A Large Palmar Atypical Lipomatous Tumor Extending Into the Carpal Tunnel and Guyon's Canal: Challenges in Nerve-Sparing Surgical Excision.

We report a complex case of a large atypical lipomatous tumor (ALT) extending into the carpal tunnel and Guyon's canal, highlighting the diagnostic considerations, anatomical challenges, and principles of safe surgical excision. A 67-year-old female presented with a progressively enlarging swelling involving the thenar, mid-palmar, distal palmar, and wrist regions. Examination revealed a large palmar mass without neurovascular deficit or muscle wasting. MRI demonstrated a 63 × 27 × 79 mm lipomatous lesion arising from the volar wrist and extending into the carpal tunnel and Guyon's canal, with internal septations and mild heterogeneity, raising suspicion for an ALT versus low-grade liposarcoma. Following the Sarcoma Multidisciplinary Team (MDT) discussion, surgical excision was planned under the plastic surgery department. A volar approach was used. The lesion was predominantly superficial in the radial palm but extended deeply into Guyon's canal, where it was closely related to the ulnar neurovascular bundle and abutted the median nerve within the carpal tunnel, with the radial neurovascular bundle incorporated within the tumor pseudocapsule. Careful microsurgical dissection was required to separate the tumor from the common digital nerves while preserving both the median and ulnar nerve branches. En bloc excision was achieved with no residual tumour. Histology confirmed an ALT. The patient recovered well and was discharged the same day. This case highlights the complexity of large palmar lipomatous tumors extending into confined neuroanatomical spaces. Preoperative MRI and MDT planning were essential in guiding the operative strategy. The case emphasises meticulous dissection and nerve preservation while achieving complete en bloc oncological excision and maintaining hand function, making it a valuable learning case.