Pathology of the Head and Neck

Larynx and Hypopharynx Chapter 7 213ly, the histiocytes are strongly positive for S-100 proteinand Leu-M1. No nuclear and cytoplasmic atypiais observed.Differential diagnosis includes infectious diseases(rhinoscleroma), Wegener’s granulomatosis, NK/T lymphomaof the nasal type, eosinophilic granuloma, Hodgkin’slymphoma and fibroinflammatory disorders. Rhinoscleromais characterised by a proliferation of largemacrophages (Mikulicz cells) in which Klebsiella rhinoscleromatiscan be identified. In this disease the phenomenonof emperipolesis is not found. Histologically,in Wegener’s granulomatosis the S-100 positive histiocytesare lacking, while NK/T lymphoma of the nasaltype shows an infiltration of malignant lymphoidcells. Eosinophilic granuloma is histologically similarto Rosai-Dorfman disease, but differentiation is possiblewith the morphologic specificities of the Langerhanscells, characteristic of eosinophilic granuloma: their nucleishow lobulation, indentation or longitudinal grooving.Finally, fibroinflammatory lesions, such as aggressivefibromatosis, can be easily differentiated due to therelatively acellular appearance compared with the characteristiccellular infiltration in Rosai-Dorfman disease[381].Some rare laryngeal lesions may clinically and pathologicallymimic neoplastic growth and could be rangedin a category of pseudotumours: hamartoma [282, 314],warty dyskeratoma of the vocal cord [178], and Kimuradisease of the epiglottis [58].7.5.7 InflammatoryMyofibroblastic TumourICD-O:8825/1Inflammatory myofibroblastic tumour (IMT) is clinicopathologicallya well-defined fibroinflammatory proliferativelesion with unpredictable biological behaviour.Lung, gastrointestinal and genitourinary tract systemsare the commonest sites for IMT, although the lesionhas been reported throughout the body [382]. It rarelyaffects the head and neck region, and only a few welldocumented IMTs have been found in the larynx andpharynx [65, 96, 167, 188, 382].The aetiology of the lesion is unknown, but differentinfections with an exaggerated response to someunknown microorganism or post-traumatic eventshave been attributed as causal factors [9, 76, 167, 382].Most reported laryngeal IMTs are polypoid or pedunculatedlesions that occur in the true vocal cords or inthe subglottic area. Hoarseness, foreign body sensation,dyspnoea and stridor are presenting symptoms.Patients with laryngeal IMTs are mainly adult males[382].Histologically, IMT is composed of myofibroblasticspindle cells, admixed with a prominent infiltrateFig. 7.9. Inflammatory myofibroblastic tumour. Lesion is composedof uniform spindle cells, intermingled with inflammatorycellsof lymphocytes, plasma cells and neutrophils. The nucleiof the spindle cells are elongated, slightly polymorphous,containing one or more small nucleoli, the cytoplasmis palely eosinophilic (Fig. 7.9) . Occasional regularmitoses are seen. Inflammatory cells are unevenlydistributed within the lesion.Three basic histological patterns have been described:1. Myxoid/vascular pattern, resembling inflammatorygranulation tissue;2. Compact spindle cell pattern with fascicular and/orstoriform areas with various cellular density;3. Hypocellular pattern, densely collagenised and reminiscentof a fibrous scar [64].Immunohistochemistry confirms the myofibroblasticphenotype of the spindle cells, which are typically reactiveto vimentin, smooth muscle actin, and muscle-specificactin [64, 382]. Additionally, ALK1 and/or p80 werereported in a cytoplasmic pattern in 40% of cases of IMT[56]. Both markers are useful indicators of a 2p23 abnormality,suggesting the neoplastic nature of positive casesof IMT. However, it must be interpreted in the context ofhistologic and other clinicopathologic data if used as anadjunct to differential diagnosis [56].Radical excision of the lesions has been reported to becurative in more than 90% of extrapulmonary IMTs, includinghead and neck lesions [63]. Six out of seven patientswith laryngeal IMTs in Wenig’s series were free ofdisease over periods of 12 to 36 months after completeexcision. In one patient, laryngectomy was required afterrecurrence of the disease [382]. A metastatic potentialhas been exceptionally noted in patients with abdominaland mediastinal IMTs. However, a fatal outcomeof a patient with IMT of the paranasal sinuses has