Primary salivary gland-type tumors of the lung

Primary pulmonary neoplasms that bear similar histopathologic features to those seen in salivary glands are rare. Although their presence has been well documented in the literature, it has been primarily in the form of single case reports. Consequently, it has been difficult until recently to determine their prevalence, clinical behavior, treatment, and spectrum of histopathologic features. Moreover, because of the rarity with which these tumors occur, one needs to be familiar with their diverse histopathologic features to comfortably arrive at the correct diagnosis. Because of their close histological similarities to their salivary gland counterparts, careful clinical evaluation is necessary to establish the primary nature of these tumors in the lung and to rule out the possibility of a metastasis. Another feature that may generate difficulties in interpretation is that some of these tumors may share certain histopathologic and some immunohistochemical features with each other. This may pose a serious problem, particularly when dealing with small biopsy samples. Therefore, the use of special studies such as electron microscopy and routine histochemistry may be beneficial and must be used in addition to conventional microscopy and immunohistochemistry to corroborate the diagnosis. In essence, the diagnosis of these tumors requires a combined approach that must include a detailed clinical history, a reasonably sized sample for histopathologic evaluation, histochemical and immunohistochemical studies, and an ultrastructural examination.