they have abundant fibromyxoid stroma, although areas of hemorrhage or cystic degeneration may be seen. The neoplastic cells are stellate to round and may form small clusters or glandular structures. These cells label positively for vascular immunostains (CD31 and CD34) and calretinin. Additionally, the glandular cells may label for cytokeratins.
Cardiac myxomas are most frequently sporadic. However, they may be seen in the setting of Carney’s complex, an autosomal dominant multiple neoplasia syndrome conferring an increased risk for cardiac and extra-cardiac myxomas, psammomatous melanotic schwannomas, multiple lentigines, epthelioid blue nevi, large cell calcifying sertoli cell tumor (LCCST), and pituitary adenomas. It is also associated with endocrine over reactivity such as primary pigmented nodular adrenocortical disease (PPNAD). Mutations in protein kinase A regulatory subunit 1 alpha (PRKAR1A) have been identified in both sporadic and familial cases of Carney complex.
Although benign, cardiac myxomas may behave in a clinically aggressive or “malignant” fashion where fragments of the tumor may detach and embolize to the brain and/or other sites, or the tumor mass itself may cause cardiac outflow obstruction.

Butany J, Nair V, Naseemuddin A, Nair GM, Catton C, Yau T. Cardiac tumours: diagnosis and management. Lancet Oncol. 2005 Apr;6(4):219-28. Review. PubMed PMID: 15811617.