Pulmonary Metastases of Pseudo-Adenomatous Basal-Cell Carcinoma (Mucous and Salivary Gland Tumor)

Mucous and salivary gland neoplasms comprise a diverse group in respect to sites of origin, clinical evolution, histologic pattern, and degree of malignancy. In the literature, one of these tumors bears a multiplicity of names: basal-cell carcinoma with cylindromatous transformation, basaloma, cylindroma, adenoid cystic epithelioma, adenocarcinoma, pseudo-adenomatous basal-cell carcinoma, and others. At the University Hospital (University of Michigan) this tumor, whose most prominent feature consists of tubular or cord structures made up of cuboidal epithelial cells identical with the cells of basal-cell carcinoma, is designated as pseudoadenomatous basal-cell carcinoma. In Ahlbom's monograph, (1) most of the neoplasms of this histologic type are classed as semi-malignant or malignant. Local invasion, regional lymph-node metastases, and remote metastases (chiefly pulmonary) have been reported. Both the primary tumor and the metastases have been described by Ahlbom as having “a sedate course” clinically. This observation regarding the metastases appears, however, to be based on the evolution of those in the regional lymph nodes. Little information is available on the clinical course of pulmonary metastases except for a single case reported by one of the present authors in 1942 (2). Since then, additional patients with pulmonary metastases have been seen and followed. These cases present an essentially uniform clinical pattern which merits emphasis from the point of view of the natural history of the neoplasm. Lack of knowledge in this respect may lead to error in the management of the disease. Review of the records at the University Hospital, from 1930 to date, disclosed 25 cases of pseudo-adenomatous basal-cell carcinoma. The sites of origin were as follows: palate 3, parotid 3, lacrimal gland 2, submaxillary salivary gland 1, paranasal sinuses 6, nasopharynx 3, oral part of the tongue 4, pharyngeal portion of the tongue 1, elsewhere in the oral cavity 2. Pulmonary metastases were discovered by roentgenographic examination in 5 (20 per cent) of the patients. As a result of the confusion which has existed in the classification of this tumor, particularly in the earlier years, cases may have been lost. Indeed, 22 of the 25 cases have been diagnosed since 1936. Because of this, one may argue that 20 per cent is too high an incidence figure. On the other hand, 7 patients did not have chest roentgenograms, so that pulmonary metastases may have been overlooked (as will become apparent from the discussion to follow). Furthermore, in the remaining 13 with negative chest roentgenograms, the examinations covered a period of five years in one patient, two and three-quarter years in one, eleven months in another, six and two months, respectively, in 2 more. In 8 patients, only a single examination was done. In 6 of the 8, the interval between onset of the disease and roentgenography was two years or less.