Routine histological examination of epidermoid cysts; to send or not to send?

- Epidermoid cysts are common but malignant transformation extremely rare.
- Good association between a clinical diagnosis and a final pathology diagnosis of epidermoid cyst.
- Intra-operative transection of resected specimen may improve confidence in diagnosis.
- Where classical features are present clinically and on excision, the specimens do not require histological examination.

BackroundThe diagnosis of epidermoid cyst is seldom in doubt, and associated malignancy extremely rare, yet it is commonplace for the lesion to be sent to the pathology laboratory for analysis. The aim of this study was to evaluate our current practice with regards to diagnostic accuracy among clinicians, and assess risk of not routinely sending suspected epidermoid cysts for histological examination. Potential cost savings were also estimated and calculated.MethodsRetrospective analysis of clinical and pathology data on all suspected epidermoid cysts excised from a Scottish district general hospital over a 5-year period between January 2011 and October 2015.ResultsFive hundred and thirty-six suspected epidermoid cysts were excised during the study period. Three hundred and ninety-six were sent for histological examination which confirmed a diagnosis of epidermoid cyst in 303 (76.5%) cases. There was good agreement between preoperative suspicion and final histological diagnosis: 80.8% (257/318) among referring clinicians, 81.9% (289/353) among reviewing surgeons, and 88.4% (243/275) where there was preoperative agreement between both. There were no malignant lesions. An average of 80 clinically apparent epidermoid cysts were excised and sent for histology each year at a cost of £4800 per annum.ConclusionThere was close agreement between clinical and final histological diagnosis of epidermoid cyst. Where a characteristic, odorous, toothpaste-like material is present on transection intra-operatively, the diagnosis is confirmed and the lesion can be discarded. We argue that significant cost savings can be achieved by adopting this approach.