Basal cell carcinomas (BCCs) are the most common keratinocyte cancers, which in rare circumstances can metastasise. Through haematogenous and lymphatic pathways, the most common sites of metastasis are the lymph nodes, lungs and bones. Due to the rarity of metastatic BCC (mBCC), diagnosis and surveillance can be challenging.
We describe a 64-year-old male with mBCC who presented with a subdermal neck metastasis, not identified on routine PET/CT. He was under surveillance for mBCC following an initial diagnosis of a back primary thirteen years ago. He has previously undergone surgical excision and adjuvant radiotherapy of multiple recurrences of his mBCC, as well as treatment with systemic therapies including Vismodegib and a Pembrolizumab-Interleukin-2 combined therapy. Trials of these systemic therapies were unfortunately ceased due to development of resistance and severe immune related side-effects, respectively. The patient’s most recent PET showed evidence of ongoing right axillary metastatic disease. Upon review for discussion of a right axillary lymphadenectomy, the patient was noted to have a subdermal mass deep to a previous right neck dissection scar which was not FDG-avid on the recent PET. However, an ultrasound guided core biopsy confirmed that this was in fact metastatic disease.
In this report, we discuss the importance of combining modern imaging modalities with a thorough clinical examination when completing surveillance for mBCC patients. Radiological investigations present varying capabilities when assessing for metastatic disease. PET-CT is superior in identifying larger tumours but are less reliable in identifying infiltrative, morpheaform and micronodular forms of BCC. MRI is reliable for assessing perineural invasion when used with contrast, however are costly and difficult to access.
Whilst imaging modalities continue to become more advanced and accessible, it is essential that thorough clinical examinations are prioritised when completing surveillance for mBCC patients to ensure potentially metastatic lesions are not missed.