Extranodal lymphoma of the head and neck comprises a heterogeneous group of tumours with different histological types, modes of presentation and prognosis. Lymphomatous involvement of skeletal muscles and particularly muscles of mastication and facial expression is extremely rare, but primary muscle lymphoma should be considered in the differential diagnosis of muscle masses. This article highlights clinical, radiological and histopathological findings of primary extranodal non-Hodgkin’s lymphoma involving masseter and buccinator muscles in an immunocompetent patient.
Lymphomas constitute a broad range of lymphoproliferative disorders. They comprise 10% of all malignant tumours and 5% of head and neck cancers and are traditionally divided into Hodgkin’s and non-Hodgkin’s types . Both forms typically present with painless lymphadenopathy and frequently present to the head and neck surgeon. Non-Hodgkin’s lymphoma (NHL) differs from Hodgkin’s lymphoma in that it commonly demonstrates noncontiguous nodal spread, often found with extranodal involvement, and frequently disseminated at the time of diagnosis. Approximately 11–33% of cases of extranodal lymphomas involve the head and neck region . Most extranodal lymphomas of the head and neck are NHL (25–30%). The most common site being Waldeyer’s ring, although other sites, including the floor of mouth, salivary glands, buccal mucosa, paranasal sinuses, and bone, have also been reported .
Primary involvement of the skeletal muscles is uncommon. Muscle involvement in lymphoma usually occurs with widespread or recurrent disease. It usually affects the extremities such as the gluteal and pelvic areas. Only five cases of NHL arising in the muscles of mastication and two cases involving the muscles of facial expression have been reported.
The authors present the clinical, radiological and histopathological findings of a case of primary extranodal NHL infiltrating into right masseter and buccinator muscles in an immunocompetent patient.
A 55-year-old male patient presented with a painless swelling on the right cheek region of 2 years’ duration. The swelling was sudden in onset with gradual increase in size and was not associated with any discharge and neurological symptoms. There was no relevant medical history noted. He gave a history of smoking, 5–6 beedis per day, for 30 years.
On clinical examination a 5 cm × 6 cm dumb-bell shaped swelling was noted on the right side of face extending both below and above the zygomatic arch. Superiorly the swelling extended from the anterior temporal region, inferiorly up to the lower border of the mandible, laterally from the anterior border of the ramus of mandible and medially up to the commissure of the mouth ( Fig. 1 ). Intraoral examination revealed a well defined swelling of the right buccal mucosa spanning from the commissure to the pterygomandibular raphae obliterating the upper vestibule. The overlying mucosa was normal. There were no palpable nodes.
A provisional diagnosis of benign soft tissue tumour was made with lipoma, fibroma, rhabdomyoma, minor salivary gland tumour, benign neurogenic tumour was considered as differential diagnosis.
Blood profile, serological tests, liver function test, chest radiograph, abdominal scan and bone marrow biopsy were all negative. The orthopantomogram was normal. A soft tissue radiograph of the right buccal mucosa showed ill-defined hazy specks of radiopacity. Fine needle aspiration cytology of the lesion revealed lymphocytes and plasma cells suggestive of lymphadenopathy.
Ultrasound examination of the right cheek revealed a large hypoechoic lesion with muscle like texture in continuity with the massseter. On colour Doppler, the lesion showed very minimal vascularity. A plain CT scan of the face showed a 3 cm × 3.8 cm × 4.7 cm well defined lesion with homogeneous soft tissue density and mildly lobulated margins in the right buccal space. The lesion was superficial to the buccinator muscle with loss of fat plane with this muscle. Posteriorly it abutted the anterior border of the masseter and ramus of the mandible with loss of fat plane.
Superiorly the lesion extended into the masticatory space up to the level of condylar neck. There was homogeneous enhancement of the lesion following intravenous contrast with no evidence of calcification, cystic changes or necrotic areas within the lesion ( Fig. 2 ). Magnetic resonance imaging (MRI) was performed and T1-weighted spin-echo (SE), T2-weighted fast spin-echo (FSE), and T2-weighted fat-suppressed images were obtained. A well defined altered signal intensity soft tissue mass was seen in the right buccal and masticatory space. The lesion was sandwiched between the posterolateral wall of the maxilla and ramus of the mandible and masseter muscle. The lesion was isointense to muscles on T1-weighted images, heterogeneously hyperintense on T2-weighted FSE and hyperintense on T2-weighted fat suppression sequences ( Fig. 3 ).