The law of paired cases on the example of adenocystic cancer of salivary glands tissue with multicentric growth of different locations

Adenoid cystic cancer of the salivary glands is characterized by recurrent and/or metastatic course. Compared with other histological types of salivary gland cancer, it usually has a more latent clinical course with a low incidence of spread to regional lymph nodes. However, after removal of the primary tumor, local and distant relapses are quite common. In addition, the presence of prognostic factors such as metastases in the lymph nodes of the neck, low degree of tumor differentiation, perineural and lymphovascular invasion contributes to an increase in the frequency of distant metastasis with a poor prognosis.

Cases of atypical arrangement of salivary gland tissues with extranodal heterotopia are rare. In the head and neck region, different localizations of heterotopia of salivary gland tissues have been described, but the pterygopalatine fossa was not mentioned in the available sources. The difficulty of histological diagnosis when verifying heterotopia of the salivary glands may be due to the phenomena of chronic inflammation, lymphoid infiltration, tissue fibromatosis and the development of metaplasia. The rare occurrence of heterotopia of the salivary glands, the difficulties of its diagnosis and the lack of a unified approach to surgical treatment require consideration of each individually identified case.

The law of paired cases (also known as the law of series) is implemented in the interpretation of the presented clinical cases, when the identification of individual extraorgan foci of adenoid cystic cancer of the pterygopalatine space may be associated with a rare extranodal heterotopia of salivary gland tissue. The primary multiplicity of malignant lesions of the major salivary glands and heterotopia of salivary gland tissue can be both synchronous and metachronous. Adenoid cystic cancer of the pterygomaxillary fossa, as a component of multicentric growth of various localizations, clinically confirmed the recurrent nature of the course, the tendency to distant metastasis and generalization of the malignant process.