Pathology of the Head and Neck

Larynx and Hypopharynx Chapter 7 225Histologically, the tumour consists of sheets of plasmacells that vary in differentiation from well- to poorlydifferentiated. They may contain Russell bodies orgrape-like inclusions of retained immunoglobulin (Mottcells), which are also found in reactive plasma cells anddo not help in establishing the diagnosis of plasmacytoma[142].Well-differentiated plasmacytoma cannot be distinguishedmorphologically from reactive (polyclonal) proliferationof plasma cells. Therefore, the monoclonalityof plasma cells must be proven, which is best achieved bydemonstrating the cytoplasmic immunoglobulin heavyand/or light chain restriction. Besides immunohistochemistry,non-isotopic paraffin section in situ hybridisationis useful in the assessment of clonality for kappaor lambda light chain mRNA [389].Poorly differentiated plasmacytoma must be differentiatedfrom other lymphoid neoplasms and from othermalignant tumours, such as malignant melanoma andcarcinoma. This is achieved by appropriate immunohistochemicalanalysis; plasmacytoma, in contrast to lymphoma,does not express CD45 and immature B- andT-cell markers [351]. It also does not express antigenscharacteristic of malignant melanoma (i.e. S-100 protein,HMB-45 and melan-A), carcinoma (cytokeratins)and neuroendocrine neoplasms (i.e. synaptophysin,chromogranin).Plasmacytoma is radiosensitive and complete eradicationby radiation and/or surgery is potentially curative[183, 269, 270, 303, 378]. The prognosis is favourable,although the development of a plasma cell myelomamay occur in 15% of patients with extraosseous plasmacytoma[142].7.7.6.3 Primary Mucosal MelanomaICD-O:8720/3Primary malignant melanoma (MM) of the larynx is extremelyrare; less than 60 cases have been described inthe literature. They represent 3.6 to 7.4% of all mucosalmelanomas of the head and neck [6, 185, 212, 379].Primary laryngeal MM is more common in men,mostly in the 6th and 7th decades. It occurs primarilyin the supraglottic region and less often in the glottic region,but it has not yet been described in the subglottis.The symptoms vary according to the site of involvementand generally occur over a short period of time [379].Macroscopically, it may present as a polypoid, exophytic,nodular, sessile, or pedunculated lesion, with orwithout surface ulceration, varying in colour from blackor brown, to tan-grey or white.Microscopically, primary laryngeal MM is indistinguishablefrom MM of the skin and other mucous membranes.It may be composed of epithelioid cells, spindlecells, or both. Nuclear and cellular pleomorphism, nuclearpseudoinclusions, mitoses and necroses are usuallyprominent.The diagnosis is based on histological examination,together with special stainings for melanin, such as Fontana-Masson,and immunohistochemistry.The differential diagnosis must always include thepossibility of a metastatic MM because in the larynx,metastatic MM is considerably more common than primaryMM [153]. Histologic features that favour the diagnosisof primary MM are junctional activity and/oran in situ component. However, as normal melanocytesare also normally present in the subepithelial compartment,junctional changes are not required for the diagnosisof primary MM [379].Apart from metastatic MM, the differential diagnosisincludes carcinoma (especially spindle cell carcinoma),sarcoma and lymphoma. Positive staining for wellknownMM markers, such as S-100 protein, HMB-45,melan-A and vimentin, and negative staining for CD45,B- and T-cell markers, as well as markers of epithelialdifferentiation (cytokeratins, epithelial membrane antigen)is diagnostic for MM.The treatment of choice is complete surgical excision.The prognosis of primary laryngeal MM is poor, similarto primary mucosal malignant melanoma in general,with an average survival of less than 3.5 years [260,379].7.7.6.4 Metastases to the LarynxMetastases to the larynx from distant primary tumoursare uncommon, accounting for less than 0.5%of all laryngeal neoplasms. Metastases to the hypopharynxand trachea are even less common. The mostcommon source is malignant melanoma (Fig. 7.15),followed by renal cell carcinoma. Other tumours withproven laryngeal metastases include cancer of thebreast, lung, prostate, colon, stomach and ovary [24,74, 105, 154, 267, 296]. The rare occurrence of metastasesto the larynx seems to be related to the terminallocation of this organ in the lymphatic and vascularcirculation.Laryngeal metastases are most commonly located inthe supraglottic and subglottic regions, presumably dueto their rich vascular supply [24, 133]. They can be dividedinto those located in the soft tissue (metastasesfrom melanoma and renal cell carcinoma) and those locatedprimarily in the marrow spaces of the ossified laryngealcartilage (metastases from breast, prostate, andlung cancer).The signs and symptoms of metastatic laryngeal tumoursdo not differ from those of other laryngeal tumoursand vary according to the site of involvement.Haemoptysis may be present, especially in highly vascularisedmetastatic renal cell carcinoma.