Sinonasal melanoma

Definition

Primary malignant melanoma of the nasal cavity, paranasal sinuses and nasopharynx.

Epidemiology

This is a rare tumour, although the most common mucosal site of malignant melanoma, with an incidence from 0.018 to 0.051 / 105 per annum1. They account for 4% of sinonasal tract neoplasms. There is a wide age range, but this is most often a tumour of the elderly. There is a suggestion of an association with occupational exposure to formalin (not pathology staff!)1,5.

Clinical features

Patients commonly present with epistaxis, a mass or obstructive symptoms, less often with difficult breathing, pain, polyps or a nasal discharge. Occasionally, there is melanorrhoea - a "coal flecked" or brown nasal discharge, suggesting the diagnosis.

Macroscopic appearances

The majority of the tumours are polypoidal and about half appear brown or black1.

Histopathology

A minority (41/1151) of tumours show either derivation from the surface epithelium or pagetoid involvement of the epithelium. The growth pattern may be solid, spindled, peritheliomatous or meningothelial. There may be focal storiform, psueodpapilary or alveolar patterns. The majority of cases (77/1151) show pigment within neoplastic cells. There may be evidence of regression in the form of fibrosis and granulation tissue-like vessels.

The tumour cells are most often small to medium size and undifferentiated, but may be epithelioid, spindled, plasmacytoid or rhabdoid. There may be tumour giant cells with eosinophilic cytoplasm.

There is commonly an inflammatory cell infiltrate, variably composed of lymphocytes and plasma cells. A few tumours (6/1151) contain metaplastic bone.

Immunohistochemistry the immunoreactivity is similar to that of cutaneous melanomas.

A panel of S-100, HMB-45 and tyrosinase identified all cases1.

Differential diagnosis

A combination of junctional activity and melanin is diagnostic of sinonasal melanoma.

• Metastasis from an integumentary site: only 1% of patients develop sinonasal metastases and it is very unlikely unless the patient has other metastases.

Pleomorphic melanoma:

• poorly differentiated carcinoma - negative for vimentin

• epithelioid angiosarcoma

• anaplastic large cell lymphoma

• rhabdomyosarcoma

Small cell melanoma: "small blue round cell tumours":

• olfactory neuroblastoma - negative for vimentin

• PNET / Ewing's sarcoma

• melanocytic neuroectodermal tumour of infancy

• pituitary adenoma

• small cell carcinoma

• lymphoma

• plasmacytoma

• mesenchymal chrondrosarcoma

Spindle cell melanoma:

• inflammatory scarring processes

• MPNST

• fibrosarcoma

• MFH

• leiomyosarcoma

• synovial sarcoma

Staging

A TNM staging has been suggested1:

T1: single anatomic site
T2: two or more anatomic sites
N1: any nodal metastasis
M1: distal metastasis
Stage I: T1, N0, M0
Stage II: T2, N0, M0
Stage III: any T, any N1 and/or M1

References

1Thompson, L. D., J. A. Wieneke, et al. (2003). “Sinonasal tract and nasopharyngeal melanomas: a clinicopathologic study of 115 cases with a proposed staging system.” Am J Surg Pathol 27(5): 594-611.

2Brandwein, M. S., A. Rothstein, et al. (1997). “Sinonasal melanoma. A clinicopathologic study of 25 cases and literature meta-analysis.” Arch Otolaryngol Head Neck Surg 123(3): 290-6.

3Franquemont, D. W. and S. E. Mills (1991). “Sinonasal malignant melanoma. A clinicopathologic and immunohistochemical study of 14 cases.” Am J Clin Pathol 96(6): 689-97.

4Henzen-Logmans, S. C., C. J. Meijer, et al. (1988). “Diagnostic application of panels of antibodies in mucosal melanomas of the head and neck.” Cancer 61(4): 702-11.

5Holmstrom, M. and V. J. Lund (1991). “Malignant melanomas of the nasal cavity after occupational exposure to formaldehyde.” Br J Ind Med 48(1): 9-11.

6Prasad, M. L., A. A. Jungbluth, et al. (2001). “Expression of melanocytic differentiation markers in malignant melanomas of the oral and sinonasal mucosa.” Am J Surg Pathol 25(6): 782-7.

7Regauer S. Anderhuber W. Richtig E. Schachenreiter J. Ott A. Beham A. Primary mucosal melanomas of the nasal cavity and paranasal sinuses. A clinicopathological analysis of 14 cases.APMIS 1998;106(3):403-10.

8Prasad S, Jones AS, Helliwell TR. Immunocytochemical labelling in the diagnosis of sinonasal malignant melanoma. Pathological Society January 2005, abstract 66.

This page last revised 27.12.2004.

©SMUHT/PW Bishop