Pleomorphic (giant cell) carcinoma revisited: A historical perspective and conceptual reappraisal

The term pleomorphic "giant cell" carcinoma was coined by Sommers and Meissner in 1954 for a pancreatic carcinoma variant showing a "sarcoma-like transformation" and characterized by an admixture of undifferentiated cells with striking variation in size and shape. Based on the predominant cell type, four patterns were recognized: spindle cell (sarcomatoid), pleomorphic "giant cell", osteoclastic giant cell-rich, and anaplastic round cell. These four basic patterns frequently coexisted within same tumor, albeit to a significantly variable extent. Follow-up series further characterized the entity, expanded its topographic distribution to include almost all organ systems, and illustrated its morphological and phenotypic homology among different organs. Although resemblance of the neoplastic cells to rhabdomyoblasts was already pointed out by Stout in 1958, the term "rhabdoid" (introduced in 1978 for specific kidney tumors) was not used for carcinomas until 1993. Review of the old and recent literature indicates pleomorphic "giant cell" carcinoma is not an entity but a morphological pattern in the spectrum of undifferentiated (anaplastic) and sarcomatoid carcinoma that can originate in any organ, either in a pure form or as a dedifferentiated carcinoma component. These tumors fall into two major categories: a monomorphic (variable admixture of small or larger "gemistocyte-like" rhabdoid cells and epithelioid cells) and a pleomorphic (bizarre large polygonal, spindled, or multinucleated malignant cells) subtype. The few available genetic studies suggest close association of the monomorphic type with SWI/SNF pathway defects, while bizarre-looking pleomorphic tumors usually harbor complex and heterogeneous genetic alterations. Most tumors dominated by the pleomorphic "giant cell" pattern are extremely aggressive, resulting in death, soon after diagnosis, irrespective of treatment modalities. This review gives an historical account on the evolution of the pleomorphic "giant cell" carcinoma concept with special reference to their relationship to SWI/SNF complex alterations.