|
Discussion |
A.A. MAHESHWAR*, A. G. DOUGLAS-JONES # and P.J.CUDDIHY *
*Departments of Ear, Nose and Throat and #Pathology , University Hospital of Wales, Cardiff, U.K.
A rapidly enlarging lump in the neck of an adolescent, is a cause for concern. Amongst the various clinical differential diagnoses, including lymphoma and other malignant lesions, focal myositis is an unusual cause. To date, only two such cases affecting the sternomastoid have been reported worldwide. We report a further similar case.
Keywords: myositis, neck mass
J.R.Coll.Surg.Edinb., 45,October 2000, 339-341
A 16-year-old girl presented to the clinic with a 3-week history of a large lump in her neck on the left side. She had a bout of tonsillitis 10 days prior to developing the lump, which had been treated with appropriate antibiotics. She had had numerous attacks of tonsillitis in the past, although this episode was relatively mild. The neck swelling was painful and had varied in size from time to time. There was no history of trauma to that region. On examination, there was a firm mass along the left sternomastoid extending from the jugulodigastric region to the root of the neck. It measured about 6 by 4 cms. Her throat was healthy and she had no other systemic abnormality. A recent blood test had ruled out glandular fever and her white cell count was slightly raised with a neutrophilia. Since there was a distinct possibility of this being a lymphoma, it was decided to biopsy it and examine the post nasal space under anaesthesia. At the operation, a hard mass was found arising in and infiltrating the left sternomastoid muscle. Multiple biopsies were taken which confirmed focal myositis of the sternomastoid. When reviewed 4 weeks later, the lesion had all but disappeared and the wound had healed well.
The biopsied tissue was fixed in formalin and routinely processed. Sections stained with haematoxylin and eosin showed adipose tissue, connective tissue and skeletal muscle. There were foci of skeletal muscle degeneration and necrosis with focal infiltration of neutrophil leukocytes. In other areas there was degeneration of skeletal muscle fibres with a minimal inflammatory reaction. In some other areas, there appeared to be maturing granulation tissue infiltrated by lymphocytes. Individual muscle fibres appeared to be undergoing degeneration, associated with a lymphocyte infiltrate. No organisms could be demonstrated on staining for bacteria or mycobacteria and no vasculitis could be identified. There was no evidence of invasive tumour and the lymphocytic infiltrate was not indicative of a lymphoma. Immunocytochemistry was performed on paraffin-embedded tissues for CD45 leucocyte common antigen, CD20, CD45 RO, CD3, CD4, CD8 and kappa and lambda light chains. The B cells in the infiltrate were aggregated together around neurovascular bundles whereas the T cells were distributed diffusely between muscle fibres. CD8+ T cells were more numerous than CD4+ cells, which were scanty. There were approximately equal numbers of B cells containing kappa and lambda light chains. The histological diagnosis was that of focal myositis.
Figure 1: Skeletal muscle showing a band of cellular fibroblastic tissue and a lymphocytic infiltrate between muscle fibres (Haematoxylin and Eosin x 100)
Figure 2: Focal degeneration of muscle fibres with a lymphocytic infiltrate composed mainly of T lymphocytes on immuno-cytochemistry (Haematoxylin and Eosin x 400)
Focal myositis of the sternomastoid is a rare condition. It has been reported only twice before in children. The largest series to date was reported in 1977, by Heffner et al1 involving 16 cases, all of which affected the limbs. It was also the first known description of this entity. This focal inflammatory process can affect various muscles, most commonly those of the limbs. There are reports of focal myositis involving the muscles of the head and neck, including the temporalis muscle2 and the muscles of the tongue2,3. Shapiro et al.4 and Isaacson et al.5 have reported focal myositis in the sterno-mastoid in children.
Apart from its rarity, the lesion is an interesting clinical and pathological entity. The clinical presentation and appearance is that of a malignant neoplasm of the muscle, but it has a completely benign clinical course. It presents as a rapidly enlarging intra muscular mass with no previous history of trauma. Although a computerised tomographic scan was not performed in this case, the evidence from published data reveals a diffuse swelling of the involved muscle with oedema around it. Aspiration cytology is likely to yield lymphocytes only, which raises the suspicion of a malignant lymphoma. The diagnosis is made on open biopsy. At surgery, the mass is found to be within the muscle, appears pale and is rubbery in consistency. It is poorly demarcated from the surrounding muscle and not attached to the skin. The biopsy reveals an inflammatory infiltrate with muscle fibre degeneration and regeneration but no evidence of malignancy.
Clinically and histologically the differential diagnosis includes sarcoma and lymphoma and pseudotumour such as, myositis ossificans and proliferative myositis. In patients with polymyositis, discrete nodules can occur in individual muscles, along with systemic symptoms including fever, malaise, dysphagia and arthralgia. The erythrocyte sedimentation rate and creatine phosphokinase levels are raised. The muscle fibre hypertrophy, fibre splitting, interstitial fibrosis and basophilic giant cell infiltration that are seen in polymyositis, are absent in focal myositis. In nodular fasciitis, the lesion primarily involves the subcutaneous tissues or fascia of the upper extremity. Histologically, there are hypercellular, pseudosarcomatous areas composed of increased numbers of capillaries, immature fibroblasts and multi-nucleated giant cells. These features are not seen in focal myositis. In addition, the connective tissue proliferation in focal myositis is minimal.1 The histology in myositis ossificans includes mineralised deposits and osseous or cartilage formation, which are absent in focal myositis. Eosinophilic myositis, which may exist with hypereosinophilic syndrome, giant cell or granulomatous myositis, in which granulomata are seen in the biopsy and acute focal suppurative myositis, in which micro-organisms and polymorphs are detected, should also be considered in the differential diagnosis.6
The aetiology of focal myositis is unknown. Various theories, including viral infection,7 denervating processes8 and ischaemic necrosis of muscle, have been suggested, but not established. Although trauma was originally proposed as an initiating factor, various subsequent reports have not supported this. In most reports, as in our case, there is no history of trauma to the affected site. In our case, lymphocyte phenotypic markers demonstrated a mixed B and T cell population with no evidence of kappa or lambda immunoglobulin light chain restriction. These findings exclude the possibility of involvement by lymphoma and indicate a reactive rather than a neoplastic lymphocytic population. The immunocytochemical analysis of the lymphoid infiltrate showed the presence of perivascular B cells and a diffuse T cell infiltrate with few CD4+ T cells. These results are in agreement with other published immunocytochemical analysis of the lymphocyte population in focal myositis.7 Although infection as an aetiology has also been postulated, electron microscopy and histopathology have failed to reveal either viral particles or evidence of bacterial infection.
Despite its rarity there have been a few reports of this unusual lesion in the literature. Our case differs from the few published cases in a number of aspects. Heffner's report8 states the presence of denervation as an important factor in his group of four cases. The electron microscopic examination of intramuscular nerves had disclosed scattered swollen axons that were actively undergoing demyelination. He emphasised that these changes may be striking in focal myositis. He also suggests that denervation may be the cause or the effect of focal myositis. In our case there was no evidence of axonal demyelination. Naughton et al described two cases of focal myositis.6 Both of these were characterised by repeated admissions with relapse occurring in previously unaffected muscle groups. The patient reported in our case had spontaneous resolution with no recurrence after nearly a year. In the case presented by Isaacson5 there was both clinical and histological evidence of a more intense inflammatory process; the patient appeared ill with progressive systemic symptoms and signs. Histology also showed an extensive inflammatory infiltrate. Our case differs markedly from the latter. The patient neither appeared ill nor did she have systemic symptoms and signs. The focal myositis involving the sternomastoid muscle regressed after one year in the case reported by Ho et al9 and in 6 months in the case reported by Shapiro et al.4 In the young lady reported here, there was complete spontaneous resolution within 4 weeks.
Focal myositis is a rare condition, only two such cases involving the sternomastoid muscle in the paediatric age group have been reported hitherto. The disease is self-limiting, resolves spontaneously and has a good prognosis. We have presented only the third such case, which differs from other reports in a number of important aspects. Although a clinical suspicion of a malignant neoplasm should always be considered, rarely one may be surprised with a diagnosis of focal myositis on biopsy.
Copyright date: 16th August 1999
Correspondence: Mr. A. A. Maheshwar, Department of E.N.T,
Princess of Wales Hospital, Coity Road, Bridgend CF31 1RQ
E-Mail: Maheshwar@Compuserve.com
©2000 The Royal College of Surgeons of Edinburgh, J.R.Coll.Surg.Edinb.