Primary Small Cell Malignancies of the Breast: Are They Rare Malignancies?

In contrast with the other organs such as the lung, small cell tumors have been less studied in the breast due to their relatively less frequency. Although rare, neuroendocrine neoplasms, some lymphomas, and some small cell sarcomas such as undifferentiated small round cell sarcoma and rhabdomyosarcoma can be seen in small cell morphology in the breast. Many cytological specimens such as fine-needle aspiration biopsies and touch imprint cytology are used for diagnosis and further prognostic/predictive marker determination in primary breast masses, sentinel and axillary lymph nodes, and metastatic masses. Lobular carcinoma deserves to be considered in the small cell tumor group because of its small, monomorphic, discohesive, scant cytoplasmic cytological features. Since so many different types of tumors in the breast can have small cell characteristics, they should be divided into small cell neuroendocrine tumors and small cell nonneuroendocrine tumors. When evaluating small cell breast tumors cytologically, wide tumor diversity should be kept in mind, and clinical, hematological, and radiological features should be taken into consideration.

Usefulness of SS18-SSX antibody as a diagnostic marker for pulmonary metastatic synovial sarcoma

Background The novel SS18-SSX fusion-specific antibody is reported to have high sensitivity and specificity for the diagnosis of primary synovial sarcoma (SS), which often metastasizes to the lung. Thus far, no study has validated the diagnostic efficacy of SS18-SSX antibody for pulmonary metastatic SS. Therefore, we aimed to investigate the usefulness of the SS18-SSX antibody in the diagnosis of pulmonary metastatic SS. Methods We evaluated the immunohistochemistry of SS18-SSX fusion-specific antibody (E9X9V) in 10 pulmonary metastatic SS cases and the corresponding five primary sites (four limbs and one mediastinum) in five patients, for whom SS was already diagnosed and confirmed by fluorescence in-situ hybridization in the metastatic and primary sites, and in 93 clinical and histologic mimics including 49 non-SS, pulmonary metastatic sarcomas, 39 primary lung cancers, and five intrathoracic solitary fibrotic tumors. All specimens were surgically resected at Shinshu University Hospital during 2001–2019. For primary and metastatic SS, we also evaluated SS18-SSX immunohistochemistry using needle biopsy and touch imprint cytology specimens from the primary site. Results SS18-SSX staining was diffusely-strongly positive in all 10 pulmonary metastatic SS cases and the corresponding five primary sites; whereas, it was negative in all 93 clinical and histologic mimics (100% sensitivity and 100% specificity). Further, SS18-SSX staining was also sufficiently positive in the biopsy and cytology specimens. Conclusions Immunohistochemistry of the SS18-SSX fusion-specific antibody is useful for the differential diagnosis of pulmonary metastatic SS in clinical practice. This simple and reliable method has the potential to replace traditional genomic tests. However, further studies are warranted in this regard.

Usefulness of SS18-SSX antibody as a diagnostic marker for pulmonary metastatic synovial sarcoma

Background The novel SS18-SSX fusion-specific antibody is reported to have high sensitivity and specificity for the diagnosis of primary synovial sarcoma (SS), which often metastasizes to the lung. Thus far, no study has validated the diagnostic efficacy of SS18-SSX antibody for pulmonary metastatic SS, and this is the first study to report these findings. We aimed to investigate the usefulness of the SS18-SSX antibody in the diagnosis of pulmonary metastatic SS. Methods We evaluated the immunohistochemistry of SS18-SSX fusion-specific antibody (E9X9V) in 10 pulmonary metastatic SS cases and the corresponding five primary sites (four limbs and one mediastinum) in five patients (SS diagnosis of was already confirmed by fluorescence in-situ hybridization in the metastatic and primary sites), and in 93 clinical and histologic mimics including 49 non-SS, pulmonary metastatic sarcomas, 39 primary lung cancers, and five intrathoracic solitary fibrotic tumors. All specimens were surgically resected at Shinshu University Hospital during 2001–2019. For primary and metastatic SS, we also evaluated SS18-SSX immunohistochemistry in needle biopsy and touch imprint cytology specimens from the primary site. Results SS18-SSX had stained diffusely strong in all 10 pulmonary metastatic SS cases and the corresponding five primary sites without staining of SS18-SSX in all 93 clinical and histologic mimics (100% sensitivity and 100% specificity). SS18-SSX had sufficiently stained in the biopsy and cytology specimens. Conclusions Immunohistochemistry of the SS18-SSX fusion-specific antibody is useful for the differential diagnosis of pulmonary metastatic SS in clinical practice. This simple and reliable method can replace traditional genomic tests.