Case 188 - Discussion

Uploaded: 2008-02-28, Updated: 2008-03-03

Mucoepidermoid Carcinoma of the Bronchus

The Key Features

  • Three components: mucus-secreting, squamous, and intermediate cells

CLINICAL FEATURES

  • WHO definition: a tumor with a combination of mucus-secreting, squamous, and intermediate cell types;

  • Usually arises in the salivary glands, including parotid, submandibular, and the minor salivary glands;

  • Mucoepidermoid carcinoma of the bronchus is rare, accounting for 0.1% to 0.2% of primary lung tumors; 10% of primary malignant pulmonary neoplasms in childhood;

  • Age: 3 to 78 years;  males = females;

  • Typically involve large airways, and the clinical symptoms and signs  include cough, hemoptysis, bronchitis, wheezing, fever, chest pain, and rarely, clubbing of the fingers.

  • Has similar features to its counterpart in the salivary glands but also some distinct characteristics of its own;

GROSS FINDINGS

  • Mainly involves the trachea and the main or lobar bronchi, but occasionally segmental bronchi or the peripheral lung;

  • Usually presents as an exophytic luminal mass;

  • The cut surface is gray-white-tan with a glistening mucoid texture and occasionally cystic degeneration.

MICROSCOPIC FINDINGS

  • The tumor is usually endobronchial and polypoid  that is closely associated with the adjacent submucosal glands;

  • Three components, mucus-secreting, squamous, and intermediate cells, in glandular, tubular, cystic, nested, or solid patterns;

    • Mucus-secreting cells: usually large with light blue-gray mucinous cytoplasm. Variants of mucus-secreting cells include columnar, goblet, cuboidal, clear, or occasionally oncocytic cells. Mucoid substance are intra or extra-cellular;

    • Squamous cells: admixed with the mucus-secreting cells and intermediate cells, or  form small nests with intercellular bridges but no keratin whorls or pearls;

    • Intermediate cells:  polygonal cells, no specific differentiation, with a centrally or eccentrically located bland nucleus and relatively abundant amphophilic or slightly eosinophilic cytoplasm. Usually located at the periphery of the glands or form nests.

  • The relative ratio of these components varies considerably and serves as one of the histologic criteria for grading this tumor;

  • Other unusual features: calcification and prominent lymphoid proliferation;

  • High-grade lesions: necrosis, nuclear pleomorphism, active mitosis, and intermediate or squamous cells in solid or nested patterns;

DIFFERENTIAL DIAGNOSES

  • Adenocarcinoma of the lung

  • Adenosquamous carcinoma

IMMUNOHISTOCHEMISTRY AND SPECIAL STAINS

  • Positive: CK7, CK5/6;

  • Negative: TTF-1, CK20;

CYTOGENETIC STUDIES

  • Several reciprocal chromosomal translocations frequently involving chromosome 11, including t(1;11)(p22;q13) with resultant over-expression of cyclin D1, t(11;19)(q14-21;p12), and t(11; 19)(q21;p13), which encodes a novel fusion product, MECT1-MAML2.

TREATMENT AND PROGNOSIS

  • Surgically treated by lobectomy, sleeve resection, local resection, segmental resection, or even endoscopic removal;

  • In 1 review report involving 45 patients with disease-free follow-up ranging from 8 months to 21 years, 1 patient had lymph node metastasis and died, 1 patient developed lymph node metastasis at 5 years of follow-up, and 1 patient had questionable lymph node metastasis.

REFERENCES

  • Archives of Pathology and Laboratory Medicine: Vol. 131, No. 9, pp. 14001404.