Parathyroid Hormone Related Protein Mediated Hypercalcaemia Due to Metastatic Squamous Cell Carcinoma Originating from Pilonidal Disease: A Case Report.

A 56-year-old male presented with a longstanding, gradually enlarging, painful, skin lesion over the natal cleft. This was initially thought to be a pilonidal abscess but, following multiple surgeries, he was diagnosed with Stage IVb squamous cell carcinoma of the natal cleft skin with bilateral inguinal lymph node metastases and subcutaneous metastatic deposits. Complete surgical cure was not possible. He underwent radiotherapy, cisplatin chemotherapy and cemiplimab immunotherapy to control his disease. His course was complicated by severe humoral hypercalcaemia of malignancy (HHM) resistant to medical therapy. His disease progressed, and he developed widespread metastases. He was thus transferred to palliative care with pain control being the major priority. He died within a year of diagnosis.