Suitability of the Cellient(TM) cell block method for diagnosing soft tissue and bone tumors

BACKGROUND: The diagnosis of tumors of soft tissue and bone (STB) heavily relies on histological biopsies, whereas cytology is not widely used. Cellient(TM) cell blocks often contain small tissue fragments. In addition to Hematoxylin and Eosin (H&E) interpretation of histological features, immunohistochemistry (IHC) can be applied after optimization of protocols. The objective of this retrospective study was to see whether this cytological technique allowed us to make a precise diagnosis of STB tumors. METHODS: Our study cohort consisted of 20 consecutive STB tumors, 9 fine‐needle aspiration (FNAC) samples, and 11 endoscopic ultrasonography (EUS) FNACs and included 8 primary tumors and 12 recurrences or metastases of known STB tumors. RESULTS: In all 20 cases, H&E stained sections revealed that diagnostically relevant histological and cytological features could be examined properly. In the group of 8 primary tumors, IHC performed on Cellient(TM) material provided clinically important information in all cases. For instance, gastrointestinal stromal tumor (GIST) was positive for CD117 and DOG‐1 and a PEComa showed positive IHC for actin, desmin, and HMB‐45. In the group of 12 secondary tumors, SATB2 was visualized in metastatic osteosarcoma, whereas expression of S‐100 was present in 2 secondary chondrosarcomas. Metastatic chordoma could be confirmed by brachyury expression. Two metastatic alveolar rhabdomyosarcomas were myf4 positive, a metastasis of a gynecologic leiomyosarcoma was positive for actin and estrogen receptor (ER) and a recurrent dermatofibrosarcoma protuberans expressed CD34. CONCLUSION: In the proper clinical context, including clinical presentation with imaging studies, the Cellient(TM) cell block technique has great potential for the diagnosis of STB tumors.