A rare case of inter-compartmental giant lipoma of right distal forearm dorsal compartment invading anterior compartment via breaching inter-osseous membrane.

Lipomas are benign soft masses of adipose cells, which are often encapsulated by a thin layer of fibrous tissue and are most commonly present in head, neck, shoulders, and backs of patients. The tumors typically lie in the subcutaneous tissues of patients. Inter-muscular lipomas however, are rare and always occur deep within muscle compartments comprising 0.3% of all lipomas. Deep lipomas are most commonly found in the lower limbs followed by trunk, shoulders and arm. We present a rare case of deep dorsal inter-compartmental inter-muscular giant lipoma (>8cm) of right distal forearm leading to the formation of ganglion in the tendon sheath of Flexor Carpi Radialis (FCR) of anterior compartment as a result of breaching of inter-osseous membrane. MRI findings were indicative of a benign inter-compartmental lipoma of dorsal aspect of right distal forearm that erodes through distal inter-osseous membrane to enter the distal volar aspect of the wrist and therefore we did an excision biopsy and histo-pathological examination of the swelling reported an encapsulated tumour composed of mature adipose cells, which were uniformly arranged without high variations in size, consistent with benign lipoma. To the best of our knowledge, after an extensive search of literature we present this rare case of deep dorsal inter-muscular lipoma of forearm crossing over to the volar compartment resulting in ganglion formation in FCR tendon sheath.