Squamous Cell Carcinoma of the Lung in McCune-Albright Syndrome.

McCune Albright Syndrome (MAS) is caused by a mutation in the GNAS gene that results in multiple endocrinopathies such as Cushing syndrome, acromegaly, hyperthyroidism, and precocious puberty. Despite the presence of pleiotropy coupled with a GNAS gene mutation, malignancy is a rare occurrence in MAS. There is minimal literature showcasing squamous cell carcinoma (SCC) of the lung in patients with MAS. Here, we report a case of altered mental status and hypercalcemia in a 72-year-old female with a past medical history of fibrous dysplasia. On examination there was an expansive lesion of the left hemipelvis that had been present since birth; it was determined to be a characteristic of polyostotic fibrous dysplasia seen in MAS. Lab results revealed an elevated parathyroid hormone-related protein (PTHrP) and a chest X-ray (CXR) displayed masses in the right upper lobe. Computed tomography (CT)-guided lung biopsy confirmed the masses to be SCC of the lung. This case primarily highlights the importance of investigating other malignancies found in patients with MAS. Current literature shows that the GNAS mutation is an oncogenic driver in many tumor types such as pancreatic adenocarcinoma, adrenocortical carcinoma, and thyroid carcinoma; however, current data are limited on the role of GNAS mutations in SCC of the lung. In addition, it is important to investigate malignant causes of hypercalcemia in patients with MAS. The clinical features and treatments of MAS can lead to hypercalcemia and hypophosphatemia and thus mask a malignancy. Clinicians must be wary of a masked malignancy, as it could delay treatment and negatively impact overall outcomes for patients with MAS.