Neuroendocrine tumors arising from the thymus itself account for just 2 to 5% of primary thymic malignancies [
8]. Atypical carcinoid is even a rarer type of neuroendocrine tumor [
3]. They mostly remain asymptomatic until they metastasize at the time of presentation (66% to lymph nodes from pulmonary origin) and behave as aggressive tumors rather than slow growing carcinoids. They are different from carcinoid tumors as they mostly arise in the foregut tissues such as bronchial epithelium and thymus gland. Patients usually have normal levels of serotonin and chromogranin-A in their blood and normal levels of 5-HIAA in their urine; however, they have raised levels of serotonin and 5-hydroxytryptophan (5-HTP) in their urine [
1,
3,
9].
There is a case report of atypical carcinoid originating from the thymus gland in the form of a mediastinal mass in association with hypercalcemia which was found to be due to parathyroid adenoma [
4]. Another case report of MEN 1 has shown ectopic parathyroid tissue in the mediastinal mass [
10] and another has reported thymic carcinoid with atypical course in such patients [
11]; however, very limited data are reported on the concomitant presence of parathyroid adenoma and asymptomatic metastatic mediastinal atypical carcinoid other than thymus. A single study has described a clear distinction between such a neuroendocrine tumor originating as ectopic tissue in the mediastinum rather than from a thymus gland [
1]. Our patient’s histopathology did not reveal any thymic tissue and has characteristic immunohistochemical staining for the neuroendocrine neoplasms, more specifically for atypical carcinoid tumor. The presence of sheets of cells in the parathyroid tissue (Fig.
3) of our patient presents the metastasis of atypical carcinoid tumor from the mediastinal ectopic neuroendocrine cells, which is a rare entity that has not been described before. Whether this can be the cause of parathyroid adenoma and hyperparathyroidism in our patient and what genetics could be involved is not much known. Besides parathyroid gland, it has also metastasized to lymph nodes, thyroid areas, and peripancreatic areas. Our patient had no clinical stigmata of carcinoid syndrome and has not had any airway obstructive disease (in view of large mediastinal mass). Further evaluation for pituitary tumor in the form of imaging was not possible due to financial limitations; besides, he did not have any clinical features of Cushing’s syndrome or acromegaly. Thus, our patient had multiple endocrine disorders with two neoplasms, of which one was aggressive with a guarded prognosis. Such a clustering can be very well explained as a variant of MEN syndromes and needs genetic analysis, which is not available in our region. Moreover, apart from everolimus therapy, which has been shown to improve prognosis in a trial [
12], the octreotide avidity of the metastasis in our patient means that our patient needs octreotide treatment as part of ongoing care, which has limitations in a resource-poor country.