Detection by (18)F-FDG PET of unsuspected extensive bone marrow metastases in a case of basosquamous carcinoma of the cheek.

Basosquamous carcinoma (BSC) is a rare type of malignancy with features of both basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) with a potential for aggressive behaviour infiltration and destruction. First reported by MacCormac in 1910 in a series of rodent ulcers, this entity does have an increased risk of recurrence and metastases as well, which distinguish it from other forms of basal cell carcinoma. The overall incidence of basosquamous carcinoma ranges from 1.2% to 2.7%. An unusual case of basosquamous carcinoma (BSC) is presented where 18- fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) scan diagnosed unsuspected extensive metastatic disease in the bone marrow, which was further proven histopathologically. The patient was a 32 years old man with history of recently diagnosed basosquamous carcinoma of left cheek involving left lower eyelid and left eyeball. Contrast enhanced computed tomography(ceCT) of the head and neck demonstrated involvement of the left cheek skin by the malignancy along with erosion of zygomatic bone and phthisis bulbi of the left eye. The serum alkaline phosphatase was elevated (255units, normal range 50-150units). The patient was referred for (18)F-FDG PET, for disease status evaluation. The scan showed intense tracer uptake in the left zygomatic region, the site of known primary disease. Intense tracer uptake was noted in the multiple lesions of bone marrow of axial as well as appendicular skeleton. The scan appearance was highly suggestive of metastatic bone marrow involvement. A bone marrow biopsy was performed to confirm the scan findings. Guided by the (18)F-FDG PET scan findings, bone marrow biopsy was performed and metastatic basosquamous carcinoma was diagnosed. We believe this is the first reported case of basosquamous carcinoma where extensive metastatic bone marrow disease was diagnosed with the aid of (18)F-FDG PET. At first diagnosis, an advanced stage of BSC is often present. Due to its metastatic potential, extensive primary surgical resection of BSC, possibly completed by radiation or photodynamic adjuvant treatment is recommended. Given the aggressive nature of basosquamous carcinoma, whole body (18)F-FDG PET is very useful in diagnosing metastatic BSC. In conclusion, this is the first reported case of the use of (18)F-FDG PET study for diagnosing metastatic bone marrow disease in a patient with basosquamous carcinoma.