Secondary lymphoma involving metastatic follicular thyroid carcinoma to the skull: a unique example of tumor-to-tumor metastasis

Abstract

Tumor-to-tumor metastases to the skull, presenting as a scalp mass, and thyroid follicular carcinoma presenting in that location are extremely rare. We present the case of a patient with recently diagnosed retroperitoneal diffuse large B-cell lymphoma and an 8-year history of a non-tender large scalp-based mass. The scalp mass was an osteolytic enhancing lesion on imaging studies and diagnosed as metastatic thyroid carcinoma to the skull. The patient had no pre-existing history of thyroid cancer. This metastatic carcinoma was also secondarily involved with diffuse large B-cell lymphoma. This case illustrates a unique and previously unreported example of tumor-to-tumor metastasis in which both malignancies represent metastatic tumors to the skull with soft tissue extension presenting as a large scalp mass.

Keywords: Large cell lymphoma; Non-Hodgkin’s lymphoma; Skull metastasis; Thyroid carcinoma; Thyroid follicular carcinoma; Tumor-to-tumor metastasis.

Fig. 1

T1 weighted brain magnetic resonance images (a) with and (b) without contrast showing a partially intracranial, right parietal skull mass with diffuse heterogeneous contrast enhancement

Fig. 2

Metastatic follicular thyroid carcinoma to the skull with secondary involvement by diffuse large B-cell lymphoma. (a, b) Bland-appearing, variably-sized thyroid follicles containing colloid are infiltrated by large lymphoma cells (hematoxylin and eosin, (a) original magnification 100×, (b) original magnification 600×). (c) Follicular cells are immunoreactive for thyroid transcription factor 1 (TTF-1) (original magnification 600×) and (d) not CD20 (original magnification 600×)