Loss of succinate dehydrogenase B immunohistochemical expression distinguishes pulmonary chondromas from hamartomas

Abstract

Aims Pulmonary chondromas, which are rare cartilaginous neoplasms that often arise in the setting of Carney triad, are morphologically similar to pulmonary hamartomas, which are much more common. There is evidence that succinate dehydrogenase (SDH) deficiency drives neoplasia in patients with Carney triad, and SDHB immunohistochemistry can be used as a surrogate marker to detect SDH deficiency. The aim of this study was to investigate the utility of SDHB immunohistochemistry in distinguishing pulmonary chondromas from hamartomas. Methods and results Immunohistochemistry for SDHB (clone 21A11AE7) was performed on histological sections from six cases of pulmonary chondroma and 33 cases of pulmonary hamartoma. SDHB expression was retained in all 33 pulmonary hamartomas, and lost in the majority of evaluable chondromas (five of six). Of the five patients with chondromas showing SDHB loss, four had definitive Carney triad. Most patients with pulmonary hamartomas were older males with small solitary masses, whereas chondromas often presented as multiple masses in young females. Conclusion Loss of SDHB immunohistochemical expression can be useful for differentiating pulmonary chondromas from hamartomas, and potentially identifying patients with Carney triad.

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“…However, recognition of any other mesenchymal elements or the typical invaginated bronchial epithelium favours hamartoma, as chondromas are usually composed of pure hyaline cartilage and have a fibrous pseudocapsule instead of invaginated bronchial epithelium. Immunohistochemistry for succinate dehydrogenase complex iron sulphur subunit B (SDHB) could be performed if chondroma is considered in the differential diagnosis, especially if multiple lesions are present, as Carney‐associated chondromas can have abnormal loss of expression 49 . Metastatic sarcoma, either metastatic chondrosarcoma or metastatic myxoid sarcoma, may also be considered depending on the appearance of the tumour.…”

“…However, the differentiation from hamartoma can be more difficult on small biopsies that contain only hyaline cartilage. When in doubt, immunohistochemistry for SDHB could be considered, which is often lost in Carney‐associated chondromas, as mentioned above 49 . Otherwise, a descriptive diagnosis (‘mature hyaline cartilage neoplasm’) with a differential diagnosis of chondroma versus hamartoma is appropriate.…”

“…Immunohistochemistry for succinate dehydrogenase complex iron sulphur subunit B (SDHB) could be performed if chondroma is considered in the differential diagnosis, especially if multiple lesions are present, as Carney-associated chondromas can have abnormal loss of expression. 49 Metastatic sarcoma, either metastatic chondrosarcoma or metastatic myxoid sarcoma, may also be considered depending on the appearance of the tumour. However, hamartomas have much less atypia than is typically observed in sarcoma.…”

“…When in doubt, immunohistochemistry for SDHB could be considered, which is often lost in Carney-associated chondromas, as mentioned above. 49 Otherwise, a descriptive diagnosis ('mature hyaline cartilage neoplasm') with a differential diagnosis of chondroma versus hamartoma is appropriate. Metastatic chondrosarcoma may be considered, but generally would show a much more significant degree of cytological atypia (as discussed above in the hamartoma section).…”