Spontaneous regression of squamous cell carcinoma is a very rare event. We report a case of primary squamous cell carcinoma in the lacrimal sac which showed spontaneous regression without any treatment.

A 69-year-old woman presented with epiphora and ocular discharge from the right eye. Under the diagnosis of nasolacrimal duct obstruction, we performed dacryocystorhinostomy. Two years after the surgery, the patient presented again with severe epiphora and ocular pain accompanied by proptosis and adduction limitation in the right eye. Computed tomography demonstrated a mass occupying the right lacrimal sac and incisional biopsy showed poorly differentiated invasive squamous cell carcinoma. Additional treatment was recommended, but the patient denied any treatments. At 6 months after the biopsy, the medial orbital wall was partially destructed. On positron emission tomography/computed tomography, metastasis was suspected in the cervical, para-aortic, sub-carinal, and peri-esophageal lymph nodes. However, at 15 months after the biopsy, the orbital tumor had almost disappeared. On positron emission tomography/computed tomography, fluorodeoxyglucose uptake was reduced in all areas including the cervical and mediastinal lymph nodes.

This case exhibited a generally natural course of a malignant tumor, including medial orbital wall destruction and lymph node metastasis. However, the course then improved naturally without any treatment. The reason for the spontaneous regression of squamous cell carcinoma is still unclear but might be due to complex effects of one or several factors.