Gluteal Region Lymphoma presenting as Neurolymphomatosis

DISCUSSION

Malignancy of lymphocytes or lymphoblasts results in lymphoma which accounts for approximately 4% of all cancers.³ Lymphoma commonly presents as a nodal disease, however, presentation as an extranodal disease is not uncommon. Hodgkin lymphoma and low-grade Non Hodgkin Lymphoma (NHL) typically present as nodal disease, whereas high-grade NHL usually presents as extranodal disease. Extranodal disease can affect any part of the body. The most commonly involved site is the gastrointestinal tract followed by the lung, central nervous system, liver, spleen, and bone.⁴ Lymphoma of skeletal muscle is rare and accounts for up to 1.4% of all lymphomas.⁵ Literature search revealed a few cases of lymphoma originating in gluteal muscles.^2,6 However, we did not come across any case of gluteal muscle lymphoma infiltrating and extending along the lumbosacral nerve roots and presenting as an intradural mass. The peripheral nerve infiltration by lymphoma cells has been termed neurolymphomatosis (NL).

Neurolymphomatosis (NL) is an infrequent presentation of B-cell NHL. It is characterized by the direct infiltration of cranial nerves, plexus, nerve roots, or peripheral nerves with lymphoma cells. The patients have varied presentations depending on the nerves affected. Patients may present with painful or painless polyneuropathy, radiculopathy, or mononeuropathy depending on the extent or number of nerves involved. In this case, the patient initially presented with pain and swelling in the right gluteal region which progressed to weakness and debilitating pain along the back of thighs incapacitating the patient and making him bedbound. MRI is the initial investigation modality that can depict the involvement of the nerves. MRI was done in our case which revealed an enhancing soft tissue mass that was tracking along the nerves and through the L4-5 and L5-S1 neural foramen into the intradural compartment (Fig. 2). There was complete obliteration of dural space with myelography cut off upto D12 level (Fig. 3). In view of these findings a differential diagnosis of MPNST or myxopapillary ependymoma with extraspinal extension was given. Rationale for giving this differential was the perineural spread of a tumor. However, both these diagnoses were proved to be wrong on HPE.

The limited literature available describes three appearances of NL on MRI—(1) infiltrative mass displacing neural fascicles, (2) diffuse thickening of nerve and enhancement, and (3) thickening of individual nerve fascicles. None of the cases reported in the literature presented with large skeletal muscle mass infiltrating the peripheral nerve and extending into the spinal canal. MRI is the imaging modality of choice for evaluating nerves. It can demonstrate the focal or diffuse thickening of nerves or show enhancement of affected nerves on postcontrast imaging. The international primary central nervous system lymphoma collaborative group has stated that fluorodeoxyglucose-positron emission tomography (FDG-PET)/computed tomography (CT) might be more sensitive than MRI in the diagnosis of NL as they will show increased uptake in the affected nerves. In our case, FDG-PET/CT was not done as the gluteal lesion was accessible to trucut biopsy and the diagnosis of diffuse B-cell lymphoma was established on HPE.

Primary involvement of skeletal muscle in lymphoma is very rare, however skeletal muscle lymphoma presenting neurologically as NL has not been reported in the literature. It is important to keep lymphoma as a differential diagnosis if a mass is seen involving both intraspinal and extraspinal compartments.