Unique Features Spotlighted in Calcified Chondroid Mesenchymal Neoplasm
We studied the largest cohort (33 patients) of a rare and recently described soft tissue tumor known as “calcified chondroid mesenchymal neoplasm” (CCMN) which commonly harbor FN1-gene rearrangements. Our primary goals were to investigate the morphology, radiology, and clinical behavior in hopes to aid pathologist recognition and increase awareness as most cases were sent to The Johns Hopkins Hospital by other pathologists seeking expert pathology opinion out of concern for malignancy. Our results indicate CCMN has an equal gender distribution (17 males, 16 females) and primarily affects middle-aged adults (mean age 51 years) widely throughout the body but with a predilection for hands, feet, and the temporomandibular joint (TMJ). Radiologic review showed soft tissue masses often with faint internal calcification patterns that occasionally scalloped adjacent bones but all appeared indolent/benign. Most were small (mean size 2.1 cm) and had a homogeneous fibrous/gritty tan-white cut surface on gross evaluation. Histologic evaluation demonstrated frequent multinodular architecture with prominent chondroid matrix and increased cellularity towards the periphery. Careful close inspection revealed polygonal “chondroblast” cells with eccentric nuclei and moderate cytoplasm with occasionally spindling/fibroblastic forms. Most were notable for grungy and/or lacy calcifications and a subset demonstrated osteoclast-like giant cells. Well-developed hyaline cartilage and mature bone was present in a minority. Finally, a small subset contained polarizable calcium pyrophosphate deposition disease (CPPD) rhomboid-shaped basophilic crystals (mass-forming CPPD pseudogout). Follow-up was available in 15 patients and all were without evidence of disease after simple excision. Herein, we confirm the distinct morphologic and clinicopathologic features associated with this entity with the largest series to date, focusing on practical diagnostic separation from similar chondroid neoplasms. Thus, pathologist awareness is critical in avoiding over treatment by misdiagnosis of chondrosarcoma as the behavior of CCMN appears entirely benign