Primary Cutaneous Adenoid Cystic Carcinoma with Pulmonary Metastases, Five Years after the Initial Diagnosis: Case Report and Literature Review

الملخص

Adenoid cystic carcinoma is a malignant neoplasm mostly originating from the salivary glands but it has also been reported to arise in several other sites including the skin. Primary cutaneous adenoid cystic carcinoma (PCACC) was first described by Raul Boggio in 1975. Case reports then followed describing similar tumors with some reporting a metastatic tumor at presentation, and others reporting late metastases occurring as late as 21 years after initial diagnosis. We report a case of a 65 year old male patient who presented with pulmonary metastases from a scalp adenoid cystic carcinoma diagnosed 5 years previously. A brief literature review is included which focuses on discussion of the behavior and prognosis of these lesions and their potential to metastasize. Metastasis of this tumor is more ominous than originally suggested; as the metastatic rate is close to 10% and can appear after a long time span which mandates a long term follow up. We also challenge the reliance on thyroid transcription factor (TTF1) immuno-histochemical stain to differentiate primary pulmonary from metastatic adenoid cystic carcinoma. Our case and the experience of other researchers reveal that TTF1 can be positive in pulmonary metastases but negative in the primary lesion.