Metastatic Squamous Cell Carcinoma of the Pleura: A Rare Complication of Hidradenitis Suppurativa

BACKGROUND Squamous cell carcinoma (SCC), also known as Marjolin ulcer, is a rare complication of hidradenitis suppurativa (HS). Metastatic SCC from HS typically involves the axial skeleton or abdominopelvic viscera. Metastatic disease to the lungs is a rare phenomenon with only three reported cases of lung parenchyma. We present a biopsy proven case of metastatic SCC to the pleura from gluteal HS. CASE REPORT A 46-year-old male with a history of recently diagnosed Marjolin ulcer secondary to gluteal HS was transferred to our intensive care unit for acute hypoxemic respiratory failure secondary to recurrent pleural effusion. On examination, patient was febrile (38.3 °C), normotensive (blood pressure 98/65 mm Hg), tachycardic (116 beats/minute) and tachypneic (40 breaths/minute) with oxygen saturation of 93% on room air. He was in moderate distress requiring endotracheal intubation and mechanical ventilation. Chest examination revealed decreased breath sounds bilaterally and skin examination was significant for 18 cm wide sacral lesion. CT thorax showed bilateral pleural effusions, pleural thickening, and scattered nodular densities within both lungs concerning for metastatic disease. Thoracentesis showed lymphocyte predominant exudate with negative cytology for malignant cells. A video-assisted thoracoscopic surgery (VATS) illustrated thickened pleural rind with histopathology and positive p40 stain consistent with invasive well-to-moderately differentiated keratinizing SCC.  CONCLUSIONS SCC arising from HS is rare and metastatic disease to the pleura has not been reported previously. Strong clinical suspicion for malignancy is warranted in patients with advanced HS and evolving pulmonary symptoms despite negative cytology.