Before becoming invasive, lung epithelium may undergo morphological changes that include hyperplasia, metaplasia, dysplasia, and carcinoma in situ.

Rare neoplasms at this site that can give rise to discharge include Paget's disease (which is possibly a type of adenocarcinoma) and verrucous carcinoma.

The malignant lesions include adenocarcinoma, undifferentiatedcarcinoma, acinic cell carcinomas, and mucoepidermoid carcinoma.

Other types of common eyelid cancers include squamous carcinoma, sebaceous carcinoma and malignant melanoma.

The histologic differential diagnosis includes adenoid cystic carcinoma and pleomorphic adenoma.

The microscopic differential diagnosis includes endometrial carcinoma and endocervical adenocarcinoma.

Other causes include chronic renal failure, hypothyroidism, bronchogenic carcinoma and sarcoidosis.

The differential diagnosis includes carcinoma ex-pleomorphic adenoma and undifferentiated carcinoma.

The Malignant tumors include ceruminous adenocarcinoma, adenoid cystic carcinoma, and mucoepidermoid carcinoma.

Common misdiagnosis include carcinoma, appendicitis, amebiasis and tuberculosis.